DES 1.6.1 Released

[Apologies for multiple receptions]

Hello.
This is a mail just for informing that the new release

  Datalog Educational System version 1.6.1
  http://des.sourceforge.net

has been launched on November, 10th, 2008 and ported to 

  GNU Prolog 1.3.0

Release notes are attached to the end of this message.
Please, see http://des.sourceforge.net for details.

  Best regards.

==============================================================
Fernando Sáenz Pérez
Profesor Titular de Universidad / Associate Professor
Home Page: http://www.fdi.ucm.es/profesor/fernan
Tel: + 34 913947642. Fax: + 34 913947547
Despacho / Office: 435 (4ª planta / 4th floor)
Dept. Ingeniería del Software e Inteligencia Artificial / 
Department of Software Engineering and Artificial Intelligence
Universidad Complutense de Madrid
Facultad de Informática
C/Profesor José García Santesmases, s/n
E - 28040 Madrid. Spain
==============================================================



Version 1.6.1 of DES adds to previous version (1.6.0):

Enhancements: 
    o    Arithmetic expressions are allowed in the projection list of SELECT statements
    o    Subqueries in comparisons (=, <, >, ...), in either side or even in both sides of the comparison operator (read as ANY, not ALL, which is unsupported up to now)
    o    Display of the number of computed, inserted and deleted tuples
    o    Commands are case-insensitive
    o    Some tweaks on the SQL parsing code for making it hopefully more understandable and efficient
    o    The answer to a SQL query is a relation with name 'answer', and its schema is displayed when solving it
    o    A new use for the /dbschema command: Now, it accepts an optional argument (a database object, which can be a view or a table name) for restricting the displayed schema 
    o    The /dbschema command informs about local view definitions for each view
    o    A new SQL DDL statement: drop database, which drops the database (including tables, views, and rules)
    o    Stratifications are not computed during building a view that involves local views. As a consequence, several messages are suppressed (as ‘undefined’ and ‘non stratifiable’)

Changes: 
    o    Inserted and deleted tuples are not shown 

Fixed bugs: 
    o    Complex left-hand-side relations in joins failed to be parsed
    o    Conjunctive Prolog goals failed to be parsed (bug introduced in version 1.6.0)
    o    Natural joins now return common attributes only once
    o    Datalog rules involving expressions with (prefix) unary operators were incorrectly displayed as infix
    o    Parsing of Datalog bodies failed is some situations were arithmetic operators were involved (as in /assert p(X) :- X is –(1) )
    o    Parsing of projection lists failed in some situations where table.* was intermixed with references to single table attributes
    o    Program transformation for obtaining safe rules yielded incorrect results in some cases
    o    When dropping a view, its local view definitions (if any) were not dropped as well
    o    Different views could define the same local view name
    o    /listing Name failed to list rules of different arities (bug introduced in version 1.6.0)