1. An SGML type document managing apparatus for allowing users to create, edit and use an SGML type document collaboratively, comprising: means for automatically creating a partial editing document type definition corresponding to a partial editing request that may cause a partial structure of the document to be changed, the partial editing document type definition being formed by modifying the original document type definition of the entire document so that it represents a restriction against partial editing due to the editing state, which is determined based on the existing document structure and influence of other editing processes executing in parallel at the time when the partial editing request is issued; and means for partially editing the document on the condition that the consistency of the document can be maintained with the partial editing document type definition.