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The Hypertext Abstract Machine (HAM) (Campell and Goodman, 1990) is a general purpose, transaction based, multi user server for a hypertext storage system. The HAM storage model is based in five objects: graphs, contexts, nodes, links and attributes. A graph contains one or more contexts. Contexts partition the data among the graph. Each context has one parent context and zero or more child contexts. A node contains arbitrary data that can be stored as text or binary fields. Versioning of nodes is possible. A cross-context link relates two nodes in different contexts. Attributes can be attached to contexts, nodes or links. HAM provides a filtering mechanism that allows subsets of HAM objects to be extracted from large graphs.