diff --git a/scopes.go b/scopes.go
index 45e9c61..bd46d5a 100644
--- a/scopes.go
+++ b/scopes.go
@@ -8,6 +8,18 @@ import (
 	"sync"
 )
 
+// elementary types
+
+type Ident uint
+
+type Data interface{}
+
+type Map map[string]Data
+type StrMap map[string]string
+
+type Slice []Data
+type StrSlice []string
+
 // services - context
 
 type Services map[string]Context
@@ -30,12 +42,7 @@ type Context interface {
 	Send(Message)
 }
 
-// data (payload), message, address
-
-type Data interface{}
-
-type Map map[string]Data
-type Slice []Data
+// payload, message, address types
 
 type Payload interface {
 	fmt.Stringer
diff --git a/storage/template.go b/storage/template.go
index fe13566..7226647 100644
--- a/storage/template.go
+++ b/storage/template.go
@@ -4,6 +4,7 @@ import (
 	"strings"
 	"text/template"
 
+	lib "git.sr.ht/~cco/go-scopes"
 	"git.sr.ht/~cco/go-scopes/logging/log"
 )
 
@@ -23,7 +24,7 @@ func Template(name, src string) *template.Template {
 	return t
 }
 
-func BuildSql(t *template.Template, data map[string]any) string {
+func BuildSql(t *template.Template, data lib.Map) string {
 	var out strings.Builder
 	err := t.Execute(&out, data)
 	if err != nil {
diff --git a/storage/tracking/tracking.go b/storage/tracking/tracking.go
index 06e1642..06b0724 100644
--- a/storage/tracking/tracking.go
+++ b/storage/tracking/tracking.go
@@ -11,18 +11,36 @@ import (
 	sql "git.sr.ht/~cco/go-scopes/storage"
 )
 
+type Track interface {
+	TrackId() lib.Ident
+}
+
+type BaseTrack = track
+type BaseContainer = container
+
+// basic track implementation
+
 type track struct {
-	trackId   uint
-	head      map[string]string
+	trackId   lib.Ident
+	head      lib.StrMap
 	timeStamp *time.Time
-	data      lib.Data
+	data      lib.Map
 	container *container
 }
 
-func (tr *track) TrackId() uint {
+func SimpleTrack(taskId, userName string, data lib.Map) track {
+	return track{
+		head: lib.StrMap{"taskId": taskId, "userName": userName},
+		data: data,
+	}
+}
+
+func (tr *track) TrackId() lib.Ident {
 	return tr.trackId
 }
 
+// basic container implementation
+
 type container struct {
 	tableName  string
 	headFields []string
@@ -30,13 +48,6 @@ type container struct {
 	storage    *sql.Storage
 }
 
-func SimpleTrack(taskId, userName string, data lib.Map) track {
-	return track{
-		head: map[string]string{"taskId": taskId, "userName": userName},
-		data: data,
-	}
-}
-
 func SimpleContainer(db *sql.Storage) *container {
 	return &container{
 		tableName:  "tracks",
@@ -46,7 +57,7 @@ func SimpleContainer(db *sql.Storage) *container {
 	}
 }
 
-func (cont *container) Insert(tr *track) uint {
+func (cont *container) Insert(tr *track) lib.Ident {
 	var columns []string
 	var values []any
 	for _, k := range cont.headFields {
@@ -57,14 +68,14 @@ func (cont *container) Insert(tr *track) uint {
 	b, _ := json.Marshal(tr.data)
 	values = append(values, b)
 	db := cont.storage
-	data := map[string]interface{}{
+	data := lib.Map{
 		"schema":    db.Schema,
 		"tablename": cont.tableName,
 		"columns":   columns,
 	}
 	sql := storage.BuildSql(SqlInsert, data)
 	if res := storage.QueryCol[uint](db, sql, values...); res != nil {
-		trid := res[0]
+		trid := lib.Ident(res[0])
 		tr.trackId = trid
 		tr.container = cont
 		return trid
@@ -74,7 +85,7 @@ func (cont *container) Insert(tr *track) uint {
 
 func (cont *container) CreateTable() *container {
 	db := cont.storage
-	data := map[string]interface{}{
+	data := lib.Map{
 		"schema":     db.Schema,
 		"tablename":  cont.tableName,
 		"headFields": cont.headFields,
@@ -82,9 +93,7 @@ func (cont *container) CreateTable() *container {
 		"params":     db.Params,
 	}
 	sql := storage.BuildSql(SqlCreate, data)
-	//println(sql)
-	_, err := db.Exec(sql)
-	if err == nil {
+	if _, err := db.Exec(sql); err == nil {
 		return cont
 	}
 	return nil
diff --git a/tests/storage_test.go b/tests/storage_test.go
index 2f1922a..453bf6c 100644
--- a/tests/storage_test.go
+++ b/tests/storage_test.go
@@ -70,7 +70,7 @@ func TrackingTest(t *testing.T, cfg *sql.Cfg, db *sql.Storage) {
 	cont.CreateTable()
 	track := tracking.SimpleTrack("t01", "john", lib.Map{})
 	cont.Insert(&track)
-	t.AssertEqual(track.TrackId(), uint(1))
+	t.AssertEqual(track.TrackId(), lib.Ident(1))
 }
 
 func MessageTest(t *testing.T, cfg *sql.Cfg, db *sql.Storage) {