diff --git a/examples/GraphDef-model/model/graphdef.pb b/examples/GraphDef-model/model/model.graphdef
similarity index 100%
rename from examples/GraphDef-model/model/graphdef.pb
rename to examples/GraphDef-model/model/model.graphdef
diff --git a/pkg/model/format.go b/pkg/model/format.go
index 2aba3617..554fb14e 100644
--- a/pkg/model/format.go
+++ b/pkg/model/format.go
@@ -6,6 +6,7 @@ import (
 	"io/ioutil"
 	"os"
 	"path"
+	"strings"
 )
 
 // Format is the definition of model format.
@@ -77,48 +78,55 @@ func (f Format) ValidateDirectory(rootPath string) error {
 	return nil
 }
 
+func ValidateError(modelPath string, modelName string, modelNum int32) error {
+	if modelNum != 1 {
+		return fmt.Errorf("Expected one %v file in %v directory, but found %v .", modelName, modelPath, modelNum)
+	}
+	return nil
+}
+
 func (f Format) validateForSavedModel(modelPath string, files []os.FileInfo) error {
-	var pbFileFlag bool
-	var variablesDirFlag bool
+	var pbFileNum int32
+	var variablesDirNum int32
 	for _, file := range files {
-		if path.Ext(file.Name()) == ".pb" {
-			pbFileFlag = true
+		if file.Name() == "saved_model.pb" {
+			pbFileNum++
 		}
 		if file.IsDir() && file.Name() == "variables" {
-			variablesDirFlag = true
+			variablesDirNum++
 		}
 	}
-	if !pbFileFlag {
-		return fmt.Errorf("there are no *.pb file in %v directory", modelPath)
+	if e := ValidateError(modelPath, "saved_model.pb", pbFileNum); e != nil {
+		return e
 	}
-	if !variablesDirFlag {
-		return fmt.Errorf("there are no variables dir in %v directory", modelPath)
+	if e := ValidateError(modelPath, "variables", variablesDirNum); e != nil {
+		return e
 	}
 	return nil
 }
 
 func (f Format) validateForONNX(modelPath string, files []os.FileInfo) error {
-	var onnxFileFlag bool
+	var onnxFileNum int32
 	for _, file := range files {
 		if path.Ext(file.Name()) == ".onnx" {
-			onnxFileFlag = true
+			onnxFileNum++
 		}
 	}
-	if !onnxFileFlag {
-		return fmt.Errorf("there are no *.onnx file in %v directory", modelPath)
+	if e := ValidateError(modelPath, "*.onnx", onnxFileNum); e != nil {
+		return e
 	}
 	return nil
 }
 
 func (f Format) validateForH5(modelPath string, files []os.FileInfo) error {
-	var h5FileFlag bool
+	var h5FileNum int32
 	for _, file := range files {
 		if path.Ext(file.Name()) == ".h5" {
-			h5FileFlag = true
+			h5FileNum++
 		}
 	}
-	if !h5FileFlag {
-		return fmt.Errorf("there are no *.h5 file in %v directory", modelPath)
+	if e := ValidateError(modelPath, "*.h5", h5FileNum); e != nil {
+		return e
 	}
 	return nil
 }
@@ -135,141 +143,140 @@ func (f Format) validateForPMML(modelPath string, files []os.FileInfo) error {
 }
 
 func (f Format) validateForCaffeModel(modelPath string, files []os.FileInfo) error {
-	var caffeModelFileFlag bool
-	var prototxtFileFlag bool
+	var caffeModelFileNum int32
+	var prototxtFileNum int32
 	for _, file := range files {
 		if path.Ext(file.Name()) == ".caffemodel" {
-			caffeModelFileFlag = true
+			caffeModelFileNum++
 		}
 		if path.Ext(file.Name()) == ".prototxt" {
-			prototxtFileFlag = true
+			prototxtFileNum++
 		}
 	}
-	if !caffeModelFileFlag {
-		return fmt.Errorf("there are no *.caffemodel file in %v directory", modelPath)
+	if e := ValidateError(modelPath, "*.caffemodel", caffeModelFileNum); e != nil {
+		return e
 	}
-	if !prototxtFileFlag {
-		return fmt.Errorf("there are no *.prototxt file in %v directory", modelPath)
+	if e := ValidateError(modelPath, "*.prototxt", prototxtFileNum); e != nil {
+		return e
 	}
 	return nil
 }
 
 func (f Format) validateForNetDef(modelPath string, files []os.FileInfo) error {
-	var initFileFlag bool
-	var predictFileFlag bool
+	var initFileNum int32
+	var predictFileNum int32
 	for _, file := range files {
 		if file.Name() == "init_net.pb" {
-			initFileFlag = true
+			initFileNum++
 		}
 		if file.Name() == "predict_net.pb" {
-			predictFileFlag = true
+			predictFileNum++
 		}
 	}
-	if !initFileFlag {
-		return fmt.Errorf("there are no init_net.pb file in %v directory", modelPath)
+	if e := ValidateError(modelPath, "init_net.pb", initFileNum); e != nil {
+		return e
 	}
-	if !predictFileFlag {
-		return fmt.Errorf("there are no predict_net.pb file in %v directory", modelPath)
+	if e := ValidateError(modelPath, "predict_net.pb", predictFileNum); e != nil {
+		return e
 	}
 	return nil
 }
 
 func (f Format) validateForMXNETParams(modelPath string, files []os.FileInfo) error {
-	var jsonFileFlag bool
-	var paramsFileFlag bool
+	var jsonFileNum int32
+	var paramsFileNum int32
 	for _, file := range files {
-		if path.Ext(file.Name()) == ".json" {
-			jsonFileFlag = true
+		if strings.HasSuffix(file.Name(), "symbol.json") {
+			jsonFileNum++
 		}
 		if path.Ext(file.Name()) == ".params" {
-			paramsFileFlag = true
+			paramsFileNum++
 		}
 	}
-	if !jsonFileFlag {
-		return fmt.Errorf("there are no *.json file in %v directory", modelPath)
+	if e := ValidateError(modelPath, "*symbol.json", jsonFileNum); e != nil {
+		return e
 	}
-	if !paramsFileFlag {
-		return fmt.Errorf("there are no *.params file in %v directory", modelPath)
+	if e := ValidateError(modelPath, "*.params", paramsFileNum); e != nil {
+		return e
 	}
 	return nil
 }
 
 func (f Format) validateForTorchScript(modelPath string, files []os.FileInfo) error {
-	var ptFileFlag bool
+	var ptFileNum int32
 	for _, file := range files {
 		if path.Ext(file.Name()) == ".pt" {
-			ptFileFlag = true
+			ptFileNum++
 		}
 	}
-	if !ptFileFlag {
-		return fmt.Errorf("there are no *.pt file in %v directory", modelPath)
+	if e := ValidateError(modelPath, "*.pt", ptFileNum); e != nil {
+		return e
 	}
 	return nil
 }
 
 func (f Format) validateForGraphDef(modelPath string, files []os.FileInfo) error {
-	var pbFileFlag bool
+	var graphdefFileNum int32
 	for _, file := range files {
-		if path.Ext(file.Name()) == ".pb" {
-			pbFileFlag = true
-			break
+		if path.Ext(file.Name()) == ".graphdef" {
+			graphdefFileNum++
 		}
 	}
-	if !pbFileFlag {
-		return fmt.Errorf("there are no *.pb file in %v directory", modelPath)
+	if e := ValidateError(modelPath, "*.graphdef", graphdefFileNum); e != nil {
+		return e
 	}
 	return nil
 }
 
 func (f Format) validateForTensorRT(modelPath string, files []os.FileInfo) error {
-	var tensorrtFileFlag bool
+	var tensorrtFileNum int32
 	for _, file := range files {
-		if path.Ext(file.Name()) == ".plan" {
-			tensorrtFileFlag = true
+		if path.Ext(file.Name()) == ".plan" || path.Ext(file.Name()) == ".engine" {
+			tensorrtFileNum++
 		}
 	}
-	if !tensorrtFileFlag {
-		return fmt.Errorf("there are no *.plan file in %v directory", modelPath)
+	if e := ValidateError(modelPath, "*.plan or *.engine", tensorrtFileNum); e != nil {
+		return e
 	}
 	return nil
 }
 
 func (f Format) validateForSKLearn(modelPath string, files []os.FileInfo) error {
-	var sklearnFileFlag bool
+	var sklearnFileNum int32
 	for _, file := range files {
 		if path.Ext(file.Name()) == ".joblib" {
-			sklearnFileFlag = true
+			sklearnFileNum++
 		}
 	}
-	if !sklearnFileFlag {
-		return fmt.Errorf("there are no *.joblib file in %v directory", modelPath)
+	if e := ValidateError(modelPath, "*.joblib", sklearnFileNum); e != nil {
+		return e
 	}
 	return nil
 }
 
 func (f Format) validateForXGBoost(modelPath string, files []os.FileInfo) error {
-	var xgboostFileFlag bool
+	var xgboostFileNum int32
 	for _, file := range files {
 		if path.Ext(file.Name()) == ".xgboost" {
-			xgboostFileFlag = true
+			xgboostFileNum++
 		}
 	}
-	if !xgboostFileFlag {
-		return fmt.Errorf("there are no *.xgboost file in %v directory", modelPath)
+	if e := ValidateError(modelPath, "*.xgboost", xgboostFileNum); e != nil {
+		return e
 	}
 	return nil
 }
 
 func (f Format) validateForMLflow(modelPath string, files []os.FileInfo) error {
-	var isMLflowFile bool
+	var MLflowFileNum int32
 	for _, file := range files {
 		if file.Name() == "MLmodel" {
 			// assuming that user would not fool the tool
-			isMLflowFile = true
+			MLflowFileNum++
 		}
 	}
-	if !isMLflowFile {
-		return fmt.Errorf("there are no MLmodel file in %v, directory", modelPath)
+	if e := ValidateError(modelPath, "MLmodel", MLflowFileNum); e != nil {
+		return e
 	}
 	return nil
 }