diff --git a/objects.go b/objects.go
index 7dc06c6..5ff4f65 100644
--- a/objects.go
+++ b/objects.go
@@ -45,11 +45,21 @@ func VKeyId(key []byte) rdx.ID {
 	return rdx.IDFromBytes(key[1:])
 }
 
+// A class contains a number of fields. Each Field has
+// some RDT type. A class can inherit another class.
+// New fields can be appended to a class, but never removed.
+// Max number of fields is 128, max inheritance depth 32.
+// When stored, a class is an append-only sequence of Ts.
+// The syntax for each T: "XName", where X is the RDT.
+// For the map types, can use "MSS_Name" or similar.
 type Field struct {
-	Name    string
-	RdxType byte
+	Name       string
+	RdxType    byte
+	RdxTypeExt []byte
 }
 
+type Fields []Field
+
 func (f Field) Valid() bool {
 	for _, l := range f.Name { // has unsafe chars
 		if l < ' ' {
@@ -61,8 +71,6 @@ func (f Field) Valid() bool {
 		len(f.Name) > 0 && utf8.ValidString(f.Name))
 }
 
-type Fields []Field
-
 func (f Fields) Find(name string) (ndx int) {
 	for i := 0; i < len(f); i++ {
 		if f[i].Name == name {
diff --git a/rdx/A.go b/rdx/A.go
new file mode 100644
index 0000000..a69a1a4
--- /dev/null
+++ b/rdx/A.go
@@ -0,0 +1,58 @@
+package rdx
+
+import "github.com/drpcorg/chotki/protocol"
+
+// append-only collection of Terms
+type LogT []string
+
+func Amerge(tlvs [][]byte) (merged []byte) {
+	ih := ItHeap[*AIterator]{}
+	for _, tlv := range tlvs {
+		ih.Push(&AIterator{FIRSTIterator{TLV: tlv}})
+	}
+	for ih.Len() > 0 {
+		merged = append(merged, ih.Next()...)
+	}
+	return
+}
+
+func Atlv(log LogT) (tlv []byte) {
+	for n, t := range log {
+		bare := FIRSTtlv(int64(n), 0, []byte(t))
+		tlv = protocol.AppendHeader(tlv, Term, len(bare))
+		tlv = append(tlv, bare...)
+	}
+	return
+}
+
+func AnativeT(tlv []byte) (log LogT) {
+	it := FIRSTIterator{TLV: tlv}
+	for it.Next() {
+		if it.lit != Term {
+			continue
+		}
+		log = append(log, string(it.val))
+	}
+	return
+}
+
+type AIterator struct {
+	FIRSTIterator
+}
+
+func (a *AIterator) Merge(bb SortedIterator) int {
+	b := bb.(*AIterator)
+	if a.revz > b.revz {
+		return MergeBA
+	} else if a.revz < b.revz {
+		return MergeAB
+	}
+	cmp := FIRSTcompare(a.one, b.one)
+	if cmp == 0 {
+		return MergeA
+	} else if cmp < 0 {
+		return MergeAB
+	} else {
+		return MergeBA
+	}
+}
diff --git a/rdx/A_test.go b/rdx/A_test.go
new file mode 100644
index 0000000..e59766c
--- /dev/null
+++ b/rdx/A_test.go
@@ -0,0 +1,30 @@
+package rdx
+
+import (
+	"github.com/drpcorg/chotki/protocol"
+	"github.com/stretchr/testify/assert"
+	"testing"
+)
+
+func TestAmerge(t *testing.T) {
+	tlv := Atlv(LogT{
+		"Ione",
+		"Stwo",
+		"Rthree",
+	})
+	tlv2 := Atlv(LogT{
+		"Ione",
+		"Stwo",
+		"Rthree",
+		"Tfour",
+	})
+	tlv2b := Amerge(protocol.Records{tlv, tlv2})
+	assert.Equal(t, tlv2, tlv2b)
+
+	one := protocol.Record('T', FIRSTtlv(3, 0, []byte("Tfour")))
+	tlv3 := Amerge(protocol.Records{tlv, one})
+	assert.Equal(t, tlv2, tlv3)
+
+	tlv4 := Amerge(protocol.Records{tlv, one, tlv2, tlv3})
+	assert.Equal(t, tlv2, tlv4)
+}