The Snapshot must be indexed before the Node is applied; otherwise the Node is stashed. The Snapshot's schema must be the schema of the node's Kind, or extend it. Two concurrent snapshot targets are both heads of the resource; the kind's schema may define a merge, otherwise the client shows both and the next Snapshot lists both in prev. A snapshot target concurrent with a heads target is treated as a head of the Change graph.

Comments, contacts and profiles are snapshot blobs in all but name: each edit is a new blob that replaces the whole value, found by TSID or by key. Stem makes the pattern explicit and gives every such record a node, so it has a parent, an audience and links like a document.