diff --git a/interfaces.go b/interfaces.go
index 8af60fc..65c5356 100644
--- a/interfaces.go
+++ b/interfaces.go
@@ -7,21 +7,23 @@ import (
 
 // DID is a decoded (i.e. from a string) Decentralized Identifier.
 type DID interface {
+	// Method returns the name of the DID method (e.g. "key" for did:key).
 	Method() string
 
-	// TODO: below might be only for DID URLs, is it relevant here?
-	Path() string
-	Query() url.Values
-	Fragment() string
-
+	// Document resolves the DID into a DID Document usable for e.g. signature check.
+	// This can be simply expanding the DID into a Document, or involve external resolution.
 	Document() (Document, error)
-	String() string // return the full DID URL, with path, query, fragment
 
-	// ResolutionIsExpensive returns true if resolving to a Document is an expensive operation, e.g. requiring
-	// an external HTTP request. By contrast, a self-contained DID (e.g. did:key) can be resolved cheaply without
-	// an external call. This can be an indication whether to cache the resolved state.
+	// String returns the string representation of the DID.
+	String() string
+
+	// ResolutionIsExpensive returns true if resolving to a Document is an expensive operation,
+	// e.g. requiring an external HTTP request. By contrast, a self-contained DID (e.g. did:key)
+	// can be resolved cheaply without an external call.
+	// This can be an indication whether to cache the resolved state.
 	ResolutionIsExpensive() bool
 
+	// Equal returns true if this and the given DID are the same.
 	Equal(DID) bool
 }
 
@@ -29,6 +31,9 @@ type DID interface {
 type Document interface {
 	json.Marshaler
 
+	// Context is the set of JSON-LD context documents.
+	Context() []string
+
 	// ID is the identifier of the Document, which is the DID itself.
 	ID() DID
 
@@ -36,7 +41,7 @@ type Document interface {
 	Controllers() []DID
 
 	// AlsoKnownAs returns an optional set of URL describing ???TODO
-	AlsoKnownAs() []url.URL
+	AlsoKnownAs() []*url.URL
 
 	// VerificationMethods returns all the VerificationMethod known in the document.
 	VerificationMethods() map[string]VerificationMethod
diff --git a/methods/did-key/document.go b/methods/did-key/document.go
index b86b6e4..7984a6e 100644
--- a/methods/did-key/document.go
+++ b/methods/did-key/document.go
@@ -32,11 +32,7 @@ func (d document) MarshalJSON() ([]byte, error) {
 		CapabilityInvocation []string                 `json:"capabilityInvocation,omitempty"`
 		CapabilityDelegation []string                 `json:"capabilityDelegation,omitempty"`
 	}{
-		Context: stringSet(
-			did.JsonLdContext,
-			d.signature.JsonLdContext(),
-			d.keyAgreement.JsonLdContext(),
-		),
+		Context:              d.Context(),
 		ID:                   d.id.String(),
 		AlsoKnownAs:          nil,
 		VerificationMethod:   []did.VerificationMethod{d.signature},
@@ -48,6 +44,14 @@ func (d document) MarshalJSON() ([]byte, error) {
 	})
 }
 
+func (d document) Context() []string {
+	return stringSet(
+		did.JsonLdContext,
+		d.signature.JsonLdContext(),
+		d.keyAgreement.JsonLdContext(),
+	)
+}
+
 func (d document) ID() did.DID {
 	return d.id
 }
@@ -57,7 +61,7 @@ func (d document) Controllers() []did.DID {
 	return nil
 }
 
-func (d document) AlsoKnownAs() []url.URL {
+func (d document) AlsoKnownAs() []*url.URL {
 	return nil
 }
 
diff --git a/methods/did-key/key.go b/methods/did-key/key.go
index ddf5744..37db891 100644
--- a/methods/did-key/key.go
+++ b/methods/did-key/key.go
@@ -3,7 +3,6 @@ package didkey
 import (
 	"crypto"
 	"fmt"
-	"net/url"
 	"strings"
 
 	mbase "github.com/multiformats/go-multibase"
@@ -104,18 +103,6 @@ func (d DidKey) Method() string {
 	return "key"
 }
 
-func (d DidKey) Path() string {
-	return ""
-}
-
-func (d DidKey) Query() url.Values {
-	return nil
-}
-
-func (d DidKey) Fragment() string {
-	return ""
-}
-
 func (d DidKey) Document() (did.Document, error) {
 	return document{
 		id:           d,