diff --git a/core/coreiface/interface.go b/core/coreiface/interface.go
index 3e0e3d460..9dca7f3c9 100644
--- a/core/coreiface/interface.go
+++ b/core/coreiface/interface.go
@@ -219,6 +219,14 @@ type ObjectAPI interface {
 	// * "json"
 	WithInputEnc(e string) options.ObjectPutOption
 
+	// WithDataType specifies the encoding of data field when using Josn or XML
+	// input encoding.
+	//
+	// Supported types:
+	// * "text" (default)
+	// * "base64"
+	WithDataType(t string) options.ObjectPutOption
+
 	// Get returns the node for the path
 	Get(context.Context, Path) (Node, error)
 
@@ -234,20 +242,20 @@ type ObjectAPI interface {
 	// AddLink adds a link under the specified path. child path can point to a
 	// subdirectory within the patent which must be present (can be overridden
 	// with WithCreate option).
-	AddLink(ctx context.Context, base Path, name string, child Path, opts ...options.ObjectAddLinkOption) (Node, error)
+	AddLink(ctx context.Context, base Path, name string, child Path, opts ...options.ObjectAddLinkOption) (Path, error)
 
 	// WithCreate is an option for AddLink which specifies whether create required
 	// directories for the child
 	WithCreate(create bool) options.ObjectAddLinkOption
 
 	// RmLink removes a link from the node
-	RmLink(ctx context.Context, base Path, link string) (Node, error)
+	RmLink(ctx context.Context, base Path, link string) (Path, error)
 
 	// AppendData appends data to the node
-	AppendData(context.Context, Path, io.Reader) (Node, error)
+	AppendData(context.Context, Path, io.Reader) (Path, error)
 
 	// SetData sets the data contained in the node
-	SetData(context.Context, Path, io.Reader) (Node, error)
+	SetData(context.Context, Path, io.Reader) (Path, error)
 }
 
 // ObjectStat provides information about dag nodes
@@ -267,7 +275,7 @@ type ObjectStat struct {
 	// DataSize is the size of data block section
 	DataSize int
 
-	// CumulativeSize is size of node
+	// CumulativeSize is size of the tree (BlockSize + link sizes)
 	CumulativeSize int
 }
 
diff --git a/core/coreiface/options/object.go b/core/coreiface/options/object.go
index fe86a1cde..9c8c9a9dd 100644
--- a/core/coreiface/options/object.go
+++ b/core/coreiface/options/object.go
@@ -6,6 +6,7 @@ type ObjectNewSettings struct {
 
 type ObjectPutSettings struct {
 	InputEnc string
+	DataType string
 }
 
 type ObjectAddLinkSettings struct {
@@ -33,6 +34,7 @@ func ObjectNewOptions(opts ...ObjectNewOption) (*ObjectNewSettings, error) {
 func ObjectPutOptions(opts ...ObjectPutOption) (*ObjectPutSettings, error) {
 	options := &ObjectPutSettings{
 		InputEnc: "json",
+		DataType: "text",
 	}
 
 	for _, opt := range opts {
@@ -74,6 +76,13 @@ func (api *ObjectOptions) WithInputEnc(e string) ObjectPutOption {
 	}
 }
 
+func (api *ObjectOptions) WithDataType(t string) ObjectPutOption {
+	return func(settings *ObjectPutSettings) error {
+		settings.DataType = t
+		return nil
+	}
+}
+
 func (api *ObjectOptions) WithCreate(create bool) ObjectAddLinkOption {
 	return func(settings *ObjectAddLinkSettings) error {
 		settings.Create = create