Abstract: A system of managing a large number of complex versioned documents. Each document is given a tree structure such as document, chapters, sections and paragraphs. Also, the document is divided into locking units which can be individual nodes, such as one chapter, or subtrees such as one chapter and its three sections. Each locking unit must be checked out by the editing user, at which time it is not available for editing by any other user. Each locking unit contains pointers to the content of its nodes and to a shadow object for each node. The shadow object is allocated in unversioned storage, which does not have to be checked out. The shadow object contains pointers to its corresponding node, to clusters the node belongs to and to the nodes' parent node or nodes. This structure allows a user to reuse parts of a document in another document or include that part in a cluster even when the locking unit containing the part is checked out by another user.