diff --git a/examples/helloworld.yaml b/examples/helloworld.yaml
index 42e2c8cc..34b40e5c 100644
--- a/examples/helloworld.yaml
+++ b/examples/helloworld.yaml
@@ -7,12 +7,9 @@
     - kind: print
       filename: /dev/stdout
   ports:
-    init:
+    begin:
       - name: hello_world
         port: in
-  env:
-    PORT:
-      - data: '{{ .PORT }}'
 
 - kind: step
   name: good_bye
diff --git a/pkg/node/port.go b/pkg/node/port.go
index 48324d88..470996a3 100644
--- a/pkg/node/port.go
+++ b/pkg/node/port.go
@@ -9,14 +9,16 @@ import (
 // Commonly used port names.
 const (
 	PortInit  = "init"
+	PortBegin = "begin"
 	PortTerm  = "term"
+	PortFinal = "final"
 	PortIO    = "io"
 	PortIn    = "in"
 	PortOut   = "out"
 	PortError = "error"
 )
 
-var portExp = regexp.MustCompile(`(\w+)\[(\d+)\]`)
+var subscript = regexp.MustCompile(`(\w+)\[(\d+)\]`)
 
 // PortWithIndex formats the port name as "name[index]".
 func PortWithIndex(name string, index int) string {
@@ -24,16 +26,16 @@ func PortWithIndex(name string, index int) string {
 }
 
 // NameOfPort extracts the base name from a port name formatted as "name[index]".
-func NameOfPort(name string) string {
-	if groups := portExp.FindStringSubmatch(name); groups != nil {
+func NameOfPort(key string) string {
+	if groups := subscript.FindStringSubmatch(key); groups != nil {
 		return groups[1]
 	}
-	return name
+	return key
 }
 
 // IndexOfPort extracts the index from a port name formatted as "name[index]".
-func IndexOfPort(name string) (int, bool) {
-	if groups := portExp.FindStringSubmatch(name); len(groups) == 3 {
+func IndexOfPort(key string) (int, bool) {
+	if groups := subscript.FindStringSubmatch(key); len(groups) == 3 {
 		if index, err := strconv.Atoi(groups[2]); err == nil {
 			return index, true
 		}
diff --git a/pkg/symbol/loader.go b/pkg/symbol/loader.go
index 95464a22..d4ab43f9 100644
--- a/pkg/symbol/loader.go
+++ b/pkg/symbol/loader.go
@@ -3,9 +3,9 @@ package symbol
 import (
 	"context"
 	"errors"
-	"github.com/iancoleman/strcase"
 	"reflect"
 
+	"github.com/iancoleman/strcase"
 	"github.com/siyul-park/uniflow/pkg/resource"
 	"github.com/siyul-park/uniflow/pkg/scheme"
 	"github.com/siyul-park/uniflow/pkg/spec"
diff --git a/pkg/symbol/table.go b/pkg/symbol/table.go
index 2c2622fe..8aa34a8a 100644
--- a/pkg/symbol/table.go
+++ b/pkg/symbol/table.go
@@ -155,7 +155,7 @@ func (t *Table) Keys() []uuid.UUID {
 	t.mu.RLock()
 	defer t.mu.RUnlock()
 
-	var ids []uuid.UUID
+	ids := make([]uuid.UUID, 0, len(t.symbols))
 	for id := range t.symbols {
 		ids = append(ids, id)
 	}
@@ -272,10 +272,13 @@ func (t *Table) load(sb *Symbol) error {
 	linked := t.linked(sb)
 	for _, sb := range linked {
 		if t.active(sb) {
+			if err := t.call(sb, node.PortInit); err != nil {
+				return err
+			}
 			if err := t.loadHooks.Load(sb); err != nil {
 				return err
 			}
-			if err := t.call(sb, node.PortInit); err != nil {
+			if err := t.call(sb, node.PortBegin); err != nil {
 				return err
 			}
 		}
@@ -294,6 +297,9 @@ func (t *Table) unload(sb *Symbol) error {
 			if err := t.unloadHooks.Unload(sb); err != nil {
 				return err
 			}
+			if err := t.call(sb, node.PortFinal); err != nil {
+				return err
+			}
 		}
 	}
 	return nil