2010-08-12 wenzelm 2010-08-12 clarified "state" (accumulated data) vs. "exec" (execution that produces data); generic type (ML) / Document.ID;
2010-08-11 wenzelm 2010-08-11 represent document ids by (long) int, to benefit from the somewhat faster Inttab in ML (LinearSet in Scala is invariably indexed by native object ids);
2010-08-05 wenzelm 2010-08-05 simplified/refined document model: collection of named nodes, without proper dependencies yet; moved basic type definitions for ids and edits from Isar_Document to Document; removed begin_document/end_document for now -- nodes emerge via edits; edits refer to named nodes explicitly;