DES 1.6.2 Released

[fernan]

[Apologies for multiple receptions]

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

  Datalog Educational System version 1.6.2
  http://des.sourceforge.net

has been launched on March, 10th, 2009 and ported to 

  GNU Prolog 1.3.1

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 1.6.2 of DES adds to previous version (1.6.1):

Enhancements:
        o       Null values has been included both for Datalog programs and SQL 
statements
        o       Novel outer join Datalog functions: lj/3, rj/3, and fj/3
        o       Outer join SQL clauses added: LEFT [OUTER] JOIN, RIGHT [OUTER] 
JOIN, and FULL [OUTER] JOIN
        o       Solving algorithm enhanced for stratified queries. Partial 
recomputations of lower-stratum predicates are avoided
        o       Compilation of SQL WHERE conditions to Datalog rules now 
provides shorter and more efficient programs
        o       Disjunctions in Datalog rule bodies
        o       New commands:
                -       /development Switch Enables/Disables development 
listings. These listings show the source-to-source translations needed to 
handle null values, Datalog outer join built-ins, and disjunctive literals
                -       /development Displays whether development listings are 
enabled
                -       /simplification Switch Enables/Disables simplification 
of Datalog rules. Rules with equalities, true, and not(BooleanValue) are 
simplified
                -       /simplification Displays whether rule simplification is 
enabled
        o       WHERE conditions accept arithmetic expressions (e.g., 1+t.a>3)
        o       Display of the number of undefined computed tuples, and the 
number of tuples in the extension table answer and call sets
        o       Parentheses in Datalog rule bodies, not only in arithmetic 
expressions, are allowed
        o       Parentheresed listings of Datalog rule bodies, making more 
readable bodies with conjunctions and disjunctions
        o       Simplification of rules containing equalities
Changes:
        o       Rule listings are grouped by predicate name and arity. For a 
given predicate name and arity, facts come first, followed by rules with right 
hand sides. The order of facts and rules follows Prolog standard order between 
terms
        o       Datalog rules resulting from translating views change the 
naming convention to (the more readable) ViewName_Arity_Number in lieu of 
ViewName$pNumber
        o       Results from Datalog autoviews are given the relation name 
answer instead of autoview
        o       Pretty-print is applied to all Datalog rule listings
        o       Safety warnings are not hidden by computability warnings
Fixed bugs:
        o       Unformatted SQL statement display for certain conditions and 
joins
        o       Parsing error for EXISTS clause (no blanks between EXISTS and 
opening parenthesis were allowed)
        o       SQL arithmetic functions could only be written in lowercase
        o       Some WHERE conditions incorrectly translated into Datalog 
conditions (bug introduced in version 1.6.1)
        o       Some WHERE conditions involving parentheses incorrectly parsed
        o       Correlated SQL queries with non-basic conditions were 
incorrectly translated into Datalog rules
        o       DELETE SQL statements failed to be parsed (copy-paste bug 
introduced in version 1.6.1)
        o       Some unsafe Datalog queries were not rejected for computation 
(as X=Y)
        o       During startup batch processing of des.ini, some tasks upon 
exceptions were not performed
        o       Typing des. in a Prolog interpreter after abnormally quitting 
the system did not result in exception catching anymore
        o       A class of unsafe rules was not be able to be preprocessed for 
reordering body goals, yielding non-termination
        o       Incomplete error message
Known bugs:
        o       The projection list of a natural outer join is not correct in 
all cases
Caveat:
        o       Computable SQL statements follow the grammar in the manual. The 
current grammar parses extra clauses which cannot be computed yet (e.g., GROUP 
BY, ORDER BY, ...)