diff --git a/backend/global/file.go b/backend/global/file.go
index 957f3fd..ed437dc 100644
--- a/backend/global/file.go
+++ b/backend/global/file.go
@@ -26,6 +26,17 @@ func (pt PaperType) AB() byte {
 	}
 }
 
+func (pt PaperType) SetAB(x byte) PaperType {
+	n := PaperType(0)
+	switch x {
+	case 'A':
+		n = 1
+	case 'B':
+		n = 2
+	}
+	return pt | n
+}
+
 // MiddleFinal default 平时
 func (pt PaperType) MiddleFinal() string {
 	switch (pt & 0xf0) >> 4 {
@@ -38,6 +49,17 @@ func (pt PaperType) MiddleFinal() string {
 	}
 }
 
+func (pt PaperType) SetMiddleFinal(x string) PaperType {
+	n := PaperType(0)
+	switch x {
+	case "期中":
+		n = 1 << 4
+	case "期末":
+		n = 2 << 4
+	}
+	return pt | n
+}
+
 // FirstSecond default is 年度
 func (pt PaperType) FirstSecond() string {
 	switch (pt & 0x0f00) >> 8 {
@@ -50,6 +72,17 @@ func (pt PaperType) FirstSecond() string {
 	}
 }
 
+func (pt PaperType) SetFirstSecond(x string) PaperType {
+	n := PaperType(0)
+	switch x {
+	case "第1学期":
+		n = 1 << 8
+	case "第2学期":
+		n = 2 << 8
+	}
+	return pt | n
+}
+
 // OpenClose default 闭卷
 func (pt PaperType) OpenClose() string {
 	switch (pt & 0xf000) >> 12 {
@@ -64,6 +97,19 @@ func (pt PaperType) OpenClose() string {
 	}
 }
 
+func (pt PaperType) SetOpenClose(x string) PaperType {
+	n := PaperType(0)
+	switch x {
+	case "开卷":
+		n = 1 << 12
+	case "一页纸开卷":
+		n = 2 << 12
+	case "闭卷":
+		n = 3 << 12
+	}
+	return pt | n
+}
+
 // StudyYear 学年
 type StudyYear uint16
 
@@ -82,6 +128,10 @@ func init() {
 	if err != nil {
 		panic(err)
 	}
+	err = FileDB.db.Create(FileTableQuestion, &Question{})
+	if err != nil {
+		panic(err)
+	}
 	err = FileDB.db.Close()
 	if err != nil {
 		panic(err)
@@ -114,6 +164,7 @@ func (f *FileDatabase) AddFile() {}
 type QuestionJSON struct {
 	Name   string         `json:"name"`   // Name is name or Question ID
 	Points int            `json:"points"` // Points is sum of subs' points or self
+	Rate   float64        `json:"rate"`   // Rate is the avg(non-leaf) or max(leaf) similarity
 	Sub    []QuestionJSON `json:"sub,omitempty"`
 }
 
@@ -122,12 +173,13 @@ type Question struct {
 	Plain  string // Plain is the plain text of the question (like markdown format)
 	XML    []byte // XML is the OpenXML bytes of the question
 	Images []byte // Images is json of the image paths in XML, ex. ['md5.jpg', 'md5.png', ...]
+	Vector []byte // Vector is json of {word: rate, ...} freq
 	Dup    []byte // Dup is json of Duplication struct
 }
 
 // Duplication is the struct representation of Question.Dup
 type Duplication struct {
 	ID   string        `json:"id"`   // ID is hex string for json's 53 bits number
-	Rate float64       `json:"rate"` // Rate is the 重复率 or 总重复率
+	Rate float64       `json:"rate"` // Rate is the avg(non-leaf) or max(leaf) similarity
 	To   []Duplication `json:"to,omitempty"`
 }
diff --git a/backend/utils/cosimi.go b/backend/utils/cosimi.go
new file mode 100644
index 0000000..41637f2
--- /dev/null
+++ b/backend/utils/cosimi.go
@@ -0,0 +1,19 @@
+// edit from https://github.com/kabychow/go-cosinesimilarity
+
+package utils
+
+import "math"
+
+// Similarity len(x) must eq len(y)
+func Similarity(x, y []uint8) float64 {
+	var sum, s1, s2 uint64
+	for i := 0; i < len(x); i++ {
+		sum += uint64(x[i]) * uint64(y[i])
+		s1 += uint64(x[i]) * uint64(x[i])
+		s2 += uint64(y[i]) * uint64(y[i])
+	}
+	if s1 == 0 || s2 == 0 {
+		return 0.0
+	}
+	return float64(sum) / (math.Sqrt(float64(s1)) * math.Sqrt(float64(s2)))
+}
diff --git a/backend/utils/cosimi_test.go b/backend/utils/cosimi_test.go
new file mode 100644
index 0000000..4e2e970
--- /dev/null
+++ b/backend/utils/cosimi_test.go
@@ -0,0 +1,19 @@
+package utils
+
+import (
+	"math"
+	"testing"
+)
+
+func TestSimilarity(t *testing.T) {
+	r := Similarity([]uint8{1, 2, 3}, []uint8{1, 3, 4})
+	t.Log(r)
+	if math.Abs(r-0.9958705948858224) > 1e-6 {
+		t.Fail()
+	}
+	r = Similarity([]uint8{3, 2, 1}, []uint8{1, 3, 4})
+	t.Log(r)
+	if math.Abs(r-0.6813851438692469) > 1e-6 {
+		t.Fail()
+	}
+}