DES 2.3 Released

[fernan]

[Apologies for multiple receptions]

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

  Datalog Educational System version 2.3 
  http://des.sourceforge.net

has been launched on May, 24th, 2011, and ported to

  GNU Prolog 1.3.1

There have been several improvements in this release, and the major 
feature is a SQL declarative debugger. Users can debug SQL 
views from a declarative debugging point-of-view. The system 
interactively asks questions to the user about relations involved in 
the computation of the debugged view. In addition, trusted 
specifications add semantic references are allowed to cut the number 
of questions down. Another useful feature is the new built-in 
predicate distinct/1 for discarding duplicates from a multiset answer 
when duplicates are enabled. In turn, this allows to support DISTINCT 
and ALL clauses in SQL statements. Moreover, although not directly 
related to that built-in, Datalog aggregate function and predicates 
involving distinct computations are provided: count_distinct, 
avg_distinct, sum_distinct, and times_distinct. As well, SQL 
statements can use the DISTINCT clause in aggregates. Finally, a first 
step towards SQL syntax error reporting has been done: undefined 
tables, views and columns in a SQL statement are reported, and similar 
existing entries are suggested as alternatives. 

A complete list of enhancements, changes and fixed bugs is attached to 
the end of this message. 
Please, see http://des.sourceforge.net for details.

  Best regards.


==============================================================
Fernando Saenz Perez
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. Ingenieria del Software e Inteligencia Artificial / 
Department of Software Engineering and Artificial Intelligence
Universidad Complutense de Madrid
Facultad de Informatica
C/Profesor Jose Garcia Santesmases, s/n
E - 28040 Madrid. Spain
==============================================================



Version 2.3 of DES (released on May, 24th, 2011)

* Enhancements:
  o SQL declarative debugger: Users can debug SQL views from a declarative 
debugging point-of-view. The system interactively asks questions to the user 
about relations involved in the computation of the debugged view. Trusted 
specifications add semantic references in order to cut the number of questions 
down
  o Added the Datalog tabled metapredicate distinct/1, which computes distinct 
outcomes for its argument, discarding duplicates. It takes effect when 
duplicates are enabled via the command /duplicates on 
  o New Datalog functions and predicates for discarding duplicates along 
aggregation: 
    - Aggregate functions: count_distinct/1, count_distinct/2, avg_distinct/2, 
sum_distinct/2, and times_distinct/2
    - Aggregate predicates: count_distinct/2, count_distinct/3, avg_distinct/3, 
sum_distinct/3, and times_distinct/3
  o Working DISTINCT and ALL keywords in SQL SELECT and UNION statements as of 
SQL2 standard
  o Working DISTINCT and ALL keywords in SQL aggregate functions as of SQL2 
standard
  o Display of SQL statements compilations to Datalog, selectable with the new 
command /show_compilations
  o Output from shell commands in windows applications are logged
  o Compact listings can be enabled so that blank lines in the console output 
are removed
  o New commands:
    - /debug_sql View [Options] Debug a SQL view, optionally specifying whether 
trusting tables or not, selecting a trust file and selecting a traverse order
    - /show_compilations Display whether compilations from SQL DQL statements 
to Datalog rules are to be displayed 
    - /show_compilations Switch Enable or disable display of extended 
information about compilation of SQL DQL statements to Datalog clauses (on or 
off, resp.)
    - /compact_listings Display whether compact listings are enabled 
    - /compact_listings Switch Enable or disable compact listings (on or off, 
resp.)
    - /nospy SPred[/Arity] Removes the spy point on the given predicate in the 
host Prolog interpreter (implementor's command)
    - /debug Set debug mode in the host Prolog interpreter (implementor's 
command)
  o Saving the deductive database to a file also includes constraints (type, 
primary key, functional dependency, foreign key, and user-defined). Restoring a 
database from file also recovers these constraints
  o Added option force to command /save_ddb, which avoids asking the user 
should the file exists already
  o Added help on output without argument
  o Datalog predicate symbols and alphanumeric constants containing extended 
characters do not longer need to be enclosed between quotes
  o SQL correlated queries are also allowed in comparison operators
  o Escaped single quotes allowed in SQL strings
  o SQL syntax error reporting for unknown tables, views and columns. Similar 
table and view names are provided for the user to choose
  o Some run-time errors regarding incorrect use of built-ins (e.g., 
aggregates) are detected earlier during compilation
  o Improved clpfd library for Ciao port, which allows to support type checking 
(thanks to Rémy Haemmerlé) 
  o New port to SWI-Prolog 5.10.4
  
* Changes:
  o SQL natural joins keep the order of columns in the projection list, as 
usual in RDBMS implementations  
  
* Fixed bugs:
  o Queries involving equality between nulls at the system prompt were 
incorrect. Bug introduced in version 2.1
  o When requesting help on a keyword which is both a command and a built-in 
(e.g., log), only help on command was displayed
  o Some synomys in the help were not displayed
  o Type error raised when creating SQL views involving TIMES aggregate function
  o Single quotes inside quoted atoms were allowed
  o Predicate/Arity specifications in commands did not apply for arities 
greater than 9
  o Removing the compilation of nested applications of outer joins in SQL left 
some unremoved rules (when submitting SQL queries and droping views)
  o Some safety warnings during compilation of some aggregate predicates were 
raised, even avoiding to solve some safe queries
  o After executing an INSERT, DELETE and UPDATE involving other (nested) SQL 
statements, the extension table was not cleared (so, an answer entry might 
occur in the table after finishing the modification statement)
  o Some incorrect SQL statements involving unexistent columns were not rejected