1.0-specification.norg

@document.meta
title: The 1.0 Norg Specification
authors: [
    vhyrro
    mrossinek
]
categories: specifications
version: 1.0
@end

* Norg File Format Specification
  This file contains the formal file format specification of the Norg syntax version 1.0.
  This document is written in the Norg format in its original form and, thus, attempts to be
  self-documenting.

  Please note that this is *not* a reference implementation - this is an established rule set that
  should be strictly followed.

* Introduction
  Before diving into the details we will start with an introduction. The Norg file format was
  designed as part of the [Neorg]{https://github.com/nvim-neorg/neorg} plugin for Neovim which was
  started by /Vhyrro (@vhyrro)/ in April 2021. Soon after starting this work, /Max Rossmannek
  (@mrossinek)/ joined the development team, and, with the help of the [Neorg] community, the two
  have shaped the Norg syntax to what it has become today.

** What is Norg?
   The Norg syntax is a /structured/ plain-text file format which aims to be human-readable when
   viewed standalone while also providing a suite of markup utilities for typesetting structured
   documents. Compared to other plain-text file formats like e.g. Markdown, Org, RST or AsciiDoc, it
   sets itself apart most notably by following a strict philosophy to abide by the following simple
   rules:
   ~ *Consistency:* the syntax should be consistent. Even if you know only a part of the syntax,
     learning new parts should not be surprising and rather feel predictable and intuitive.
   ~ *Unambiguity:* the syntax should leave _no_ room for ambiguity. This is especially motivated by
     the use of [tree-sitter]{https://tree-sitter.github.io/tree-sitter/} for the original syntax
     parser, which takes a strict left-to-right parsing approach and only has single-character
     look-ahead.
   ~ *[Free-form]{https://en.wikipedia.org/wiki/Free-form_language}:* whitespace is _only_ used to
     delimit tokens but has no other significance! This is probably the most contrasting feature to
     other plain-text formats which often adhere to the
     [off-side rule]{https://en.wikipedia.org/wiki/Off-side_rule}, meaning that the syntax relies on
     whitespace-indentation to carry meaning.

   Although built with [Neorg] in mind, Norg can be utilized in a wide range of applications,
   from external note-taking plugins to even messaging applications. Thanks to its {* layers}[layer]
   system one can choose the feature set they'd like to support and can ignore the higher levels.

* Preliminaries
  First, we define some basic concepts which will be used in this specification.

** Characters
   A Norg file is made up of /characters/.
   A <character> is any Unicode [code point]{https://en.wikipedia.org/wiki/Code_point} or
   [grapheme]{https://www.unicode.org/glossary/#grapheme}.

*** Whitespace
    A {** characters}[character] is considered *whitespace* if it is any of the following:
    - The regular space `U+0020`
    - A tab `U+0009`
    - Any code point in the
      [Unicode Zs general category]{https://www.fileformat.info/info/unicode/category/Zs/list.htm}

    Any combination of the above is also considered whitespace.

    Tabs are not expanded to spaces and since whitespace has no semantic meaning there is no need
    to define a default tab stop. However, if a parser must (for implementation reasons) define a
    tab stop, we suggest setting it to 4 spaces.

*** Line Endings
    Line endings in Norg serve as a termination character. They are used e.g. to terminate
    {** paragraph segments}, {** paragraphs} and other elements like the endings of {** range-able
    detached modifiers}. They are not considered {*** whitespace}.

    The following chars are considered line endings:
    - A line feed `U+000A`
    - A form feed `U+000C`
    - A carriage return `U+000D`

    The following line ending combinations are permitted:
    - A single line feed
    - A single carriage return
    - A carriage return immediately followed by a line feed

*** Punctuation
    A {** characters}[character] is considered *punctuation* if it is any of the following:
    - A standard ASCII punctuation character: `|!"#$%&'()*+,-./:;<=>?@[\]^_`{|}~|`
    - Anything in the general Unicode categories `Pc`, `Pd`, `Pe`, `Pf`, `Pi`, `Po` or `Ps`.

*** Escaping
    A single {** characters}[character] can be escaped if it is immediately preceded by a backslash,
    `|\|` (`U+005C`). Any {** characters}[character] may be escaped /apart from/ {** characters}
    within free-form and ranged verbatim segments (see {** free-form attached modifiers} and
    {*** verbatim ranged tags}).
    For more information about precedence, take a look at the {* precedence} section.

*** Regular Characters
    Any other character not described by the preceding sections is treated as a generic code
    point/character.

** Words
   The Norg format is designed to be parsed on a word-by-word basis from left-to-right through the
   entire document /in a single pass/. This is possible because the language is [free-form], meaning
   that whitespace has no semantic meaning, and because the markup follows strict rules which are
   outlined in the later sections of this document.

   A *word* is considered to be any combination of {** characters} which are neither
   {*** whitespace} nor {*** punctuation} (see {*** regular characters}).

** Paragraph Segments
   {** Words} are first combined into *paragraph segments*. A paragraph segment may then contain any
   inline element of type:
   - {* attached modifiers}
   - {* linkables}

   Usually, a {*** line endings}[line ending] terminates the paragraph segment.
   This means that a paragraph segment is for the most part just a line of text:
   |example
   I am a paragraph segment.
   I am another paragraph segment.
   Together we form a paragraph.
   |end

   The exception to the rule is whenever a linkable or attached modifier within the paragraph
   segment spans more than a single line, in which case the paragraph segment also spans that
   distance. For example:
   |example
   I *am
   a long paragraph segment!*
   |end

** Paragraphs
   Paragraphs are then formed of consecutive {** paragraph segments}. A paragraph is terminated by:
   - A {$ paragraph break}
   - Any of the {* detached modifiers}
   - Any of the {** delimiting modifiers}
   - Any of the {** ranged tags}
   - Any of the {*** strong carryover tags}

   $ Paragaph Break
   A paragraph break is defined as an _empty line_. In the simplest case that means two consecutive
   {*** line endings} but since Neorg is a /free-form/ markup language, a line which only contains
   whitespace is also considered empty.

* Detached Modifiers
  Norg has several detached modifiers. The name originates from their differentiation to the
  {* attached modifiers}, which will be discussed later.

  All detached modifiers must abide by the following rules:
  - A detached modifier can _only_ occur at the beginning of the line (arbitrary {*** whitespace}
    (but nothing else!) may precede it)
  - A detached modifier must be immediately followed by {*** whitespace} or another detached modifier
    of the same type
  -- /NOTE/: The only exception to this is for the /closing/ modifier of the
     {** range-able detached modifiers}.

  The following table outlines all valid *detached modifiers*. It also adds various possible
  properties to each category which will be explained in more detail below.
  : . : Character
  : > : Name
  : > : Categories
  : _ : `*`
  : > : Headings
  :: >
     - Structural
     - Nestable
  ::
  : _ : `-`
  : > : Unordered Lists
  :: >
     - Nestable
  ::
  : _ : `~`
  : > : Ordered Lists
  :: >
     - Nestable
  ::
  : _ : `>`
  : > : Quotes
  :: >
     - Nestable
  ::
  : _ : `$`
  : > : Definitions
  :: >
     - Range-able
  ::
  : _ : `^`
  : > : Footnotes
  :: >
     - Range-able
  ::
  : _ : `:`
  : > : Table cells
  :: >
     - Range-able
  ::
  : _ : `%`
  : > : Attributes
  :: >
     - Nestable
  ::

** Structural Detached Modifiers
   The first detached modifier type is the /structural/ modifier type. As the name suggests,
   modifiers under this category *structure* the Norg document in some form or another.

   After a structural modifier, one {# paragraph segments}[paragraph segment] is consumed as the
   /title/ of the modifier.

   A property of structural detached modifiers is that they consume *all* other non-structural
   detached modifiers, lower-level structural modifiers, inline markup and {** paragraphs};
   they are the most important detached modifier in the hierarchy of modifiers.

   To manually terminate a structural detached modifier (like a heading) you must use a
   {** delimiting modifiers}[delimiting modifier]. Structural detached modifiers are automatically
   closed when you use another structural modifier of the same or lower level.

*** Headings
    |example
    * Heading level 1
    ** Heading level 2
    *** Heading level 3
    **** Heading level 4
    ***** Heading level 5
    ****** Heading level 6
    ******* Heading level 7 (falls back to level 6 in the tree-sitter parser)
    |end

    Although headings are both structural /and/ nestable (see next section), the former takes
    precedence over the latter, meaning that headings only affect a single
    {** paragraph segments}[paragraph segment] as their title. This is for user convenience as it
    does not require an empty line right below a heading. Because of this precedence, headings are
    also non-{** grouping}.

    Headings serve as a way to categorize and organize other elements into smaller chunks for better
    readability. They are currently the /only/ structural detached modifier present in the Norg
    syntax.

** Nestable Detached Modifiers
   Nestable detached modifiers are a kind which may be repeated multiple times in order to produce a
   _nested_ object of the given type. The nesting levels are capped at 6 in the [tree-sitter] parser
   but longer repetitions of the same modifier are allowed, falling back to the sixth nesting level.
   Other parsers may choose to support higher (or infinite) nesting levels.

   Furthermore, in contrast to most other (standard) {* detached modifiers}, this detached modifier
   type has /no/ title, and affects the following `paragraph` instead of only the next
   {# paragraph segments}[paragraph segment]. Said paragraph then becomes the modifier's /content/.
   This means that in order to terminate the detached modifier contents, you need an empty line (see
   {$ paragraph break}).

   Below you will find some examples of nestable detached modifiers.

*** Unordered Lists
    |example
    - Unordered list level 1
    -- Unordered list level 2
    --- Unordered list level 3
    ---- Unordered list level 4
    ----- Unordered list level 5
    ------ Unordered list level 6
    ------- Unordered list level 7 (falls back to level 6 in the tree-sitter parser)

    - Unordered list level 1
      This text is still part of the level 1 list item.
    -- Unordered list level 2
       This text is still part of the level 2 list item.
    --- Unordered list level 3
        This text is still part of the level 3 list item.
    ---- Unordered list level 4
         This text is still part of the level 4 list item.
    ----- Unordered list level 5
          This text is still part of the level 5 list item.
    ------ Unordered list level 6
           This text is still part of the level 6 list item.
    ------- Unordered list level 7 (falls back to level 6 in the tree-sitter parser)
            This text is still part of the level 7 list item.
    |end

    Unordered lists provide an easy way to enumerate items in an unordered fashion. Useful for data
    that's categorically similar but doesn't need to follow a strict order.

*** Ordered Lists
    |example
    ~ Ordered list level 1
    ~~ Ordered list level 2
    ~~~ Ordered list level 3
    ~~~~ Ordered list level 4
    ~~~~~ Ordered list level 5
    ~~~~~~ Ordered list level 6
    ~~~~~~~ Ordered list level 7 (falls back to level 6 in the tree-sitter parser)

    ~ Ordered list level 1
      This text is still part of the level 1 list item.
    ~~ Ordered list level 2
       This text is still part of the level 2 list item.
    ~~~ Ordered list level 3
        This text is still part of the level 3 list item.
    ~~~~ Ordered list level 4
         This text is still part of the level 4 list item.
    ~~~~~ Ordered list level 5
          This text is still part of the level 5 list item.
    ~~~~~~ Ordered list level 6
           This text is still part of the level 6 list item.
    ~~~~~~~ Ordered list level 7 (falls back to level 6 in the tree-sitter parser)
            This text is still part of the level 7 list item.
    |end

    This list type is only useful for data that needs to be kept in sequence. In contrast to other
    formats which may use a syntax like `1.`/`1)`, Norg counts the items automatically - this
    reduces complexity and makes reordering items simple.

*** Quotes
    |example
    > Quote level 1
    >> Quote level 2
    >>> Quote level 3
    >>>> Quote level 4
    >>>>> Quote level 5
    >>>>>> Quote level 6
    >>>>>>> Quote level 7 (falls back to level 6 in the tree-sitter parser)

    > Quote level 1
      This text is still part of the level 1 quote.
    >> Quote level 2
       This text is still part of the level 2 quote.
    >>> Quote level 3
        This text is still part of the level 3 quote.
    >>>> Quote level 4
         This text is still part of the level 4 quote.
    >>>>> Quote level 5
          This text is still part of the level 5 quote.
    >>>>>> Quote level 6
           This text is still part of the level 6 quote.
    >>>>>>> Quote level 7 (falls back to level 6 in the tree-sitter parser)
            This text is still part of the level 7 quote.
    |end

    Quotes are rather self-explanatory - they allow you to cite e.g. a passage from another source.

*** Attributes
    |example
    % attrib1
    %% attrib2
    %%% attrib3
    %%%% attrib4
    %%%%% attrib5
    %%%%%% attrib6
    |end

    Attributes are detached modifiers that exist solely for the purpose of having altered behavior
    through {** carryover tags}. These can then be referenced within {** attached modifier extensions}
    and the tags applied to the attribute will be applied to the attached modifier with said attribute.

    These modifiers can be nested to create a hierarchy of attributes. Below is an example of this
    in action:
    |example
    % color
    +color #FF0000
    %% red
    +color #00FF00
    %% green
    +color #0000FF
    %% blue

    This will be /red/(color:red), /green/(color:green) and /blue/(color:blue).
    |end

**** Limits
     You can impose limits on where the attribute can be used through the `attribute-limits` tag,
     which should be placed before the attribute definition. The tag takes in a list of the following
     parameters:
     - `none` - no limits
     - `verbatim` - can be used only for the \`verbatim\` attached modifier
     - `math` - can be only used on the \$mathematics\$ attached modifier
     - `macro` - can be only used on the inline \&macro\& attached modifier
     - `links` - can only be used on links (this includes anchors)
     - `non-verbatim` - for all the other non-verbatim attached modifiers (bold, italic, subscript,
       superscript, underline, the null modifier etc.)

     These limits can be chained, i.e. `#attribute-limits links non-verbatim`.

*** Invalid Nestable Detached Modifier Examples
    |example
    >I am not a quote

    some preceding text > I am also not a quote

    >- I am not a valid detached modifier

    > > I am only a level 1 quote

    *
        I am not a valid heading title.
    |end

** Range-able Detached Modifiers
   Range-able detached modifiers can occur in two forms:
   - As a single detached modifier in which case they affect:
   -- The next `paragraph_segment` which becomes the /title/
   -- Any following paragraph which becomes the /content/
   - As a pair of two detached modifiers in which case:
   -- The next `paragraph_segment` also becomes the /title/
   -- The content continues until the "closing" detached modifier is found

   The closing modifier has the same rules as an opening detached modifier except it /must/ be
   directly succeeded by a {*** line endings}[line ending] in contrast to the whitespace character which must follow the
   opening modifier.

*** Definitions
    Definitions are primarily of use to people who write technical documents.
    They consist of a term, and then are followed by a definition of that term.

    |example
    $ Term
    Definition content.
    |end

    To create longer definitions, use the ranged definition syntax instead:
    |example
    $$ Term
    Content of the definition.

    Which scans up to the closing modifier.
    $$
    |end

*** Footnotes
    Footnotes allow the user to give supplementary information related to some text without
    polluting the paragraph itself. Footnotes can be linked to using {* linkables}.

    |example
    ^ Single Footnote
    Optional footnote content.
    |end

    To create longer footnotes, use the ranged footnote syntax instead:
    |example
    ^^ Ranged Footnote
    Content of the footnote.

    Which scans up to the closing modifier.
    ^^
    |end

*** Table Cells
    Table cells are used to, well, build up a table. Here are a few examples of table cells:
    |example
    : A1
      Content of table cell at `A1`.
    :: A2
    > Content of table cell at `A2` (in a quote).
    ::
    |end
    Their semantics are described in more detail in the {:1.0-semantics:* Tables}[semantics] document,
    which we recommend reading if you are interested in the behavior of objects as opposed to how
    they are defined.

    *NOTE*: In order to make tables more aesthetically pleasing, they're commonly mixed with the
    {* intersecting modifiers}[intersecting modifier] syntax to produce the following:
    |example
    : A1 : Content of table cell at `A1`.
    |end

** Grouping
   Both nestable and range-able detached modifiers have a unique quality - when several consecutive
   modifiers /of the same type/ are encountered (by consecutive we mean _NOT_ separated via a
   {$ paragraph break}), they are treated as one whole <object>. This is crucial to understand as
   it is required for the many types of {** carryover tags} to function.

*** Examples
    |example
    The following items naturally group because they are range-able, for example forming a
    definition list:
    $ Term 1
      Definition 1!
    $ Term 2
      Definition 2!
    |end

    |example
    Together, these form one whole unordered list:
    - List item 1
    - List item 2
    |end

    |example
    - List item in one list

    - This item is in another list, because we used a {$ paragraph break} to split these items
    |end

** Delimiting Modifiers
   In Norg, {** structural detached modifiers} and {*** indent segment}s may be terminated by a
   delimiting modifier. This kind of modifier must abide by the following rules:
   - A delimiting modifier can _only_ occur at the beginning of the line (arbitrary {*** whitespace}
     (but nothing else!) may precede it)
   - A delimiting modifier must consist of two or more consecutive modifiers of the same
     type (a single character cannot be used to avoid false-positives /during/ the typing process;
     plus a single character can look quite confusing/ugly when used like this...)
   - A delimiting modifier must be followed by an immediate {*** line endings}[line ending] (without any extra
     {*** whitespace}; this disambiguates them from nestable detached modifiers like for example an
     unordered list item vs. the `--` delimiting modifier)

*** Weak Delimiting Modifier
    This modifier uses the `-` character and immediately closes the /current/ nesting level
    (decreases the current nesting level by one).
    |example
    * Heading level 1
      Text under first level heading.

    ** Heading level 2
       Text under second level heading.
       ---

      Text under first level heading again.
    |end

*** Strong Delimiting Modifier
    This modifier uses the `=` character and immediately closes all nesting levels.
    |example
    * Heading level 1
      Text under first level heading.

    ** Heading level 2
       Text under second level heading.
       ===

    Text belonging to no heading level (i.e. belonging to the document's root).
    |end

*** Horizontal Rule
    This modifier uses the `_` character and simply renders a horizontal line. It does _NOT_
    affect the heading level but immediately terminates any {** paragraphs}[paragraph].
    |example
    * Heading level 1
      Text under first level heading.
      ___
      This is a new paragraph separated from the previous one by a horizontal line.
      This text still belongs to the first level heading.
    |end

** Detached Modifier Extensions
   {* Detached modifiers} support extensions which must immediately follow the detached modifier
   (or another extension). Note that {* detached modifiers} must be succeeded with {# whitespace},
   therefore by "immediately followed" we mean /after/ the whitespace character in the detached
   modifier, e.g. `- (x) List item`(lang:norg).

   The syntax is as follows:
   - An extension starts with a `(` char
   - Immediately a special character must follow. This character determines the type of extension.
   - Some extensions can support parameters - if this is the case, the special character must be
     followed with {# whitespace} after which the parameters (a sequence of {** words} and/or
     newlines) ensue.
     Not all extensions support parameters and for good reason. There is no need to attach extra
     metadata to a done or undone state for instance. Several extensions should be delimited with
     the {* contextual `|` delimiter}.
   - A `\|` character may be matched, which allows the user to chain many extensions together, e.g.
     `(x|# A)`(lang:norg) (done with a priority of A).
   - Finally a `)` char closes the extension.

   NOTE: The whole detached modifier extension /must/ be followed by whitespace.

*** TODO Status Extension
    The TODO item extension assigns a task status to a certain modifier. You probably know this
    concept from Org where unordered lists can become tasks. In Norg we take this concept to
    the next level because any detached modifier can be assigned a task status. This can for
    example be useful for the author of a document to keep track of the status of certain sections.

    The following characters are reserved for the TODO status extension:
   -- `| |`: undone (a literal space)
   -- `x`: done
   -- `?`: needs further input/clarification
   -- `!`: urgent
   -- `+`: recurring (with an optional {**** timestamp extension}[timestamp])
   -- `-`: in-progress/pending
   -- `=`: on hold
   -- `_`: put down/cancelled

    Some examples include:
    |example
    - ( ) Undone
    - (x) Done

    - (# B| ) Undone with a priority of B
    - (+) Recurring
    - (+ 5th Jan) Recurring every 5th of January
    |end

*** Advanced Detached Modifier Extensions
    Apart from just being able to assign a TODO state it is also possible to apply more complex
    states with parameters to certain indicators. Such examples are the {**** timestamp extension}
    and the {**** priority extension}.
    In the following sections you will find descriptions for a few other extensions supported within
    Norg.

**** Timestamp Extension
     The timestamp extension allows you to associate a {* detached modifiers}[detached modifier]
     with a date/time.
     The syntax for a timestamp is as {^ note to parser developers}[follows]:
     `<day>?,? <day-of-month> <month> -?<year> <time> <timezone>`
     - ::
       The `<day>` value is reliant on the current locale, but the following alterations of that
       value are permitted:
       -- Full version (e.g. `Tuesday`, `Wednesday`)
       -- An unambiguous shorthand (a shorthand that can uniquely identify the day), e.g. `Tue`, `We`,
          `M` (Monday), `Frid`. Something like `T` is not allowed, as both `Tuesday` and `Thursday`
          could satisfy the input.

       The value may also be omitted if one chooses.
     - The `,?` expression means that a `,` character may optionally exist in that location.
     - The `<day-of-month>` value is simply a numeric value with at most 3 digits (to disambiguate
       it from the `<year>` value).
     - The `<month>` value is a word-based representation of the current month (i.e. `October`,
       `January` etc.) dependent on the current locale. The same shorthand rules apply as in the
       `<day>` value.
     - The `<year>` value must be a numeric value with at least 4 digits (for dates before `1000`,
       prefix the year with the appropriate amount of zeroes, so for example the year `200` should
       be written as `0200`). The `<year>` value may also be prefixed with a `-` (negative) sign to
       differentiate `B.C` from the default `A.D`.
     - The `<time>` value must consist of this format (in regex): `|\d{1,2}:\d{2}(\.\d{1,2})?|`.
       Some examples would be: `18:00`, `5:32`, `00:12.32`.

     Obviously, you're not required to type the whole syntax out every time. Any of the elements in
     angled brackets (`<>`) can be dropped/ignored, but the order of those values may not change!
     Some examples of valid timestamps include:
     - `Sat, 29 Oct 1994 19:43.31 GMT`
     - `We 12th Jan 2022`

     Apart from just being able to supply a timestamp, you are also permitted to provide a <range>.
     The syntax is simple, and is contained within the extension:
     |example
     {@ 5th Aug 2022 - 20th August 2022}
     {@ 5th Aug 2022-20th August 2022} <- Also valid
     |end
     You can even omit some fields from either one of the sides like so:
     |example
     {@ 5th - 20th August 2022}
     |end
     The matching fields will be automatically completed based on the information of the other half.

     ^ Note to Parser Developers
     It should be mentioned that a parser of the Norg format is not required to perform any
     timestamp analysis further than detecting what set of characters contain a timestamp.
     The actual interpretation of its internal fields and the interpretation of a {# range} are the
     responsibility of the *semantic analyzer* (see also the [semantics document]{:1.0-semantics:}).

**** Priority Extension
     This extension allows you to specify a priority of your detached modifier extension.

     Syntax:
     |example
     * (# A) This heading has priority A (highest priority)
     |end
     Note that Norg does not specify strict semantics for this detached modifier extension, and as
     such there is no set-in-stone way to specify priorities. The most common (and recommended) way
     to specify priorities is to go from `A-Z`, but many also prefer `0-9` or even named priorities
     like `LOW`\/`MEDIUM`\/`HIGH`.

     [Neorg]'s [GTD]{https://hamberg.no/gtd} implementation even repurposes the priority for use as
     contexts, so yes, this detached modifier extension is very versatile.

**** Due Date Extension
     As the name suggests, this extension marks something as "due before x", where x is a
     {**** timestamp extension}[timestamp]. Especially useful in [GTD] and other forms of note-taking and time management applications.

     Syntax:
     |example
     - (< Tue 5th Feb) Do this before the 5th of February.
     |end

**** Start Date Extension
     A counterpart to the {**** due date extension} - defines when a task *begins*, also useful in
     [GTD].

     Syntax:
     |example
     - (> Tue 5th Feb) This task starts after the 5th of February.
     |end

** Detached Modifier Suffix
   Since {# nestable detached modifiers} can only contain a {# paragraphs}[paragraph] this can
   cause severe limitations because the insertion of e.g. code blocks is not possible. To alleviate
   this deficiency, the {** detached modifier suffix} exists, which temporarily increases the
   current indentation level to allow complex nested items within.

   There are two variations of the indent segment, the {# slide} and the {# indent segment}.
   *NOTE*: After a detached modifier suffix is matched (either `:` or `::`) a {*** line endings}[line ending] must
   follow /instantly/.

*** Slide
    The slide, denoted with a single `:`, allows for a set of contiguous /complex items/ below:
    |example
    - :
      This is some text.
      $ Term
        And this is the term's definition.
    |end

    These <complex item>s may be any *non-{** structural detached modifiers}[structural]* detached
    modifier, {* tags}[tag] or paragraph.

    To terminate a slide, one of two conditions must be met:
    - A {$ paragraph break} is encountered.
    - If the slide is part of a {** nestable detached modifiers}[nestable detached modifier], when
      an item of the same or lower level is encountered below.

**** Examples
***** Terminating via a {$ Paragraph Break}
      |example
      - :
        This is part of the list item.
        @code lua
        print("This is also a part of the list item")

        -- Despite the fact that there is a double newline dividing the `print` statement and this
        -- comment, it is not a paragraph break, therefore it does not terminate the slide.
        @end
        $ Term
        Here is a definition!

      Now that there is a {$ paragraph break} between this paragraph and the previous item
      this paragraph no longer belongs to the slide.
      |end

***** Terminating as Part of a Nestable Detached Modifier
      |example
      -- :
         Content of the slide.
      - Because this item is a level lower than the item containing the slide above
        the slide is terminated.
      |end

*** Indent Segment
    The indent segment, denoted with two colons (`::`), creates a ranged version of the slide.
    This indent segment must be closed with any of the {** delimiting modifiers}, or an element of
    the same type with the same or lower nesting level. By "lower" nesting level we mean higher up
    in the hierarchy of nodes, or in other words `unordered_list_level_1` is "lower" than an
    `unordered_list_level_2` item, because it is nested less.

    The indent segment may contain an arbitrary amount of {# complex item}[complex items].

    Examples:
    |example
    - ::
      This is some content.

      $ Term
        Definition.
    - This is the second item of the list.
      The indent segment did not need to be terminated.

    - ::
      This is another list.

      |details
      *hello* world!
      |end

      -- This is a nested item in the indent segment
      -- And so is this.

      But you can still continue your content here.
      ---

    Since there was no other item of the same type after the indent segment
    it must be closed with `---` or `===`.
    |end

* Tags
  The main differentiator from simple markup formats and more complex ones is the ability to define
  data and extensions for the format. Norg allows for you to extend its syntax and define data
  within clear boundaries - it does this using tags.

  *NOTE*: Tags are the /only/ way that extensions may be made to the format.

  There are 6 different tag types, each with their own way of changing the way text in Norg is
  interpreted. Before we discuss those, however, we should discuss the syntax rules for tags:
  - A tag is similar to a {# detached modifiers}[detached modifier] in the sense that it must begin
    at the beginning of a line with optional {*** whitespace} (but nothing else) preceding it.
  - After that you will encounter a special tag character (`=`, `|`, `@`, `#`, `+` and `.`), /none/
    of which are attached modifiers (see {^ disambiguating tags and attached modifiers}). The
    special tag character is then /immediately/ followed by text, which becomes the /tag name/. Said
    tag name can consist of any {# regular characters}[regular character] and/or `-` and `_`.
  - Tags can have their names delimited by a `.` in order to create a "hierarchy", e.g.
    `document.meta`.
  - ::
    After a {*** whitespace} character any number of parameters on the same line may follow:
    |example
    #tag-name.subtag parameter1 parameter2
    |end
    By default parameters are space-separated. In order to create multi-word parameters, you may
    escape the space character with a backslash (`\`).
    |example
    #tag-name.subtag parameter1\ with\ spaces parameter2
    |end
    Parameters may consist of any character (apart from a {*** line endings}[line ending], of course).
    ---

  ^ Disambiguating tags and attached modifiers
    If tag characters were attached modifier openers there would be no way to know whether the
    character is an attached modifier opener or a tag opener until the whole line has been parsed;
    in other words, such a scenario would entail a difficult to resolve ambiguity.

  Norg provides several inbuilt tag names that are reserved, but their details are not explained
  in this specification - this document strictly covers syntax - see the [semantics document] for a
  list of the built-in tags. There is no restriction in regard to the length of a tag name, nor are
  there any disallowed names that a parser should omit (unless they don't adhere to the above rules
  regarding tag names).

** Ranged Tags
   Ranged tags are a way to express custom information within a range.
   They begin with the traditional tag declaration and are ended with an `end` statement.

   The `end` statement has a simple rule set:
   - Must be at the start of a line, may be preceded by any {*** whitespace} (but nothing else)
   - Must use the same prefix as its parent (in the case of standard ranged tags: `|`; in the case
     of verbatim tags: `@`; for macro tags: `=`)
   - Must *immediately* be succeeded by a {*** line endings}[line ending].

*** Macro Tags
    Macro tags (also known as /macro definitions/) are a tag type designed to declare and define
    macros. Macros are templates that can be executed with parameters in order to place some
    structured text into the document.

    The content of the macro tag is /any/ Norg markup - this includes {** structural detached
    modifiers} and nested {* tags}. The macro tag is closed with the `=end` statement.

    Under the hood, all other {* tags}[tag] types are implemented as macros with special parameters
    and contents.

    The following is an example of a macro:
    |example
    =see url
    (see {&url&})
    =end
    |end

    It can then be invoked using any of the other tag types, for example the {** infirm tag}:
    |example
    This is a recipe for a cake
    .see https://wikipedia.com/some-cool-cake-recipe
    \- let's begin cooking!
    |end

    After macro expansion, this is what the document would look like:
    |example
    This is a recipe for a cake
    (see {https://wikipedia.com/some-cool-cake-recipe})
    \- let's begin cooking!
    |end

    Which, when reformatted, would look (and render) like so:
    |example
    This is a recipe for a cake (see {https://wikipedia.com/some-cool-cake-recipe}) - let's begin
    cooking!
    |end

*** Standard Ranged Tags
    There are times when you may want to create an isolated block of Norg markup.
    To do this you may use the standard ranged tag, which uses the `|` character.

    Currently, it is only used for four tags, `comment`, `example`, `details` and `group`:
    - The `comment` ranged tag is used for long strings of comments (versus the `%` null attached
      modifier, which is mostly used for short comments).
    - The `example` tag is a simple way to show an example of some Norg markup without it being
      rendered and treated as physical markup (most commonly used throughout this very document to
      show unrendered examples of Norg syntax).
    - The `details` tag is a way to hide away markup (just like
      {https://developer.mozilla.org/en-US/docs/Web/HTML/Element/details}[`<details>`] in HTML).
      - The `group` tag may be used to group together many elements and apply a global {*** strong
        carryover tags}[strong carryover tag] to each one of them.

**** Examples
     `\|example`:
     |example
     |example
     * This is an example heading.
     |end
     |end

     `\|comment`:
     |example
     |comment
     This is a very long comment with some content
     and with some markup!

     * Heading
       /italic/ and *bold*.
     |end
     |end

     `\|details`:
     |example
     |details
     * Here is some hidden markup!
       Wowzers.
     |end
     |end

     `\|group`:
     |example
     #color red
     |group
     This will be red.

     So will this.

     * So will this
       And this.
     |end
     |end

**** Edge Cases and Semantic Interpretation
     A commonly arising question is "how are these interpreted at parse time?" - can you link to
     elements within `\|comment` tags? What governs the behavior of these differing tags?

     The answer may be illustrated simply by showing how these tags are implemented.
     As mentioned in the {*** macro tags} section, all tag types (apart from the macro tag) are a
     macro invocation under the hood. Below are the implementations for `\|comment` and `\|group`,
     respectively:
     - :
       |example
       =comment ...
       =end
       |end
     - :
       |example
       =group ...
       &...&
       =end
       |end

     The `\|comment` tag evaluates to /no value/. Anything that is placed within a comment during
     invocation (the `...` parameter) is simply dropped. Because of this it is *not* possible to
     link to elements within comment tags. The `\|group` tag returns everything that you give
     it, because of this it *is* possible to freely link to any element within a `\|group`.

     To summarize - the behavior of each individual standard ranged tag is fully governed by its
     implementation - see the [semantics document] for more details.

*** Verbatim Ranged Tags
    In other cases you may be more interested in an isolated block /without/ Norg markup (i.e. a
    /verbatim/ block). A prime example of this is `@code`, which creates a code block - you
    obviously don't want nested Norg syntax within that! Note how in the following example the
    `@MyAnnotation` would clash with Norg's verbatim ranged tag syntax, but doesn't as no nested
    markup is allowed within:
    @code java
    @MyAnnotation(name="someName", value="Hello World")
    public class TheClass {
      // ...
    }
    @end
    This ranged tag type is the most commonly used one as it has the widest range of applications.
    The {*** standard ranged tags}[standard ranged tag] is a much more niche syntax element targeted
    at specific use cases.

** Carryover Tags
   Carryover tags are a construct used to assign certain properties to the next item or whole
   {# objects}[object].

   /Note/: Internally, they are a type of {** macro tags}[macro tag], where the next element is given
   as the last parameter to the macro. For more info see {*** macro tags} and the [semantics document].

   There are two types of carryover tag, the {*** weak carryover tags}[weak carryover tag] and the
   {*** strong carryover tags}[strong variant].

*** Weak Carryover Tags
    The weak carryover tag affects the next element and next element /only/. It does not work with
    whole collections of elements (see {*** strong carryover tags}).

    Weak carryover tags only apply to the next element; their behavior is as follows:
    - When the element has children, the weak carryover tag only applies to the single item (it does
      not carry over to its children).
    - When the element is part of an {# object}, no items other than the one below the weak
      carryover tag is affected.
    - An exception is made when a weak carryover tag is applied to an {# indent segment} or a
      {** ranged tags}[ranged tag], in which case everything within that segment/tag is affected.

**** Examples
     Only the second item is affected:
     |example
     - List item 1
     +color red
     - List item 2 (which is red)
     - List item 3 (which is normal-colored)
     |end

     Only the `Heading 1` and `This is some content` text is highlighted:
     |example
     +color red
     * Heading 1 (which is red)
       This is some content. (which is still red)
     ** Heading 2 (which is normal-colored)
        This is also some content. (which is normal-colored)
     |end

     Special behavior for indent segments:
     |example
     - List item 1
     +color red
     - List item 2 (which is red)
     -- But this isn't red
     -- Neither is this
     +color green
     - ::
       This is green.

       -- This is also green
       -- And so is this.
       ---
     |end

*** Strong Carryover Tags
    Contrary to its {*** weak carryover tags}[weak variant], the strong carryover tag exists to
    annotate an entire {# object} versus just a single item. Its behavior is opposite to its weak
    counterpart, namely:
    - When the element has children, the strong carryover tag applies to both the whole item and all
      of its children.
    - When the element is part of an {# object}, all items in the object are affected.

**** Examples
     A nice use case is the `#choice` carryover tag, which converts all items in a list into a
     single-choice question with right/wrong answers:
     |example
     What is your favorite activity? Hint: there's only one correct answer :)
     #choice
     - ( ) Sleeping
     - ( ) Learning
     - (x) Writing `.norg` documents
     |end

     Here, both the level 1 heading and the level 2 heading along with their contents will be
     colored red:
     |example
     #color red
     * Heading 1
       This is some content.
     ** Heading 2
        This is also some content.
     |end

*** Carryover Tags and Paragraphs
    A feature of {** carryover tags} which we have not discussed yet is how they interact with
    {** paragraphs} (and {** paragraph segments}). The following simple rules apply:
    - {*** strong carryover tags} affect the next {** paragraphs}[paragraph]
    - {*** weak carryover tags} affect the next {** paragraph segments}[paragraph segment]

    For example:
    |example
    #color blue
    This entire paragraph
    will now appear in blue
    color.

    This next paragraph is normal-colored.
    +color red
    But this single line is colored red,
    whereas this line is normal-colored again.

    #color blue
    This part is blue,
    +color red
    but the latter carryover tag takes precedence, making this part red,
    and this part blue again, since the weak carryover tag does not affect this segment.
    |end

** Infirm Tag
   The infirm tag is the simplest form of executing a macro. It is a single-line, embeddable macro
   invocation with the ability to supply parameters. It is denoted with the `.` character.

   Below is an example:
   |example
   =LoremIpsum
   Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut
   labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris
   nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate
   velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non
   proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
   =end

   This is a paragraph, and below you will find the lorem ipsum text:
   .LoremIpsum
   This is still the same paragraph (assuming the macro invocation only inserted text; which it did
   in this specific example).
   |end

* Attached Modifiers
  This section discusses attached modifiers (which originally gave rise to the name of {* detached
  modifiers} as their natural counter-parts). Attached modifiers encapsulate some text within a
  {** paragraphs}[paragraph] and change the way it is displayed in the document.
  An attached modifier consists of two parts: the /opening modifier/ and the /closing modifier/.

  Below are the general rules for attached modifiers:
  - An opening modifier may only be preceded by {# whitespace} or {# punctuation}
  - An opening modifier may _NOT_ be succeeded by {# whitespace}
  - A closing modifier may _NOT_ be preceded by {# whitespace}
  - A closing modifier may only be succeeded by {# whitespace} or {# punctuation}
  +name attached modifier range
  - ::
    {* Attached modifiers} can only span at maximum a single {# paragraphs}[paragraph], i.e. they get
    terminated as soon as they encounter a {$ paragraph break}.

    This means that this:
    |example
    *this

    text*
    |end
    will *not* result in any bold text, as it's divided by a {$ paragraph break}.
    However, this:
    |example
    *this
    text*
    |end
    is fine, and will result in *`this text`* being bold.
  - Nested {* attached modifiers} should be closed in the opposite order they were opened.
  - Two or more consecutive attached modifiers of the same type (i.e. `**`, `//` etc.) should be
    instantly "disqualified" and parsed as raw text in /all/ circumstances and without any
    exceptions.

  Their name should be rather self-explanatory - both the opening and closing modifier are
  /attached/ to one another.

  The following attached modifiers exist and have respective meaning:
  - \*bold\*: *bold*
  - \/italic\/: /italic/
  - \_underline\_: _underline_
  - \-strike-through\-: -strike-through-
  - \!spoiler\!: !spoiler!
  - \^superscript\^: ^superscript^ (cannot be nested into `subscript`)
  - \,subscript\,: ,subscript, (cannot be nested into `superscript`)
  - \`inline code\`: `inline code` (disables any nested markup - verbatim)
  - \%{** Null Modifier}[null modifier]\%: %null modifier%
  - \$inline math\$: $f(x) = y$ (verbatim)
  - \&variable\&: &variable& (verbatim)

** Valid Examples
   |example
   *Bold text*

   *Bold text*,
   .*Bold text*,

   *Bold
   text*

   */Bold and italic/* <- closing modifiers closed in the opposite order they were opened
   */Bold and italic/ and only bold*

   Text */with/ _different_ ^markup^ !types!*
   |end

** Invalid Examples
   |example
   * Bold text *

   *Bold text *

   other text*Bold text*

   *Bold text*other text

   *
   Bold text*

   *Bold
   text
   *

   *Bold

   text*

   Closed in the wrong order:
   */Bold and italic*/

   Also closed in the wrong order:
   */Bold and italic* and only italic/
   |end

** Null Modifier
   This section expands a bit on the concept of the `%null modifier%` in order to understand
   some of its use cases.

   When used in a standalone fashion, the null modifier nullifies (removes) all of the text inside.
   This means that on its own it behaves like a comment, which is never rendered:
   |example
   Cats %TODO: create section about cats% are very cute animals.
   |end

   In higher {* layers}, this modifier can have its behaviour extended with the {** attached modifier
   extensions}[attached modifier extension] syntax, which essentially makes it a configurable
   modifier suit for many occasions. For example, if you wanted to make an arbitrary part of your
   text red, you may do:
   |example
   This part of the text is %colored red%(color:red)!
   |end

** Variables
   Variables are a {** layer 5} attached modifier that allow a user to invoke a macro without any
   parameters and place the result inside e.g. a paragraph. For more information on their
   behavior see the [semantics document].

** Free-form Attached Modifiers
   Even with all the rules described in the above sections there are still some evident limitations
   with attached modifiers, namely:
   - Arbitrary {*** whitespace} within {* attached modifiers} is not permitted: `*  bold  *` is
     invalid and thus not bold.
   - Representing verbatim attached modifier chars within the corresponding verbatim blocks is not
     possible: `|`I cannot place a (`) char inside here without accidentally terminating the
     block.|`.

   Free-form modifiers fix this with a special syntax to specify the beginning and end of a ranged
   block. For example:
   |example
   Here, I can write `| leading and trailing whitespace (with a ` char)  |` within a verbatim block
   without accidentally terminating it.

   Here, I can use a literal `$` inside inline math: $| 10$ + 10$ = 20$ |$.
   |end

   The use of pipes is special because the position of the pipe (i.e. whether it's before or after the
   attached modifier) can unambiguously tell us whether that symbol is an opening attached modifier
   or a closing one. It's thanks to this that whitespace is freely allowed within its content.

   Aside from the details described above, free-form attached modifiers have the following properties:
   - Backslashes (`\`) are treated as verbatim and do not mean an {*** escaping}[escape sequence]
     (see {* precedence}).
   - Despite being called "free-form" they can still only span a single paragraph (see {# attached
     modifier range}).

** Link Modifier
   The link modifier, `:`, is a special modifier type - it puts a twist on the original attached
   modifier rules - in fact, it's the polar opposite.

   As described in the {* attached modifiers} section, attached modifier types may not exist
   in between words like so:
   |example
   abso/freaking/lutely!
   |end

   It's entirely plausible to want to do this however, which is why the {** link modifier}[link
   modifier] was devised. With it, you can bridge attached modifiers and regular text together:
   |example
   abso:/freaking/:lutely!
   |end

   It is important to note that link modifiers do not need to occur in pairs. This:
   |example
   Ex:*ample* text
   |end
   Will also result in `ample` becoming *bold*. In fact, using a link modifier at the end will not
   give the desired result (it will be rendered as a regular `:` char). To understand why keep
   reading.

   Through the examples above it is evident that there are two link modifier types: one where the
   link modifier is an /opening/ link modifier (i.e. it appears before an opening attached modifier)
   and one where it's a /closing/ link modifier (i.e. it appears after a closing attached modifier).
   This distinction is visible even when they don't occur in pairs.

   In the case that the link modifier is opening (the attached modifier appears on the right):
   - The link modifier may only be preceded by a {# regular characters}[regular character]
     (or, in other words, may /not/ be preceded by a {*** punctuation} character nor by a
     {*** whitespace} character).
   - The link modifier may only be succeeded by an opening attached modifier.

   In the case that the link modifier is closing (the attached modifier appears on the left):
   - The link modifier may only be preceded by a closing attached modifier.
   - The link modifier may only be succeeded by a {# regular characters}[regular character].

   If the above conditions are not met, then the character should be treated as a literal `:`.

** Attached Modifier Extensions
   Similarly to {** detached modifier extensions}, attached modifier extensions serve as a way
   to attach metadata to {* attached modifiers}.
   The metadata that you can attach, however, differs from {** detached modifier extensions}, as they
   serve different use cases.

   The content of attached modifier extensions consists of a set of references to many
   {*** attributes}. These attributes are delimited by the {* contextual `|` delimiter}.
   If the attribute is part of a hierarchy (see {*** attributes}), you may use the `:`
   character to link them together. Some inbuilt attributes are the `lang` and `color` hierarchies
   (a comprehensive list can be found in the [semantics document]).

*** Examples
    |example
    `print("This is some python")`(lang:python) <- The lang:python attribute highlights the text as python
    *some green and bold text!*(color:green)    <- some green and bold text

    {* Link location}[this is an important link](important|color:red) <- Highlights the link as big,
                                                                         bold (important) and red.
    |end

* Contextual `|` Delimiter
  The pipe (`|`) character is a really nice character - it can be applied to many problems
  and expressively represent certain behaviors, specifically /delimiting/. While also used for
  {*** standard ranged tags} and {** free-form attached modifiers}, the pipe symbol is also used as
  a delimiter for {** Detached Modifier Extensions}[detached] and {** Attached Modifier
  Extensions}[attached] modifier extensions. Even though it's used 3 times for different purposes,
  the contexts in which they are used in allows for them to be unambiguous. It also keeps intent
  consistent across the format.

* Intersecting Modifiers
  Norg is a syntax designed to be used by many - this includes many styles and preferences. Although
  it's impossible to satisfy everyone, there are some variations of syntax that can be used to
  "beautify" Norg markup.
  The intersecting modifier does just that - it's a way to intersect two different paragraph
  segments (and *only* paragraph segments) together on the same line.

  The syntax is as follows:
  - First, a {*** whitespace} character must be matched
  - Next, the actual modifier (currently only `:`) must be matched.
  - The token ends with another {*** whitespace} character.

  The use case for the intersecting modifier is best illustrated by example:
  |example
  $ Term
    This is a definition of that term.
  |end
  This is perfectly normal syntax that you would write day to day in Norg. But what if you're more
  of a fan of one-liners? The `| : |` intersecting modifier (currently the only modifier of this
  type) can be used to do just this:
  |example
  $ Term : This is a definition of that term.
  |end
  This syntax is especially favored for {*** table cells}:
  |example
  : A1 : Content of the cell at A1
  : A2 : Content of the cell at A2
  |end

  The `| : |` syntax expands to a newline, which means that after expansion you get:
  |example
  : A1
  Content of the cell at A1
  : A2
  Content of the cell at A2
  |end

* Linkables
  Finally, there is one more kind of inline syntax which is the {# linkables} kind.
  Linkables can link to any element /anywhere/ in the document.

  When resolving links, the first match should always be the only match, starting from the top of
  the document and heading towards the bottom. This means that if there are two matches, the one at
  the topmost part of the document should be chosen as the target.

  Linkables are comprised of many segments, and can change meaning depending on the order those
  segments were defined in.

  Linkables are essentially a more lenient version of the {* attached
  modifiers}[attached modifier] syntax. Below are the rules for linkables:
  - An opening modifier may be instantly succeeded with anything /but/ a {#
    line endings}[line ending].
  - A closing modifier may *not* be preceded by a {# line endings}[line ending].

  Below are a few examples of invalid linkables:
  |example
  this is not a {
  * linkable}

  nor is this a [linkable
  ]

  <
  this certainly isn't a linkable
  >
  |end

  *An unclosed linkable may be treated as an error in the resulting syntax tree*.

** Link Location
   The link location is defined through curly braces (`{}`) and contains the physical location
   that the user would like to link to. Inside these curly braces you can find one (or more; with
   limited inter-compatibility) of the following types of data:
   - A {# file location}
   - A {# line number}
   - A {# URL} (most commonly to an external resource)
   - A {# detached modifier} followed by the name of the linkable
   -- {# nestable detached modifiers} can:*NOT* be linked to
   - A {# custom detached modifiers}[custom detached modifier] specifically made for links (`/`,
     `#`, `?`, `=`)
   - A {**** Timestamps (`@`)}[timestamp]

*** File Location
    The file location is a construct that allows you to specify the /target file/ into which you
    want to link to. This allows you to *link to targets within other files* or just link to other
    Norg files entirely.

    When standalone, the link syntax will simply point to another `.norg` file relative to the
    current file the link is contained in:

    |example
    {:path/to/other-file:}
    |end

    Note that you do *not* provide the `.norg` extension within the path.
    +name path modifiers
    You may use traditional modifiers in your path, like `/` (in e.g. `/my/file`) to signify the
    root of your file system, `~` (in e.g. `~/Documents/my-file`) to signify the current user's home
    directory, /or/ you can use the [Neorg]-specific `$` (in e.g. `$/my/file`) to signify the _root_
    of the [Neorg] workspace. Since not all Norg files will be used strictly by [Neorg], the
    workspace root can be implementation-specific - for git repos the workspace root could be simply
    the root of the repository, and for other note-taking apps it could simply be the root of the
    directory where all the notes are stored.
    When multiple workspaces are present, the `$name` syntax may be used (e.g. `$notes/my/file`) to
    link to a file from another workspace (in the example case named `notes`). When only a single
    workspace is supported by the application running Neorg or the workspace is not found the user
    should be met with an error.

    A file location may /only/ be accompanied by a {# detached modifier}, {# line number} or {# the
    magic char (`#`)}[the magic char], in which case the links look like so:

    |example
    {:path/to/file:123}
    {:path/to/file:# Location within that file}
    {:path/to/file:** Level 2 heading}
    |end

    `/`, `@` and URLs are not allowed in combination with file locations:

    |example
    {:path:/ file} <- invalid
    {:path:@ timestamp} <- invalid
    {:path:https://my-url} <- also invalid
    |end

*** Line Number
    You can also link to a set line number within the current (or other Norg) file.

    The syntax is as follows:
    |example
    Line 1
    Line 2

    This is a reference to line {2}.
    This is a reference to line {:file:4} in a different file.
    |end

    Disambiguating line numbers and URIs is quite simple - URIs do not begin with digits.

*** URL
    You can define a link to an external resource by simply putting in the URL:

    |example
    {https://github.com/nvim-neorg/neorg}
    |end

    Actions related to schemas like `https://`, `ftp://` etc. (when attempting to open the link) are
    handled by a lower level component running Norg, e.g. [Neorg] or the underlying Operating
    System.

*** Detached Modifier
    Norg allows you to link to any {# Structural Detached Modifiers}[structural] or
    {# Range-able Detached Modifiers}[range-able] detached modifier:

    |example
    * I am a level 1 heading

    Strict link to a level 1 heading:
    {* I am a level 1 heading}
    |end

    The inside of the link location looks just like a detached modifier definition, and that is
    because it pretty much is. You can substitute the `*` char for any other
    {# Structural Detached Modifiers}[structural] or {# Range-able Detached Modifiers}[range-able]
    detached modifier, /except/ "ranged" versions of said modifiers - those are *disallowed* within
    the link syntax. By this we mean that syntax like `{$$ Text}` is _invalid_. To link to a ranged
    definition you would still use `{$ Text}`, there is no reason to make a distinction between a
    ranged and non-ranged detached modifier as both have the same meaning, one just allows more
    content to exist within itself.

*** Custom Detached Modifiers
    Apart from linking to the detached modifiers outlined above, you can also link to a set of
    custom modifiers specifically designed for links. These are the `#` (magic), `/` (file), `@`
    (timestamp), `?` (wiki link) and `=` (extended) linkable locations.

**** The Magic Char (`#`)
     Sometimes you simply want to be lazy, or you want to link to an {# inline linkables}[inline
     linkable] that does not have a dedicated modifier to denote it - in these scenarios you would
     use the magic char: `#`. It links to /any/ item type. The syntax is exactly the same as with
     the other modifiers: `{# My Location}`.

**** The File Linkable (`/`)
     Sometimes you may want to link to an external file that is not a Norg file.
     In that case you may use `{/ /path/to/my/file.txt}` (notice the mandatory space after the `/`
     char, just like with the {# detached modifier}s). Paths are relative to the Norg file that
     contains the link unless started with a `/` to denote your file system root.

     In addition to just providing a path, you may also specify a line number at the end via a colon `:`.
     Example:
     |example
     {/ my-file.txt:123} <- This is a link to `my-file.txt` at line 123
     |end

     As with the {*** file location : # path modifiers}[path modifier] syntax, the file linkable
     also supports special characters like `~` for the user's home directory and the special `$`
     character to denote the root of the current workspace.

**** Timestamps (`@`)
     The syntax for timestamps within links is the same as the syntax used in the
     {**** timestamp extension}.

     Example:
     |example
     Frank's birthday is on {@ 5th May}.
     |end

**** Wiki Links (`?`)
     When building large knowledge bases it's sensible to want to quickly create links between files
     without worrying about the location of said file. The *wiki link* allows you to link to any
     heading in any file in the current workspace. You don't specify any file paths within the link,
     just the title of the heading you want to search for.

     Syntax:
     |example
     Cats are {? mammals}, they make for great {? house pets} too!
     |end

     For developers implementing this behavior: there are no restrictions in which order you parse
     your files to hop between wiki links, as long as the following conditions are met:
     - The current file is the first file that is searched (this allows for `?` to also work as a
       generic catchall link for all heading levels)
     - All files in the current workspace are parsed/enumerated (including subdirectories)

***** Additional Behaviors With `{:file:}`
      The wiki link can also be used with the `{:file:}` to limit the search. It can actually double
      as a "heading catchall" operator as mentioned in the previous section - it will match all
      headings regardless of nesting level in the file provided.

**** Extendable Links (`=`)
     Apart from having links with set behaviors Norg also features an extendable link marked with
     the `=` character. This link has its behaviors governed by {** attached modifier extensions}
     supplied to the link and by the software running the Norg format (e.g. [Neorg]).

     Syntax:
     |example
     +bibliography ./myreferences.bib
     % my_bibliography

     This is a reference to a bibliography: {= Neorg2022}(my_bibliography).
     |end

     For a more detailed explanation of the behavior of this link consult the [semantics document].

*** Inline Linkables
    Although most linkable items are either {# structural detached modifiers}[structural] or
    {# range-able detached modifiers}[range-able], there are also syntax elements in Norg that
    are inline - these are the `#name` {# Carryover Tags}[carryover tag] and the
    {# Inline Link Targets}[inline link target]. Both of these can only be linked to through the
    {# The Magic Char (`#`)}[the magic char].

*** Differences Between File Linkables
    You may have realized that there are many ways to reference a file:
    - `{:my/file:}`
    - `{/ my/file.norg}`
    - `{file://my/file.norg}`

    Why are there this many?
    ~ `{:my/file:}` is strictly to access `.norg` files and nothing else. More specifically, it's
       designed to access a resource /within/ a file (`{:my/file:* Heading}`), with the side effect
       of being able to also exist in a standalone fashion (`{:my/file:}`).
    ~ `{/ my/file.norg}` is used to link to a file and a file /only/ (vs `{:my/file:* Heading}`
       which links to an element within a file). Although it /can/ link to `.norg` files, its main
       use is to link to non-`.norg` files instead. Using the `/` syntax also disallows you from
       accessing items within the file.
    ~ `{file://my/file.norg}` is simply utilizing the `file://` schema to access a file. This
       isn't /the/ recommended way to link to files, but it exists simply because of URI schemas.

*** Scoping
    Within linkables it is possible to narrow down the search of the link via the `| : |` scoping
    modifier. This modifier can exist because under normal circumstances when parsing e.g. the title
    of a heading a `| : |` sequence of characters would be considered an {* intersecting
    modifiers}[intersecting modifier].

    Below is an example of the scoping modifier in use:
    |example
    {* Heading Name : *** Level 3 heading}
    |end

    The search narrows the search to a `Level 3 heading` /within/ a level 1 heading called `Heading
    Name`. This search is descending in terms of nesting, in other words, you /cannot/ do
    `{*** Heading3 : * Heading1}`.

    This scoping is not limited to any item type. You are free to perform searches like
    `{$ Definition : $ Nested Definition : ^ Footnote}`, which searches for a footnote within a
    definition called `Nested Definition` within a definition called `Definition`.

** Link Description
   Link descriptions are denoted by square brackets: `[]`. They contain the description for either a
   {# link location} (by placing the description after the link location or an anchor declaration),
   an {# anchors}[anchor] definition (by placing the description before the link location) or an
   anchor declaration (where the /only/ syntax item *is* the link description). Anchors are
   described {# anchors}[later on].

** Links
   Links in Norg can exist as a standalone {# link location} in which case their text is used as
   the link title (often makes sense for headings):

   |example
   {* I am a standalone link}
   |end

   When a custom description is required, it must be placed *_after_* the link location. This makes
   sense in terms of writing as you first define where you link to, and then annotate it afterwards:

   |example
   Click {* I am a link}[here] to find out more.
   |end

** Anchors
   Norg also has a concept called *anchors*. These allow you to place a standalone
   {** link description} inside of text (referred to as an <anchor declaration>).
   The target which this anchor links to can then be _defined_ at another place in the document
   with an <anchor definition> which is an initial {** link description} followed by a
   {** link location}. This is especially useful when you want to link to the same target very
   often, like for example a specific website.

   Below are a few usage examples:
   |example
   [Neorg] is a fancy organizational tool for everyone.

   I like shilling [Neorg]{https://github.com/nvim-neorg/neorg} sorry :(
   |end
   Here, we /declare/ the anchor once at the top, then /define/ the anchor at the very bottom. The
   `[Neorg]` declaration points directly to the website, just like the definition does. It's like a
   copy + paste of the link location without needing to type it out.

   Other than the declaration behavior described above anchors have no other special meaning and/or
   semantics, and behave just like regular {** links} do. This means they can be used as a
   substitute for regular {** links} should the user prefer the "description + location" syntax
   versus the "location + description" syntax.

   Anchors (like {** links}) may also be described by using `[...]`, in which case the syntax looks
   like this: `[anchor name][anchor description]`.

** Inline Link Targets
   Finally, Norg also has the possibility of placing link targets at arbitrary inline positions in
   your document. We call these {# inline link targets} which are formatted inside angled brackets:
   `<>`.

   |example
   One thing to mention is <inline link targets> - they allow you to link to any location in a
   document.

   ...

   Refer to {# inline link targets} if you are interested in learning more.
   |end

   An important thing to note is that since inline link targets are - well - inline, they cannot be
   directly linked to with a dedicated char in the link syntax. To link to these syntax elements you
   may /only/ use {# the magic char (`#`)}[the magic char].

   Unlike {** links} and {** anchors}, {# inline link targets} may /not/ have a description.

** Valid/Invalid Examples
*** Valid Examples
    |example
    {link}

    {* 
    text}

    {* text }

    {* some
    text   }

    {:link:}

    {:link:20}

    {# link
       text}

    {* a link
    to a heading}

    {* text}[content ]

    {* a
    link to a heading}[with
    a description]

    [te
    xt]{# linkable}

    {* Link to {# headings}[heading]}[*markup*]
    |end

*** Invalid Examples
    |example
    {*text}

    {:file:https://github.com}
    {:file:/ file.txt}
    {:file:@ Wednesday 30th Jan}

    {
    * text}

    {
        * text
    }

    {* text
    }

    { * text}

    {* text}[
        text
    ]

    {* text}[text
    ]

    {* text}[
    text]
    |end

* Standard Library
  Norg comes loaded with a predetermined set of {*** attributes} and {** macro tags} for
  different {* layers} of the syntax. These are defined in the [semantics document].

* Precedence
  Precedence in Norg is rather simple and intuitive.
  - All non-inline elements have direct precedence over all inline elements.
  - Inline elements with a deterministic start and end have greater priority than those that don't.
  - Verbatim elements have greater priority than non-verbatim elements.

  Here's the full list ordered by decreasing precedence:
  ~ {# Tags} (`#infecting`, `+carryover`, `.infirm`, `\|standard`, `@verbatim` and `=macro`)
  ~ {# Structural detached modifiers}
  ~ {# Nestable detached modifiers} and {# range-able detached modifiers} (there is no such case
    where these could overlap)
  ~ {# Detached modifier extensions}
  ~ {# Linkables} (`{}`, `[]`, `<>`)
  ~ Verbatim {# free-form attached modifiers} (`\|``|`, `\|``|`)
  ~ {# Escaping}[The escape character] (`\`)
  ~ Verbatim {# attached modifiers}
  ~ Standard (non-verbatim) {# free-form attached modifiers} (`|**|`, `|//|` etc.)
  ~ Standard (non-verbatim) {# attached modifiers}

  Should any extra precedence problems arise (let us know if you find any) they can be disambiguated
  through a simple left-to-right precedence approach.

  Note that although e.g. linkables are above standard attached modifiers, this does not mean that
  standard attached modifiers cannot /contain/ linkables, but in case there is an overlap the
  linkable will have higher precedence.

  For example, this is valid:
  |example
  *{# i am a bold link!}*
  |end

  However, in this case:
  |example
  *am I {* bold?} - no!
  |end
  The link takes precedence, and no bold is rendered.

* Layers
  Norg is built up of layers, or in other words a set of features that a parser/tool can support
  depending on how much of the specification they'd like to deal with.

  It's recommended to stick to these layers when implementing Norg in your own application (as it's
  easy to tell end users that an application supports e.g. "layer 2" of the Norg specification), but
  of course these can't apply to every possible use case. In such case you can use a /custom layer/
  and pick and choose what you want to support. Just make sure to let your users know which features
  you've implemented, so they don't get confused!

** Layer 1
   The first layers contains a very low level implementation of Norg's markup for use in e.g. a
   messaging application. This includes:
   - {* Attached Modifiers} (excluding variables, inline mathematics and the null detached modifier)
   - {** Links} (only the {*** URL} type)
   - The {*** escaping}[escape sequence char (`\\`)]

** Layer 2
   The second layer outlines the basic structure for a document:
   - {** Nestable Detached Modifiers} (only quotes, lists)
   - {*** Headings}
   - {* Linkables} (broader support for {** links} (minus {**** timestamps (`@`)},
     {**** wiki links (`?`)} and {**** extendable links (`=`)}), {** anchors})
   - {*** Verbatim Ranged Tags} (`@code`, etc.)
   - {** Delimiting Modifiers}

** Layer 3
   This layer is for documents of medium/high complexity:
   - Support for {**** timestamps (`@`)} and {**** wiki links (`?`)} in
     {** links}
   - {** Inline Link Targets}
   - {** Carryover Tags} (`#name`, `#color`/`+name`, `+color` etc.)
   - {** Detached Modifier Extensions}
   - {** Detached Modifier Suffix}
   - {** Range-able Detached Modifiers} (excluding {*** table cells})
   - {** Link Modifier}

** Layer 4
   The fourth layer supports 80% of the most commonly used features for writing high level and
   typeset Norg documents.
   - Support for {**** extendable links (`=`)} and {*** scoping}
   - {*** Standard Ranged Tags} (`\|comment`, etc.)
   - {*** Table cells}
   - {** Free-form Attached Modifiers}
   - {* Intersecting modifiers}
   - {** Attached Modifier Extensions}
   - The inline mathematics (`$$`) and variable (`&&`) {* attached modifiers}

** Layer 5
   Layer five can be seen as the ultimate boss - it features the dynamic elements of Norg
   documents, including macros, variables and parsing of eval blocks.
   - Interpretation/Execution of {*** macro tags}
   - Semantic understanding/execution of all other tag types
   - Evaluation of `@code` blocks for the {:1.0-semantics:* Janet}[Janet] language (if they are marked
     with `#eval`) and full support for the janet standard library.

   ===

%| vim: set tw=100 :|%