[Apologies for multiple receptions]
Hello.
This is a mail just for informing that the new release
Datalog Educational System version 2.7
has been launched on January, 3rd, 2012, and ported to
Ciao Prolog 1.14.2
The most relevant enhancement in current release is the
addition of an extended relational algebra processor. It
includes all the original operators but division, and
extended operators for dealing with outer joins, duplicate
elimination, recursion, and grouping with aggregates. Syntax
follows WinRDBI [Diet01], so that in particular all of its
examples run straight on DES. Another useful improvement is
a new switchable multi-line mode, allowing entering inputs
which span over several lines. This applies to both the
command prompt and the processing of batch files, and it is
enabled with the command /multiline on. Supported SQL
language has been extended a bit with new clauses for DDL
statements, as well as for metadata information. Parsing of
Datalog and SQL files and inputs has been enhanced: it now
runs faster and appropriately handles operators. Column and
relation renamings in SQL statements have been revisited and
several issues have been solved.
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 2.7 of DES (released on January, 3rd, 2012)
* Enhancements:
o Extended relational algebra processor including all the
original operators but division, and extended operators
for dealing with outer joins, duplicate elimination,
recursion, and grouping with aggregates
o Multi-line input is also allowed in addition to the
current single-line input. Long inputs as typical SQL
statements can be spanned over several lines. When
multi-line is enabled with the command /multiline on,
Datalog inputs must end with a dot (.), and SQL and RA
inputs with a semicolon (;). When disabled, each line is
considered as a single (Datalog, SQL or RA) input and
ending characters are optional
o When multi-line input is enabled, remarks enclosed
between /* and */ can span over several lines and can be
nested as well
o Single-line (--) and multi-line (/**/) remarks can be
included in SQL statements at any place a separating blank
can occur
o SQL statement CREATE TABLE can include LIKE for creating
a table with the same schema as an existing one
o SQL statement DROP TABLE can include IF EXISTS clause
and can apply to a list of tables
o New (non-standard) SQL metadata statements (catalogued
under ISL, Information Schema Language):
+ SHOW TABLES; List table names. TAPI enabled
+ SHOW VIEWS; List view names. TAPI enabled
+ SHOW DATABASES; List database names. TAPI enabled
+ DESCRIBE Relation; Display schema for Relation, as
/dbschema command does. TAPI enabled
o New commands:
+ /list_tables List table names. TAPI enabled
+ /list_views List view names. TAPI enabled
+ /multiline Display whether multi-line input is enabled
+ /multiline Switch Enable or disable multi-line input
(on or off resp.)
+ /ra Switch to RA interpreter
+ /ra Query Execute an RA query
+ /referenced_relations Name Display relations directly
referenced by a foreign key in Name
+ /referenced_relations Name/Arity Display relations
directly referenced by a foreign key in Name/Arity
o Last line in a processed file must not end with a
carriage return for its processing
o Faster abolish command and drop database SQL statement
o Display of the number of consulted constraints, if any
o Exceptions during constraint checking when consulting
files are caught
o Faster parsing of Datalog rules and SQL statements
o A pivot variable that does not occur in the aggregate
relation raises a syntax error
o Views are not required to be created with given column
names
o Submitting a query or creating a view with duplicated
columns is rejected
o Language command error messages instead of just "Input
processing error"
o Improved compilation of EXISTS SQL clauses, using
Datalog built-in top/2, which allows to prune the number
of computed tuples
* Changes:
o The system prompt for Datalog language changes to the
old prompt DES>, as almost any input can be handled from
this setting. The only inputs that must explicitly
submitted to a language processor are those that can be
handled by several language processors
o Null identifiers are not wasted as eagerly as in
previous versions
o Negation algorithm et_not do not longer rely on
computations by strata
o New organization of system files:
+ des_sql_debug.pl (debugger extracted from former
des_sql.pl)
+ des_dl_debug.pl (replaces des_debug.pl), and
+ des_ra.pl (includes RA processor)
* Fixed bugs:
o Listings of SQL statements including Top-N queries
failed
o After submitting an incorrect SQL view, all of its
temporary schema was not cleaned up
o Variable names in consulted Datalog constraints were
lost
o New schema names defined in the list of local
definitions inside a WITH or ASSUME SQL statement were not
handled appropriately. Bug introduced in version 2.6
o Only one blank was allowed after a SELECT statement. Bug
introduced in version 2.6
o Operator precedence in SQL conditions and Datalog bodies
was not correctly handled (parentheses were needed to
ensure correct operator applications)
o Renamed relations could not be enclosed between
parentheses
o A renamed argument in a nested query was not visible for
the WHERE condition of its outer query
o Expressions in nested SQL queries could not be
referenced from outermost queries
o Type inference failed in some situations for equivalent
internal string types (cf. russell.sql). Bug introduced in
version 2.6
o Underscored variables in a head rule made rule assertion
fail
o The Prolog interpreter did not handle conjunctive and
disjunctive queries