General

This version contains many bug fixes, performance enhancements, and powerful extensions.

News

FLORA-2 is now distributed under the Apache License 2.0.

The following new features have been added to FLORA-2 in this release:

• Defeasible rules.
• Rule Ids and tags (for defeasible reasoning) can be specified.
• Explicit negation neg.
• User-defined functions.
• Delay quantifiers, which allow goal reordering at runtime.
• Hypothetical operators of Transaction Logic (possible <> and not possible ~<>).
• Incremental tabling is supported (subject to the limitations of XSB).
• Sensor predicates.
• Low-level predicates.
• Table dump and non-termination analysis utilities.

General

FLORA-2 has undergone significant changes to make it more of a Web language. The system has also become more robust and many interfaces and enhancements were added. The syntax has been changed somewhat to make FLORA-2 better aligned with other Semantic Web languages and, especially, with other F-logic based languages. This resulted in incompatible changes with respect to version 0.94 (see below; a special script is provided to simplify conversion of old programs to the new syntax).

News

• A new Java API
• A new Eclipse-based editor/visualizer.
• It is now possible to save the current state of a module in a file.
• Directive for importing one module into another.
• The meta-decomposition operator =.. now works not only for Prolog terms but also for HiLog terms and for reified formulas.
• It is now possible to specify the type (signature) of a Boolean method.
• Cardinality constraints can now be specified in class signatures. There are now standard methods for checking type and cardinality constraints. They are defined for classes Type and Cardinality, respectively, in the system module _typecheck.
• Structured primitive types, such as dateTime, time, IRI, etc.
• New syntax for compacr URIs to simplify specification of Web resources.
• New system library for reading and parsing terms from standard input, strings, and files.

Backward Incompatibility

Major incompatible changes of syntax: Some aspects of the syntax has been aligned with other rule languages for the Web and with F-logic based systems. There is a Perl script, convert.pl, in the Misc subdirectory, which can greatly simplify conversion of the old FLORA-2 programs. The file Misc/README explains how to use this program.

• Variables now start with ? and uppercase alphanumeric atoms do not need to be quoted.
• Transactional methods are now designated with the prefix % instead of #.
• The equality(flogic) option in the setsemantics directive has been deprecated.
• The meaning of path expressions in the head of a rule has changed: they no longer create a new skolem term if the path expression does not have a value. Instead, the body of the rule is considered false in such a case.
• The @prolog() and @prolog(module) module specifications have been changed to @_prolog and @_prolog(module). To sweeten the pill, _plg instead of _prolog is also allowed. Likewise, @prologall() and @prologall(module) have become @_prologall and @_prologall(module), respectively, and the abbreviation _plgall is also accepted.
• The system module syntax @flora(module) has been changed to @_module. For instance, @flora(sys) is now @_sys.
• debug[%check_undefined(on)]@flora(sys) is now Method[%_mustDefine(on)]. The statement debug[%check_undefined(on,foomodule)]@flora(sys) is now Method[%_mustDefine(on(foomodule))], etc. The statement debug[%ignore_undefcheck(...)] is now Method[%_mustDefine(off,...).
• The builtins that start with fl, like flDemo, flEnd, etc., are now called _demo, _end, and the like. flImport is now '_flimport'.
• Pretty printing is now provided by a package rather than a system module. Invocation now differs slightly.
• In-place module, which allows the user to type a program at command line is now . (period) instead of the keyword user (i.e., one types [.] instead of [user]).

General

The development of FLORA-2 has continued unabated. Apart from making the system more robust, we added a large number of enhancements. The syntax has also been cleaned up, which resulted in incompatible changes with respect to version 0.92 (see below).

News

• Modules can now be encapsulated. A module can export methods and predicates to all modules our to a particular list of predicates.
• One can now reify rules in addition to facts and other formulas.
• The new directives setsemantics{...} and semantics{...} allow the programmer set and query the semantics of any module.
• It is now possible to use "and" and "or" instead of "," and ";" when the latter mean conjunction and disjunction, respectively.
• A new predicate, flora_query, can now be used to send arbitrary queries to FLORA-2 from the Prolog side. This means that one can use the XSB C or Java interfaces to send queries to FLORA-2 through an intermediate Prolog module.
• The clause{...} primitive lets one query the rule base.
• The commands flAdd file and [+file] can now add contents to modules instead of erasing it. The command flCompileAdd is used to compile files for later loading into a module. It does not by itself load any files.
• Enhanced checking for undefined methods and predicates. The new directive #ignore_undefcheck allows to selectively relax checks for undefinedness in cases where such checks are undesirable.
• The following types are now predefined: integer, float, number, symbol, (a,b), (a;b), (a-b).
• There is now a rudimentary run-time optimizer, which the user can turn of and off dynamically. See flOptimize.
• Inheritance-less inheritance(none) semantics is now supported in addition to the usual semantics where inheritance is the default.
• Experimental support for persistent FLORA-2 modules, which are stored in a database through the ODBC interface.
• Experimental support for XML/HTML/SGML parsing and XPath queries.

Backward Incompatibility

• Major incompatible change of syntax: HiLog predicates are now tabled by default. Non-tabled predicates must now be prefixed with a #, by analogy with non-tabled methods. The table directive has been deprecated.
• The symbol % is no longer starting a comment. Use /*...*/ and // instead. The symbol % will be reused for other purposes.
• The "equality" directive has been deprecated. Use the new setsemantics directive.
• Constructs like a[attr=> {b,c}] and a[attr=>> {b,c}] are no longer legal (i.e., the curly braces in the context of => or =>>). Use a[attr=> (b,c)] and a[attr=>> (b,c)] instead.
• Prolog predicates call/1 and findall/3 are no longer special in FLORA-2 and should be avoided, since call/1 is redundant and findall/3 is superseded by the aggregate operators such as collectset{...}.

General

FLORA has undergone many changes and a great number of features were added. Some changes make the syntax of the present version incompatible with earlier versions. However, these changes simplify the language and improve its usability. It is the first version that is reasonably feature-complete and thus can be called a "beta".

News