**** SECONDO Release Notes ****


2007-06-24 Notes on Release 3.0
===============================================================================

Secondo has been improved significantly since version 2.9. Mayor points are the
improved compatibility with different platforms, increased stability, and
increased performance.

Although we did our best to improve general system stability, there are still
some problems with numeric stability, especially in the spatial and
spatiotemporal algebras.

Changes in detail:

 * The Flob concept has been totally re-implemented to avoid the nasty errors
   created by the old Flob-Cache.

 * Several changes have been done to make the SMI code compatible with
   different versions of 3rd party software, namely BerkeleyDB, thus increasing
   compatibility with different platforms.

 * On some platforms, newer library versions miss to include certain header
   files. These are now included explicitly.

 * Many bugfixes regarding system stability: Memory holes have been fixed,
   some operator implementations corrected.

 * For spatial and spatiotemporal datatypes with set semantics, we now
   differentiate between EMPTY and UNDEFINED values.

 * New support structure "TupleFile": This type can be used by algorithms
   that need to materialize data. Data is stored in flat files rather than
   in temporal relations. Also, only data not fitting into the main memory
   buffer gets materialized on harddisc. Should be used as an replacement for
   the "TupleBuffer".

 * Changed implementations/ New algebra: The ExtRelation-2Algebra provides
   external Algorithms for sorting and different join algorithms. Also,
   sorting is now done by a paramerizable multi-stage mergesort, with restricted
   amount of main memory. The new algorithms use TupleFiles instead of
   TupleBuffers.
   Most according original algorithms from the ExtRelationAlgebra have been
   replaced by the operators from this new algebra.

 * New operators in the RTreeAlgebra allow for query-based inspection of the
   tree structures.

 * New modules: The BTree2Algebra provides parametrizable BTrees. The
   RTreeViewer allows for visualized online-exploration of Rtree objects.

 * Optimizer: Exception handling was extended so that now most errors can be
   caught and reported to the user.
   Scripts for executing the BerlinMOD/R benchmark from the optimizer have
   been added to the Optimizer directory.