WORKPLAN

---+ Concurrent RDF workplan

  * Establish triple-GC						[OK]

  * Establish expansion of triple hash-tables			[OK]

  * Remove old locking code.					[OK]

  * Establish compatible broadcasting				[OK]

  * Duplicate suppression by maintaining a table of duplicate
    answers.							[OK]

  * Deal with subPropertyOf predicate clouds			[OK]

  * Deal with rdf_update/4,5.					[OK]

  * Optimize the following tables in GC (i.e., by cloning older
    objects into new ones):
	- resource-db
	- predicate-db
	- graph-db

  * Concurrent load: not that we are already loading some graph	[UNTESTED]
    and make a concurrent load wait for completion by the other
    thread.

  * Randomized Test framework (test_subprop.pl).

    - Randomly mutating graphs					[OK]
    - Stress testing
      - Run controlled tests concurrently in transactions?	[OK]

  * rdf_gc							[OK]
    - Erased triples that cannot really be deleted because a transaction/snapshot
      blocks this.
      - Nothing will change if oldest generation doesn't change.

  * Reachability matrices
    - Transaction-specific matrices must be invalidated after completion
      of the transaction.
      - Flag them as invalid by setting died to GEN_PREHIST?	[OK]
    - Implement matrix-GC.					[OK]

  * Ordering of literal values should be based on SPARQL literal ordering.

================
Issues
================

  * After loading P6 rewrite: old: 1209415 duplicates, now 8!?

  * Deadlock: lookupAtom() --> GC --> free_node_data() --> PL_unregister_atom()
    Can be fixed using atomic incr/decr for PL_unregister_atom(). [OK (GCC)]