One has to decide on the unit of data to be locked. There is a specific problem which all distributed hypertext systems have had to tackle, in linking to living documents . Annotation Annotation is the linking of a new commentary node to someone else's existing node. It is the essence of a collaborative hypertext. Protection Protection against unauthorized reading and writing is provided by servers.
Life is simple if the domain is the database, or all the data administered by a given server.
One can also add author-based protection to the contents of a node, or links, which have author information stored about them. There is a problem illustrated by the following example. One might want to make a private annotation to something which is visible world-wide but unwritable. This is a general problem of links being in a different domain to nodes. A possible solution to this is to have, in the private domain, a partial copy of the public web, so that link information can be added to it.