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Schema Viewer maintains a list of recently opened workspace documents in the Recent Workspaces item of the File menu. To open a recently-accessed workspace document, select the Recent Workspaces item in the File menu. A sub-menu will appear listing the four most recently opened workspace documents. If the workspace you wish to open is on the list, select it. (You can change the number of entries in the recent-file list---see hte Customising Schema Viewer section.)