The DLV Project
A Disjunctive Datalog System (and more)

About DLV

DLV is a system for disjunctive datalog with constraints, true negation (à la Gelfond & Lifschitz) and queries.

The DLV system also includes

• the K planning system,
• a frontend for abductive diagnosis and Reiter's diagnosis,
• support for inheritance, and
• an SQL frontend which prototypes some novel SQL3 features.

(You may want to check our entry in the Library of Logic Programming Systems and Test Cases at Koblenz.)

The Team

Core

Nicola Leone, Gerald Pfeifer, Wolfgang Faber

Contributors

Francesco Calimeri, Mina Catalano (Student), Tina Dell'Armi, Giuseppe Ielpa (Emeritus), Vincenzino Lio (Student), Simona Perri, Axel Polleres (Emeritus), Francesco Ricca

Affiliates

Thomas Eiter, Georg Gottlob, Giovambattista Ianni, Francesco Scarcello

Former team members

Robert Bihlmeyer (student), Antonella Capalbo (student), Manuela Citrigno (student), Simona Citrigno (student), Chiara Cumbo (student), Christoph Koch (student, affiliate), Cristinel Mateis (staff), Lothar Mauerhofer (student), Domenico Rosaci (student)

Have a look at our gallery!

Download

DLV is free for academic and non-commerical educational use, as well as for use by non-profit organisations. For the full license and further information for commercial use, run DLV with the option -license.

DLV is actively developed. To receive notifications about new releases and other important events regarding DLV, just drop us a note at the addresses specified at the end of this page.

Please always use the most current version of DLV (cf. version history) and have a look at our benchmark page!

Note that the current release does not yet contain a full implementation of magic sets. You can get a snapshot version with magic sets from the magic page.

We offer a command-line version in binary form for i386-linux-elf-static (also usable on FreeBSD), i386-apple-darwin (Intel MacOS X), powerpc-apple-darwin (PowerPC MacOS X), and Windows 95/98/NT/2000/XP.

Note that the above binaries do not come with ODBC. On MacOS, just download the file as dlv, say, make it executable (running chmod a+rx dlv), and you are ready to go and can run DLV as dlv or ./dlv.

Below, we provide some versions with the ODBC interface. Note that due to technical reasons, these are dynamically linked, which means that you will need all of the required libraries, in particular the odbc library, in the path of your dynamic linker. You can check which libraries are needed and whether your linker finds them using the ldd command on most systems (on Darwin/Mac OS X use otool -L).

Version requiring libodbc.so of unixODBC: i386-linux-elf.

Version requiring iodbc (comes with Mac OS X): i386-apple-darwin (Intel MacOS X), powerpc-apple-darwin (PowerPC MacOS X)

Version requiring odbc32.dll (comes with Windows): Windows 95/98/NT/2000/XP

Note that some of the ODBC binaries are not well-tested. Any feedback is appreciated.

Documentation & Examples

We provide a full-fledged online manual; also the following examples might be interesting:

• Examples we have presented at LPNMR'97.
• Instances of 3SAT we have used for our KR'98 paper.
  (The files are called vX.cY, where X and Y are the number of variables and clauses, respectively.)
• Ladder graphs we have used for our FQAS'98 and KR'98 papers.
  (The files are called ladder.X, where X is the number of nodes.)
• Strategic companies instances we have used for our FQAS'98 and KR'98 papers.
  (The files are called X.3, where X refers to the number of companies and 3 indicates that three times as many products as companies exist.)
• A generator for instances of strategic companies in C++.
• A disjunctive encoding of 3-Colorability.
• A disjunctive encoding of Hamiltonian Cycle.
• A fast Blocks World encoding including some problem instances. This encoding is a DLV version of the Blocks World encoding presented by I. Niemela in "Logic Programs with Stable Model Semantics as a Constraint Programming Paradigm" (1998).

Finally, there is a nice tutorial by Christoph Koch.

Related Work

The DLV Wrapper by Francesco Ricca and Nicola Leone is maintained at the Università della Calabria. It provides a Java interface to DLV.

dlvex is an extension to the DLV system providing access to "external predicates" which are supplied via libraries. It is maintained by members of the DLV team from Università della Calabria and will eventually be integrated into mainline DLV.

DLT is an extension to the DLV system providing reusable template predicate definitions. It is maintained by members of the DLV team from Università della Calabria.

DLV^DB is a further extension to the DLV system which follows a more database-oriented approach.

dlvhex is a system for answer set programming with external computation sources.

NLP-DL is a system for coupling nonmonotonic logic programs with description logics.

James Delgrande, Torsten Schaub and Hans Tompits have created an external frontend for prioritized logic programs.

Vladimir Sarsakov, Torsten Schaub, Hans Tompits and Stefan Woltran have created an external frontend for logic programs with nested expressions.

A-POL, a partial order programming extension for Answer Set Programming, by Mauricio Osorio Galindo and Enrique R. Corona D.

History

October 11th, 2007

Introduce named constants that can be set like #const X = 12.

Improved handling of ranges such as f(X..Y); no longer print range facts as IDB, but properly handle as EDB.

Assorted bug fixes for assignment aggregates, aggregates over the empty set or undefined predicates, and rules with several aggregates.

Add indices to the grounding, including support for aggregates and recursive predicates, which significantly benefits performance in many cases. Avoid the generation of duplicate rules in some initial optimizations. Identify cyclic dependencies between aggregates and bail out in that case. Fix two corner cases, including an issue with backjumping as related to aggregates. Tweak performance, among others by not computing some house keeping data (selectivities) for negative literals.

Fix a crash which could occur for programs with more than 2^15 predicate names.

Make error messages and warnings more consistent. Improve the error message for cases where #maxint is less than the maximum integer occurring in input and when encountering a free variable in #sum, #times, #min or #max which is not an integer. Properly exit with an error code when the grounding fails.

Many improvements to the ODBC interface, including better interoperability, increased stability, better support for larger data sizes and a revamped #export infrastructure.

Several internal cleanups and infrastructure changes in the direction of functional builtins. Increase portability as verified by tests with a wider range of compilers. Make the diagnosis frontend (nearly) reentrant. Handle more error conditions (in user input) gracefully without exiting immediately.

Improved online documentation, especially regarding aggregates, and document non-ground queries.

July 14th, 2006

Support iODBC in addition to unixODBC and offer ODBC support for GNU/Linux, MacOS, and MinGW targets.

Issue warnings when #import and/or #exports statements are used, yet the build does not contain the ODBC interface.

Implement a new version of the backjumping algorithm used in the grounding. This includes improved handling of aggregates. Handle bound literals more efficiently during grounding.

Speed up subsumption checking.

Handle strings of unlimited length throughout all of DLV.

Normalized auxiliary predicate names, which is useful when feeding the output of instantiation back to DLV or other solvers, for example. Revamp handling of internal predicates on the way.

Add a new heuristic criterion based on the degree of support of non-HCF atoms (cf. the LPNMR'05 paper by Faber and Ricca).

Avoid model checks if the program is known to be head cycle free and the GUS computation is active, as all model checks will succeed in this case.

Fix bugs in the propagation of #max aggregates, which could cause some answer sets not being found. Also improve handling of #min aggregates.

More than the usual quota of internal cleanups.

January 12rd, 2006

Add backjumping to the instantiator. This significantly speeds up the generation of ground programs in several relevant examples, and is basically performance neutral in the worst case.

Tune the handling of aggregates with respect to dynamic body reordering in the instantiator, such that aggregates boiling down to variable assignments are considered before other aggregates.

Extend #import to handle predicates that are used as IDB as well.

Check the safety of non-ground queries, and issue an error in case.

Also accept the empty string ("") as a constant now.

For the planning frontend, apply the mutual exclusion stratifiablity check only if the program is unstratified.

Address several minor memory leaks when parsing aggregates and in the grounding. Fix a minor issue with model generation related to #min and #max aggregates.

Address some corner case in the model checker.

Simplify several internals in the grounding and slightly speed up subsumption checking.

Make GCC 3.4 the default compiler we are using, up from GCC 2.95.

Replace the original, Cygwin-based Windows port by one based on MinGW; only the single DLV binary is needed now!

Finally, also the manual has seen several fixes and refinements since our previous release!

As you can see from the list of changes above, many of these stem from the use of DLV for real-world applications. Overall, this release comprises 50+ changesets!

February 23rd, 2005

Support = in addition to == to denote built-in equality; deprecate the == form.

Major restructuring in the ODBC interface code, including the following user-visible changes:
Improve the implementation of #export, and add support for more than one #export statement in one program.
Change the format of the #import command, including type and conversion specifiers.

Improve the manual with sections on PostgreSQL and the ODBC interfaces in general. Address some typesetting issues and one issue wrt. set versus multiset in the section on aggregates. Minor tweaks to the command-line help as well.

Add options -ORb[-] and -ORp[-] which allow to selectively enable/disable the basic and projection rewritings. Previously, only the projection rewriting was disabled by -OR-, now also the basic rewriting.

Address some corner-case where sets in aggregates were not dealt with properly and improve checks for variables in aggregates in general. Fix a bug in the propagation of truth values in #min/#max aggregates.

Avoid some unnecessary propagations in the Model Generator.

Adress a minor issue wrt. the costs for weak constraints. Properly diagnose rules, constraints,... with more variables than the grounding can handle.

Adjustments in the heuristics on the sizes of tables (predicates) which guide the grounding.

May 23rd, 2004

dlv -v now prints the version, and dlv without any options provides usage info instead of assuming empty input.

When only computing the grounding (with -instantiate), DLV version information is now always emitted as a comment, plus we made some further changes to make -instantiate output valid input for both DLV and Lparse.

Command-line options -filter= and -pfilter= now also accept comma separated lists of predicate names.

Several improvements in the online manual, especially concerning aggregates; remove all remaining traces of obsolete command-line options -FB and -FC.

Properly detect and diagnose the (incorrect) use of true negation for terms. Detect and diagnose all misuses of true negation for atoms at once, instead of just the first occurrence.

Improve the new model checking optimizations introduced with the previous release to increase performance (selectively perform model checks also forwards, combine partial checks forwards and backwards, avoid checks forwards for HCF programs). Fix a correctness issue.
Remove command-line options -OPb; introduce -OPf- to control partial model checks.

Improve the dynamic body reordering of the integrated grounded module, fix handling of #succ(X,X), +(X,X,Y), *(X,X,Y) and similiar duplicate occurrences of some variable in builtins, slightly improve the storage of input data, and avoid duplicate work in some corner case.

Add support for non-ground queries.

Add support for subsumption testing and elimination, enabled by a new command-line option -OS.

Lots of bug fixes and refinements in the DLV^K frontend, including

• proper handling of cyclic dependencies among executability conditions,
• section actions, fluents, always, initially, and goal can now appear in any order in the input,
• new support for levelled action costs,
• fix handling of <= and ==,
• fix a bug for #min over an empty set,
• improve handling of duplicate aggregates functions,
• detect and warn about total -f, and generally improve the error messages in the parser.

Handle weak constraints with weight zero.

Many fixes and improvements wrt. aggregates.

Improve statistics output, and continue work to make DLV useful as a module.

Significant work on the ODBC interface (which is not part of the public releases yet).

May 16th, 2003

Significant performance improvements for model checking (especially on hard instances of SigmaP2 problems).

Language enhancements:

• Support for aggregates (#count, #min, #max, #sum, #times), including detailed documentation.
• Facts of the form f(X..Y) where X and Y are (variables bound to) integers are now supported.

Various changes and improvements in DLV^K, including support for FORBIDDEN ... AFTER ..., quoted strings as identifiers, more efficient translations, and new options -planminactions and -planmaxactions.
Also we now just warn (instead of refusing to proceed) if the background knowledge is unstratified. In any case, though, it still has to have a unique answer set!

Various changes in statistics (option -stats), including the addition of "structural size", improved support of statistics when using option -instantiate, and new statistics "Partial Model Check time" and "Total Model Check time" where "Model Checker time" now is the sum of these two.

Assorted fixes related to option -wctrace, memory usage, and subset-minimal diagnosis a la Reiter.

Remove command-line options -OMb and -OMb-, the former of which has been default for years and is now hard-wired.
Rename options -FB and -FC to -brave and -cautious, respectively, still supporting the old variants for backwards compatibility.

Add a new option -satlike which, when used with -instantiate, allows for using DLV as external instantiator more easily and efficiently.

April 12th, 2002

A bug-fix release with a hugely improved DLV^K frontend.

Several memory leaks have been fixed. The parser is now a bit more strict, but a query doesn't need to be followed by a newline any longer.
Several fixes and improvements wrt. weak constraints; options -costbound and -wctrace are now mutually exclusive.
Improved statistics output, and statistics are provided in more (corner) cases.

Lots of enhancements and fixes to DLV^K, including new support for planning with costs, extended syntax for inertial, new forbidden macro, new options -FPsoundcheck and -FPcompletecheck, and much more!
The output has been slightly changed. Specifying a goal is now mandatory.

June 11th, 2001

Significant improvements of heuristics employed by the Model Generator. Specifically, we now weigh the cost of both taking a literal true and taking it false, and we reduced the cost of computing heuristics in many relevant cases. (See our forthcoming IJCAI and LPNMR papers for details.) Note that, while this brings nice speedups in general, there are, as usual with heuristics, specific cases which may experience some slowdown.

Adopt a stronger pruning operator on head-cycle free programs. This coincides with the well-founded operator on disjunction-free programs, but keeps the linear-time efficiency of Fitting's operator on acyclic programs.

Planning Frontend: Add proper checks whether the planning domain in input is proper (Pun intended). A new command-line option -planlength=<N> allows setting the maximum plan length.

Minor bug-fixes in the grounder (option -OG1) and Model Generator (linear-time operators). Better frontend interfaces, which will allow for an easier integration and maintainance of (further) frontends.
Small performance tweaks in the Model Generator and Checker.

Significant performance gains in the grounder due to the use of advanced data structures (similar to those used in database systems) and algorithmic improvements.

Weak Constraints. New command-line option -costbound allows to print those answer sets with cost lower than a specified value.

Completely remove the distinction between EDB and IDB predicates. Both f(X) :- g(X). f(1). and f(1). f(X) :- g(X). are now correct inputs for DLV.

Command-line option -stats revamped; among others it includes the number of choice-points and the number of answer sets printed.
And last but not least, the command-line option -n=<N> now works correctly with the planning frontend when security checks are performed.

October 15, 2000

Language and Functionality
A new language feature, namely weak constraints (with weights, layers, or both; see [BLR97b] for details), has been added, together with a new command-line option -costbound=<n> to perform optimization tasks.
New command-line option -instantiate that prints the grounded version of the input program.
New command-line option -det that prints the deterministic consequences of the input program, which is a superset of the well-founded semantics approximating the intersection of all answer sets.
Use lexicographic comparison when dealing with string literals and constant symbols (instead of a fixed, but arbitrary ordering).
Model Checker
The model checking strategy has been improved and the SAT checker SATZ has been integrated into the system. These measures led to a tremendous performance improvement (up to 2 orders of magntude) in internal tests.
Error Messages and Bugfixes
Several error messages have been improved, a small memory leak has been plugged, some minor bugs that would only trigger under rare circumstances have been fixed.
A few minor improvements and fixes in the K planning frontend.

April 5, 2000

Frontends
New planning frontend for the language K, which is a logic-based planning language well-suited for representing incomplete knowledge.
Include the existing inheritance frontend directly into the dlv kernel, also making various improvements.
Grounding
Lots of changes to data structures and algorithms bring a significant speed-up for applications with huge amount of data.
Parsing
It is now possible to specify facts for IDB predicates. In other words, input like f(X) :- g(X). f(1). works just fine now.
With the next release we plan also support the symmetric case: f(1). f(X) :- g(X). thus completely removing the distinction between EDB and IDB.
#maxint can be set from the datalog input by means of the new #maxint=127. construct.
Improve a couple of error messages.
The parser is stricter in several instances now, but does not abort upon the first error any longer.
Change the name from dlv to DLV officially.

November 24, 1999

Significant speed-up of the Model Checker for hard problems (up to a factor of 25 on overall execution time for some examples).
Significant improvement of various internal data structures; much better performance when parsing and grounding large input; support for programs of unlimited size.
Reduced memory consumption.
New command-line option "--" that makes dlv operate as a filter.
The SQL Frontend is now invoked by means of the new command-line option -FS.
Improved error handling and various minor fixes.

October 16, 1999

Add a special grounding pass for propositional input.
Beef up heuristics used by the Model Generator.
Most incredible speedup of the dependency graph handler (which is used all over the system).
Lots of tweaks to the Model Checker, plus we don't invoke the full Checker for trivial problems any more.
Change data structures to significantly reduce memory consumption on hard problems; this is also somewhat faster. In addition, fix two huge memory leaks.
Optimize input preprocessing and fix treatment of some corner-cases.
Fix a bug in the Grounding which could (in theory) have led to the loss of models.
The timers are now more acurate and fine-grained, but must be run on a completely unloaded machine.

What does this mean in practice? One of the instances of prime implicants in our internal benchmarks suite, for example, went from 10.272s to 0.980s on a Pentium II/400 running FreeBSD. ;-)

June 08, 1999

Add heuristics to the Model Generator, which results in quite some speedup on hard instances; this can be disabled by -OH-.
Two examples illustrate the progress we have recently made:

	April 06 1999	May 28 1999	June 08 1999
Blocksworld P4	> 1000s	194s	39s
Hamilton Path (25 nodes, 60 arcs)	> 1000s	716s	12.7s

Improve error handling in the parser.
Use egcs 1.1.2 instead of egcs 1.1 on all platforms except alpha-dec-osf4.0; upgrade i386-unknown-freebsd2.2.7 to i386-unknown-freebsdelf3.1; add a i386-pc-solaris2.7 port.

May 28, 1999

Improved "propagation of deterministic consequences", which prunes the search space significantly bringing relevant performance gains.
Apply relational database techniques which reduce the size of the ground instantiation; this can be disabled by -OR-.
By default, input facts are now included in the output as well; new options -facts and -nofacts control this feature.
Allow for ";" and "|" as alternate notions for disjunction; the keywords "non" and "not" are now case-sensitive.
Significantly increase the maximal number of predicates and constants; remove obsolete options -OCi and -pipe; bugfix, where in some cases a "," was omitted when printing models.

Apr 06 1999

Numerous performance improvements, mostly in the model generator: new "must-be-true" truthvalue made explicit; more efficient backtracking; enhanced propagation code; additional propagations because of "must-be-true"; improved program preprocessing.
Bugfix concerning the model checker and generator interaction; in the Reiter subset minimal diagnosis frontend, additional checks on the theory's validity are performed; better statistics.
Finally, we do no longer provide a binary for i386-linux-elf-gnulibc1.

Feb 10 1999

Linear time operators for deterministic inferences for rules and constraints and other major improvements in the Model Generator; linear time operators also for the well-founded computation; more efficient storage of interpretations which also significantly reduces memory consumption; possibly true literals instead of conjunctions in the Model Generator; improved Grounding in the presence of negative literals; command-line option -OV* has been obsoleted; new option -OMb-; significant improvements of the Model Checker; for rather hard instances, the model generator of dlv itself is now invoked to solve the co-NP complete problem of model checking.
Altogether, we are happy to report the following improvements over those results presented in our KR'98 paper (run on the same machine, of course):

	KR'98	now
Prime implicants (47 variables, 202 clauses):	1628.5s	0.3s
Strategic Companies (71 companies, 213 products):	2348.8s	45.4s

Nov 21 1998

Correctly handle hypotheses in heads in the Reiter's diagnosis frontend; .obs and .hyp files no longer set the -FD mode automatically; various major bugfixes in the diagnosis frontend; improvements in the model checker.

Nov 09 1998

Allow [0,0] as range for integers; various fixes in the diagnosis frontend.

Oct 15 1998

Support for filtering (a.k.a. projections); highly improved model checker; employ a Fitting-style operator by default; bugfix speeding up certain disjunctive programs tremendously; more intuitive and less misleading output; sparc-sun-solaris2.6 instead of sparc-sun-solaris2.5.1; and of course many small bugfixes.

Sep 11 1998

New i386-unknown-freebsd2.2.7 and i386-linux-elf-gnulibc2 ports; first version built with egcs 1.1 instead of egcs 1.0.3a; removed various kludges needed for gcc 2.7.2; new option -OM- to disable Model Checking; option -silent now causes omission of all empty lines in output; synchronized command-line help and manual; added support for anonymous variables.

Sep 05 1998

Official release of full-fledged manual.
(Note that we plan to continually update and improve this; only major changes will be mentioned in this version history.)

Aug 14 1998

New i386-linux-elf-gnulibc1 port; queries are treated more efficiently (datalog, brave and cautious frontends); support for 3=2+1 form of integer arithmetics; -O0 really turns off all optimisations now; various bugfixes concerning constraints and "undefined" atoms; small updates concerning the usage message; various code clean-ups.

Aug 06 1998

New built-ins #int/1 and #succ/2 plus +/3 and */3; alternate option -n=all equivalent to -n=0; support queries in the datalog frontend (i.e., without brave or cautious reasoning); correctly process negative literals in queries; various changes with regard to constraints (no error message if a constraint is always violated, bug fixes,...); removed option -gderes and made -silent more so.

Jul 10 1998

Massive reduction in the amount of memory required (especially on alpha-dec-osf4.0); full support for logical built-ins <, <=, >=, >, ==, <> resp. != (modulo safety requirements); new command-line option -N and predefined constant #maxint.

May 18 1998

New version built with egcs 1.0.3a instead of gcc 2.7.2. Various minor (and not so minor) efficiency enhancements; finer user control over grounding optimizations; support for constraints in theory and further sanity checks in the diagnosis frontend; revamped command-line help; full support for integer constants; cosmetic changes.

May 12 1998

Pre-announcement: We plan to release a new version within 10 days.

Jan 07 1998

Enhanced command-line help (try -help); minor bug-fix (undefined literals in constraints).

Dec 23 1997

New alpha-dec-osf4.0 port; minor bug-fixes.

Dec 01 1997

Full support for Reiter's diagnosis.

Previous versions

...did not carry a real version identification.

Selected Publications

[AFL10a]

Mario Alviano, Wolfgang Faber, and Nicola Leone. Disjunctive ASP with Functions: Decidable Queries and Effective Computation. In 26th International Conference on Logic Programming (ICLP-2010), 2010.

[AFL10b]

Mario Alviano, Wolfgang Faber, and Nicola Leone. Disjunctive ASP with Functions: Decidable Queries and Effective Computation. Theory and Practice of Logic Programming, 26th Int'l. Conference on Logic Programming (ICLP'10) Special Issue, 10((4-6)):497-512, July 2010.

[AFGL09]

Mario Alviano, Wolfgang Faber, Gianluigi Greco, and Nicola Leone. Magic sets for disjunctive datalog programs. Technical Report 09/2009, Dipartimento di Matematica, Università della Calabria, Italy, 2009. url http://www.wfaber.com/research/papers/TRMAT092009.pdf.

[BFL09]

Annamaria Bria, Wolfgang Faber, and Nicola Leone. Normal form nested programs. Fundamenta Informaticae, 96(3):271-295, 2009.

[CCIL09a]

Francesco Calimeri, Susanna Cozza, Giovambattista Ianni, and Nicola Leone. An ASP System with Functions, Lists, and Sets. In Esra Erdem, Fangzhen Lin, and Torsten Schaub, editors, Logic Programming and Nonmonotonic Reasoning --- 10th International Conference (LPNMR 2009), volume 5753 of Lecture Notes in Computer Science, pages 483-489. Springer Verlag, September 2009.

[CCIL09b]

Francesco Calimeri, Susanna Cozza, Giovambattista Ianni, and Nicola Leone. Magic Sets for the Bottom-Up Evaluation of Finitely Recursive Programs. In Esra Erdem, Fangzhen Lin, and Torsten Schaub, editors, Logic Programming and Nonmonotonic Reasoning --- 10th International Conference (LPNMR 2009), volume 5753 of Lecture Notes in Computer Science, pages 71-86. Springer Verlag, September 2009.

[RGS+09]

Francesco Ricca, Lorenzo Gallucci, Roman Schindlauer, Tina Dell'Armi, Giovanni Grasso, and Nicola Leone. OntoDLV: an ASP-based system for enterprise ontologies. Journal of Logic and Computation, 2009.

[BFL08]

Annamaria Bria, Wolfgang Faber, and Nicola Leone. Normal form nested programs. In Steffen Hölldobler, Carsten Lutz, and Heinrich Wansing, editors, Proceedings of the 11th European Conference on Logics in Artificial Intelligence (JELIA 2008), volume 5293 of Lecture Notes in Computer Science, pages 76-88. Springer Verlag, September 2008.

[CCIL08a]

Francesco Calimeri, Susanna Cozza, Giovambattista Ianni, and Nicola Leone. Computable Functions in ASP: Theory and Implementation. In Proceedings of the 24th International Conference on Logic Programming (ICLP 2008), volume 5366 of Lecture Notes in Computer Science, pages 407-424, Udine, Italy, December 2008. Springer.

[CCIL08b]

Francesco Calimeri, Susanna Cozza, Giovambattista Ianni, and Nicola Leone. DLV-Complex homepage, since 2008. url http://www.mat.unical.it/dlv-complex.

[CPR08]

Francesco Calimeri, Simona Perri, and Francesco Ricca. Experimenting with Parallelism for the Instantiation of ASP Programs. Journal of Algorithms in Cognition, Informatics and Logics, 63(1-3):34-54, 2008.

[FPL+08]

Wolfgang Faber, Gerald Pfeifer, Nicola Leone, Tina Dell'Armi, and Giuseppe Ielpa. Design and implementation of aggregate functions in the dlv system. Theory and Practice of Logic Programming, 8(5-6):545-580, 2008.

[MRFL08]

Marco Maratea, Francesco Ricca, Wolfgang Faber, and Nicola Leone. Look-back techniques and heuristics in dlv: Implementation, evaluation and comparison to qbf solvers. Journal of Algorithms in Cognition, Informatics and Logics, 63(1-3):70-89, 2008.

[TDPL08]

Giorgio Terracina, Erika De Francesco, Claudio Panetta, and Nicola Leone. Enhancing a DLP system for advanced database applications. In Proceedings of the International Conference on Web Reasoning and Rule Systems (RR 2008), Karlsruhe, Germany, 2008. Springer Verlag.

[TLLP08]

Giorgio Terracina, Nicola Leone, Vincenzino Lio, and Claudio Panetta. Experimenting with recursive queries in database and logic programming systems. Theory and Practice of Logic Programming, 8:129-165, 2008.

[AFL07]

Mario Alviano, Wolfgang Faber, and Nicola Leone. Using unfounded sets for computing answer sets of programs with recursive aggregates. In Giacomo Fiumara, Massimo Marchi, and Alessandro Provetti, editors, Proceedings of the Italian Conference on Computational Logic (CILC 2007), June 2007.

[Alv07]

Mario Alviano. Efficient recursive aggregates evaluation in logic programming. Master's thesis, University of Calabria, Department of Mathematics, Rende (CS), Italy, 2007. (PDF)

[CCI07]

Francesco Calimeri, Susanna Cozza, and Giovambattista Ianni. External sources of knowledge and value invention in logic programming. Annals of Mathematics and Artificial Intelligence, 50(3-4):333-361, 2007.

[DGL+07]

Tina Dell'Armi, Lorenzo Gallucci, Nicola Leone, Francesco Ricca, and Roman Schindlauer. OntoDLV: an ASP-based System for Enterprise Ontologies. In Proceedings ASP07 - Answer Set Programming: Advances in Theory and Implementation, 2007.

[FGL07]

Wolfgang Faber, Gianluigi Greco, and Nicola Leone. Magic Sets and their Application to Data Integration. Journal of Computer and System Sciences, 73(4):584-609, 2007.

[FL07]

Wolfgang Faber and Nicola Leone. On the Complexity of Answer Set Programming with Aggregates. In Chitta Baral, Gerhard Brewka, and John S. Schlipf, editors, Logic Programming and Nonmonotonic Reasoning --- 9th International Conference, LPNMR 2007, volume 4483 of Lecture Notes in AI (LNAI), pages 97-109, Tempe, AZ, USA, May 2007. Springer Verlag.

[FLMR07]

Wolfgang Faber, Nicola Leone, Marco Maratea, and Francesco Ricca. Experimenting with Look-Back Heuristics for Hard ASP Programs. In Chitta Baral, Gerhard Brewka, and John S. Schlipf, editors, Logic Programming and Nonmonotonic Reasoning --- 9th International Conference, LPNMR 2007, volume 4483 of Lecture Notes in AI (LNAI), pages 110-122, Tempe, AZ, USA, May 2007. Springer Verlag.

[FLPR07]

Wolfgang Faber, Nicola Leone, Gerald Pfeifer, and Francesco Ricca. On look-ahead heuristics in disjunctive logic programming. Annals of Mathematics and Artificial Intelligence, 51(2-4):229-266, 2007.

[LFP+07]

N. Leone, W. Faber, G. Pfeifer, A. Bria, F. Calimeri, G. Catalano, S. Cozza, T. Dell'Armi, T. Eiter, G. Gottlob, G. Greco, G. Ianni, G. Ielpa, M. Maratea, C. Panetta, S. Perri, F. Ricca, F. Scarcello, and G. Terracina. DLV: An Advanced System for Knowledge Representation and Reasoning. ALP Newsletter, 20(3-4), December 2007. Online at url http://www.cs.kuleuven.be/ dtai/projects/ALP/newsletter/dec07/content/Systems/paper.pdf.

[PSCL07]

Simona Perri, Francesco Scarcello, Gelsomina Catalano, and Nicola Leone. Enhancing DLV instantiator by backjumping techniques. Annals of Mathematics and Artificial Intelligence, 51(2-4):195-228, 2007.

[RL07]

Francesco Ricca and Nicola Leone. Disjunctive Logic Programming with types and objects: The DLV⁺ System. Journal of Applied Logics, 5(3):545-573, 2007.

[CFLP06]

Francesco Calimeri, Wolfgang Faber, Nicola Leone, and Gerald Pfeifer. Pruning Operators for Disjunctive Logic Programming Systems. Fundamenta Informaticae, 71(2-3):183-214, 2006.

[CI06a]

Francesco Calimeri and Giovambattista Ianni. Extending ASP by Value Invention. In Marco Gavanelli and Tony Mancini, editors, Incontro del Gruppo di Lavoro Rappresentazione della Conoscenza e Ragionamento Automatico (RCRA) dell'Associazione Italiana per l'Intelligenza Artificiale (AI*IA) dal titolo ``Analisi Sperimentale e Benchmark di Algoritmi per l'Intelligenza Artificiale'', Udine, Italy, June 2006.

[CI06b]

Francesco Calimeri and Giovambattista Ianni. Template programs for Disjunctive Logic Programming: An operational semantics. AI Communications, 19(3):193-206, 2006.

[LPF+06]

Nicola Leone, Gerald Pfeifer, Wolfgang Faber, Thomas Eiter, Georg Gottlob, Simona Perri, and Francesco Scarcello. The DLV System for Knowledge Representation and Reasoning. ACM Transactions on Computational Logic, 7(3):499-562, July 2006. (PostScript)

[RFL06]

Francesco Ricca, Wolfgang Faber, and Nicola Leone. A Backjumping Technique for Disjunctive Logic Programming. AI Communications -- The European Journal on Artificial Intelligence, 19(2):155-172, 2006.

[CFLP05]

Francesco Calimeri, Wolfgang Faber, Nicola Leone, and Simona Perri. Declarative and Computational Properties of Logic Programs with Aggregates. In Nineteenth International Joint Conference on Artificial Intelligence (IJCAI-05), pages 406-411, August 2005.

[CI05]

Francesco Calimeri and Giovambattista Ianni. External sources of computation for Answer Set Solvers. In Chitta Baral, Gianluigi Greco, Nicola Leone, and Giorgio Terracina, editors, Logic Programming and Nonmonotonic Reasoning --- 8th International Conference, LPNMR'05, Diamante, Italy, September 2005, Proceedings, volume 3662 of Lecture Notes in Computer Science, pages 105-118. Springer Verlag, September 2005.

[FLR05]

Wolfgang Faber, Nicola Leone, and Francesco Ricca. Solving Hard Problems for the Second Level of the Polynomial Hierarchy: Heuristics and Benchmarks. Intelligenza Artificiale, 2(3):21-28, 2005.

[FR05]

Wolfgang Faber and Francesco Ricca. Solving Hard ASP Programs Efficiently. In Chitta Baral, Gianluigi Greco, Nicola Leone, and Giorgio Terracina, editors, Logic Programming and Nonmonotonic Reasoning --- 8th International Conference, LPNMR'05, Diamante, Italy, September 2005, Proceedings, volume 3662 of Lecture Notes in Computer Science, pages 240-252. Springer Verlag, September 2005.

[RLD+05]

Francesco Ricca, Nicola Leone, Valerio De Bonis, Tina Dell'Armi, Stefania Galizia, and Giovanni Grasso. A DLP System with Object-Oriented Features. In Chitta Baral, Gianluigi Greco, Nicola Leone, and Giorgio Terracina, editors, Logic Programming and Nonmonotonic Reasoning --- 8th International Conference, LPNMR'05, Diamante, Italy, September 2005, Proceedings, volume 3662 of Lecture Notes in Computer Science, pages 432-436. Springer Verlag, September 2005.

[CCC+04]

Francesco Calimeri, Manuela Citrigno, Chiara Cumbo, Wolfgang Faber, Nicola Leone, Simona Perri, and Gerald Pfeifer. New dlv features for data integration. In JELIA, pages 698-701, 2004.

[CFGL04]

Chiara Cumbo, Wolfgang Faber, Gianluigi Greco, and Nicola Leone. Enhancing the magic-set method for disjunctive datalog programs. In Proceedings of the the 20th International Conference on Logic Programming -- ICLP'04, volume 3132 of Lecture Notes in Computer Science, pages 371-385, 2004.

[CI04]

Francesco Calimeri and Giovambattista Ianni. DLVEX homepage, since 2004. url http://www.mat.unical.it/ianni/wiki/dlvex.

[CII+04]

Francesco Calimeri, Giovambattista Ianni, Giuseppe Ielpa, Adriana Pietramala, and Maria Carmela Santoro. A system with template answer set programs. In JELIA, pages 693-697, 2004.

[DFI+04]

Tina Dell'Armi, Wolfgang Faber, Giuseppe Ielpa, Nicola Leone, and Gerald Pfeifer. System Description: DLV with Aggregates. In Vladimir Lifschitz and Ilkka Niemelä, editors, Proceedings of the 7th International Conference on Logic Programming and Non-Monotonic Reasoning (LPNMR-7), volume 2923 of LNAI, pages 326-330. Springer, January 2004.

[EFL+04]

Thomas Eiter, Wolfgang Faber, Nicola Leone, Gerald Pfeifer, and Axel Polleres. A Logic Programming Approach to Knowledge-State Planning: Semantics and Complexity. ACM Transactions on Computational Logic, 5(2):206-263, April 2004.

[EP04]

Thomas Eiter and Axel Polleres. Towards automated integration of guess and check programs in answer set programming. In Vladimir Lifschitz and Ilkka Niemelä, editors, Proceedings of the Seventh International Conference on Logic Programming and Nonmonotonic Reasoning (LPNMR-7), volume 2923 of Lecture Notes in AI (LNAI), pages 100-113, Fort Lauderdale, Florida, USA, January 2004. Springer.

[MR04]

Victor W. Marek and Jeffrey B. Remmel. Set Constraints in Logic Programming. In Vladimir Lifschitz and Ilkka Niemelä, editors, Proceedings of the 7th International Conference on Logic Programming and Non-Monotonic Reasoning (LPNMR-7), volume 2923 of LNAI, pages 167-179. Springer, January 2004.

[Pfe04]

Gerald Pfeifer. Improving the Model Generation/Checking Interplay to Enhance the Evaluation of Disjunctive Programs. In Vladimir Lifschitz and Ilkka Niemelä, editors, Proceedings of the 7th International Conference on Logic Programming and Non-Monotonic Reasoning (LPNMR-7), volume 2923 of LNAI, pages 220-233. Springer, January 2004.

[CFG03]

Chiara Cumbo, Wolfgang Faber, and Gianluigi Greco. Improving Query Optimization for Disjunctive Datalog. In Francesco Buccafurri, editor, Proceedings of the Joint Conference on Declarative Programming APPIA-GULP-PRODE 2003, pages 252-262, September 2003.

[DFI+03a]

Tina Dell'Armi, Wolfgang Faber, Giuseppe Ielpa, Nicola Leone, and Gerald Pfeifer. Aggregate Functions in Disjunctive Logic Programming: Semantics, Complexity, and Implementation in DLV. In Proceedings of the 18th International Joint Conference on Artificial Intelligence (IJCAI) 2003, pages 847-852, Acapulco, Mexico, August 2003. Morgan Kaufmann Publishers.

[DFI+03b]

Tina Dell'Armi, Wolfgang Faber, Giuseppe Ielpa, Nicola Leone, and Gerald Pfeifer. Aggregate Functions in DLV. In Marina de Vos and Alessandro Provetti, editors, Proceedings ASP03 - Answer Set Programming: Advances in Theory and Implementation, pages 274-288, Messina, Italy, September 2003. Online at url http://CEUR-WS.org/Vol-78/.

[DFI+03c]

Tina Dell'Armi, Wolfgang Faber, Giuseppe Ielpa, Nicola Leone, and Gerald Pfeifer. Semantics and Computation of Aggregate Functions in Disjunctive Logic Programming. Technical Report INFSYS RR-1843-03-07, Institut für Informationssysteme, Technische Universität Wien, April 2003. (PostScript)

[EFF+03]

Thomas Eiter, Wolfgang Faber, Michael Fink, Gerald Pfeifer, and Stefan Woltran. Complexity of Answer Set Checking and Bounded Predicate Arities for Non-ground Answer Set Programming. In Marina de Vos and Alessandro Provetti, editors, Proceedings ASP03 - Answer Set Programming: Advances in Theory and Implementation, pages 69-83, Messina, Italy, September 2003. Online at url http://CEUR-WS.org/Vol-78/.

[EFL+03a]

Thomas Eiter, Wolfgang Faber, Nicola Leone, Gerald Pfeifer, and Axel Polleres. A Logic Programming Approach to Knowledge-State Planning, II: the small DLV ^{cal K} System. Artificial Intelligence, 144(1-2):157-211, March 2003.

[EFL+03b]

Thomas Eiter, Wolfgang Faber, Nicola Leone, Gerald Pfeifer, and Axel Polleres. Answer Set Planning under Action Costs. Journal of Artificial Intelligence Research, 19:25-71, 2003.

[EFLP03]

Thomas Eiter, Wolfgang Faber, Nicola Leone, and Gerald Pfeifer. Computing Preferred Answer Sets by Meta-Interpretation in Answer Set Programming. Theory and Practice of Logic Programming, 3:463-498, July/September 2003.

[EP03]

Thomas Eiter and Axel Polleres. Transforming coNP checks to answer set computation by meta-interpretation. In Proceedings of the 2003 Joint Conference on Declarative Programming APPIA-GULP-PRODE 2003, Reggio Calabria, Italy, September 2003.

[KLP03]

Christoph Koch, Nicola Leone, and Gerald Pfeifer. Enhancing Disjunctive Logic Programming Systems by SAT Checkers. Artificial Intelligence, 15(1-2):177-212, December 2003.

[Pfe03]

Gerald Pfeifer. Solving Hard Disjunctive Logic Programs Faster (Sometimes). In Proceedings of APPIA-GULP-PRODE 2003, Joint Conference on Declarative Programming, pages 226-237, Reggio Calabria, Italy, September 2003.

[Ric03]

Francesco Ricca. The DLV Java Wrapper. In Marina de Vos and Alessandro Provetti, editors, Proceedings ASP03 - Answer Set Programming: Advances in Theory and Implementation, pages 305-316, Messina, Italy, September 2003. Online at url http://CEUR-WS.org/Vol-78/.

[BFL02]

Francesco Buccafurri, Wolfgang Faber, and Nicola Leone. Disjunctive Logic Programs with Inheritance. Theory and Practice of Logic Programming, 2(3), May 2002.

[CFLP02]

Francesco Calimeri, Wolfgang Faber, Nicola Leone, and Gerald Pfeifer. Pruning Operators for Answer Set Programming Systems. In Proceedings of the 9th International Workshop on Non-Monotonic Reasoning (NMR'2002), pages 200-209, April 2002. (PostScript)

[EFL+02a]

Thomas Eiter, Wolfgang Faber, Nicola Leone, Gerald Pfeifer, and Axel Polleres. Answer Set Planning under Action Costs. In Sergio Flesca, Sergio Greco, Giovambattista Ianni, and Nicola Leone, editors, Proceedings of the 8th European Conference on Artificial Intelligence (JELIA), volume 2424 of Lecture Notes in Computer Science, pages 186-197, Cosenza, Italy, September 2002.

[EFL+02b]

Thomas Eiter, Wolfgang Faber, Nicola Leone, Gerald Pfeifer, and Axel Polleres. The DLV ^{cal K} Planning System: Progress Report. In Sergio Flesca, Sergio Greco, Giovambattista Ianni, and Nicola Leone, editors, Proceedings of the 8th European Conference on Artificial Intelligence (JELIA), volume 2424 of Lecture Notes in Computer Science, pages 541-544, Cosenza, Italy, September 2002. (System Description).

[LPF+02a]

Nicola Leone, Gerald Pfeifer, Wolfgang Faber, Francesco Calimeri, Tina Dell'Armi, Thomas Eiter, Georg Gottlob, Giovambattista Ianni, Giuseppe Ielpa, Christoph Koch, Simona Perri, and Axel Polleres. The DLV System. In Sergio Flesca, Sergio Greco, Giovambattista Ianni, and Nicola Leone, editors, Proceedings of the 8th European Conference on Logics in Artificial Intelligence (JELIA), volume 2424 of Lecture Notes in Computer Science, pages 537-540, Cosenza, Italy, September 2002. (System Description).

[LPF+02b]

Nicola Leone, Gerald Pfeifer, Wolfgang Faber, Thomas Eiter, Georg Gottlob, Simona Perri, and Francesco Scarcello. The DLV System for Knowledge Representation and Reasoning. Technical Report cs.AI/0211004, arXiv.org, November 2002. Appearing as [LPF+06]. (PostScript)

[Cal01]

Francesco Calimeri. Progettazione e Sviluppo di Tecniche Di Ottimizzazione per Sistemi di Basi di Conoscenza. Master's thesis, D.E.I.S., Università degli Studi della Calabria, Rende (CS), Italy, 2001. Supported by Nicola Leone.

[CFL+01]

Francesco Calimeri, Wolfgang Faber, Nicola Leone, Simona Perri, and Gerald Pfeifer. DLV - Declarative Problem Solving using Answer Set Programming. In Proceedings of the Seventh Congress of the Italian Association for Artificial Intelligence AI*IA 2001, Bari, Italy, 2001.

[DFI+01]

Tina Dell'Armi, Wolfgang Faber, Giuseppe Ielpa, Christoph Koch, Nicola Leone, Simona Perri, and Gerald Pfeifer. System Description: DLV. In Thomas Eiter, Wolfgang Faber, and Miroslaw Truszczynski, editors, Logic Programming and Nonmonotonic Reasoning --- 6th International Conference, LPNMR'01, Vienna, Austria, September 2001, Proceedings, volume 2173 of Lecture Notes in AI (LNAI), pages 409-412. Springer Verlag, September 2001.

[EFL+01a]

Thomas Eiter, Wolfgang Faber, Nicola Leone, Gerald Pfeifer, and Axel Polleres. System Description: The DLV ^{cal K} Planning System. In Thomas Eiter, Wolfgang Faber, and Miroslaw Truszczynski, editors, Logic Programming and Nonmonotonic Reasoning --- 6th International Conference, LPNMR'01, Vienna, Austria, September 2001, Proceedings, volume 2173 of Lecture Notes in AI (LNAI), pages 413-416. Springer Verlag, September 2001. (PostScript)

[EFL+01b]

Thomas Eiter, Wolfgang Faber, Nicola Leone, Gerald Pfeifer, and Axel Polleres. The DLV ^{cal K} Planning System. In Alessandro Cimatti, Héctor Geffner, Enrico Giunchiglia, and Jussi Rintanen, editors, IJCAI-01 Workshop on Planning under Uncertainty and Incomplete Information, pages 76-81, August 2001.

[EFLP01]

Thomas Eiter, Wolfgang Faber, Nicola Leone, and Gerald Pfeifer. Computing Preferred and Weakly Preferred Answer Sets by Meta-Interpretation in Answer Set Programming. In Alessandro Provetti and Son Tran Cao, editors, Proceedings AAAI 2001 Spring Symposium on Answer Set Programming: Towards Efficient and Scalable Knowledge Representation and Reasoning, pages 45-52, Stanford, California, USA, March 2001. AAAI Press. (PostScript)

[FLP01a]

Wolfgang Faber, Nicola Leone, and Gerald Pfeifer. A Comparison of Heuristics for Answer Set Programming. In Proceedings of the 5th Dutch-German Workshop on Nonmonotonic Reasoning Techniques and their Applications (DGNMR 2001), pages 64-75, April 2001.

[FLP01b]

Wolfgang Faber, Nicola Leone, and Gerald Pfeifer. Experimenting with Heuristics for Answer Set Programming. In Proceedings of the Seventeenth International Joint Conference on Artificial Intelligence (IJCAI) 2001, pages 635-640, Seattle, WA, USA, August 2001. Morgan Kaufmann Publishers. (PostScript)

[FLP01c]

Wolfgang Faber, Nicola Leone, and Gerald Pfeifer. Optimizing the Computation of Heuristics for Answer Set Programming Systems. In Thomas Eiter, Wolfgang Faber, and Miroslaw Truszczynski, editors, Logic Programming and Nonmonotonic Reasoning --- 6th International Conference, LPNMR'01, Vienna, Austria, September 2001, Proceedings, volume 2173 of Lecture Notes in AI (LNAI), pages 288-301. Springer Verlag, September 2001.

[FLPP01]

Wolfgang Faber, Nicola Leone, Simona Perri, and Gerald Pfeifer. Efficient Instantiation of Disjunctive Databases. Technical Report DBAI-TR-2001-44, Institut für Informationssysteme, Technische Universität Wien, Austria, November 2001. Online at url http://www.dbai.tuwien.ac.at/local/reports/dbai-tr-2001-44.pdf.

[LPS01]

Nicola Leone, Simona Perri, and Francesco Scarcello. Improving ASP Instantiators by Join-Ordering Methods. In Thomas Eiter, Wolfgang Faber, and Miroslaw Truszczynski, editors, Logic Programming and Nonmonotonic Reasoning --- 6th International Conference, LPNMR'01, Vienna, Austria, volume 2173 of Lecture Notes in AI (LNAI), pages 280-294. Springer Verlag, September 2001.

[LRS01]

Nicola Leone, Riccardo Rosati, and Francesco Scarcello. Enhancing Answer Set Planning. In Alessandro Cimatti, Héctor Geffner, Enrico Giunchiglia, and Jussi Rintanen, editors, IJCAI-01 Workshop on Planning under Uncertainty and Incomplete Information, pages 33-42, August 2001.

[BLR00a]

Francesco Buccafurri, Nicola Leone, and Pasquale Rullo. Enhancing Disjunctive Datalog by Constraints. IEEE Transactions on Knowledge and Data Engineering, 12(5):845-860, 2000.

[BLR00b]

Francesco Buccafurri, Nicola Leone, and Pasquale Rullo. Enhancing Disjunctive Datalog by Constraints. IEEE Transactions on Knowledge and Data Engineering, 12(5):845-860, 2000.

[EFK+00]

Thomas Eiter, Wolfgang Faber, Christoph Koch, Nicola Leone, and Gerald Pfeifer. DLV -- A System for Declarative Problem Solving. In Chitta Baral and Miroslaw Truszczynski, editors, Proceedings of the 8th International Workshop on Non-Monotonic Reasoning (NMR'2000), Breckenridge, Colorado, USA, April 2000.

[EFL+00a]

Thomas Eiter, Wolfgang Faber, Nicola Leone, Gerald Pfeifer, and Axel Polleres. Planning under Incomplete Knowledge. In John Lloyd, Veronica Dahl, Ulrich Furbach, Manfred Kerber, Kung-Kiu Lau, Catuscia Palamidessi, Luís Moniz Pereira, Yehoshua Sagiv, and Peter J. Stuckey, editors, Computational Logic - CL 2000, First International Conference, Proceedings, volume 1861 of Lecture Notes in AI (LNAI), pages 807-821, London, UK, July 2000. Springer Verlag.

[EFL+00b]

Thomas Eiter, Wolfgang Faber, Nicola Leone, Gerald Pfeifer, and Axel Polleres. Using the dlv System for Planning and Diagnostic Reasoning. In François Bry, Ulrich Geske, and Dietmar Seipel, editors, Proceedings of the 14th Workshop on Logic Programming (WLP'99), pages 125-134. GMD -- Forschungszentrum Informationstechnik GmbH, Berlin, January 2000. ISSN 1435-2702.

[EFLP00]

Thomas Eiter, Wolfgang Faber, Nicola Leone, and Gerald Pfeifer. Declarative Problem-Solving Using the DLV System. In Jack Minker, editor, Logic-Based Artificial Intelligence, pages 79-103. Kluwer Academic Publishers, 2000.

[LPR00]

Nicola Leone, Simona Perri, and Pasquale Rullo. Local Search Techniques for Disjunctive Logic Programs. In Evelina Lamma and Paola Mello, editors, AI*IA'99: Advances in Artificial Intelligence, volume 1792 of Lecture Notes in AI (LNAI), pages 107-118. Springer, 2000.

[BFL99]

Francesco Buccafurri, Wolfgang Faber, and Nicola Leone. Disjunctive Logic Programs with Inheritance. In Danny De Schreye, editor, Proceedings of the 16th International Conference on Logic Programming (ICLP'99), pages 79-93, Las Cruces, New Mexico, USA, November 1999. The MIT Press.

[BLR99]

Francesco Buccafurri, Nicola Leone, and Pasquale Rullo. Semantics and Expressiveness of Disjunctive Ordered Logic. Annals of Mathematics and Artificial Intelligence, 25(3-4):311-337, November 1999.

[EFG+99]

Thomas Eiter, Wolfgang Faber, Georg Gottlob, Christoph Koch, Nicola Leone, Cristinel Mateis, Gerald Pfeifer, and Francesco Scarcello. The DLV System. In Jack Minker, editor, Workshop on Logic-Based Artificial Intelligence, Washington, DC, College Park, Maryland, June 1999. Computer Science Department, University of Maryland. Workshop Notes.

[EFLP99]

Thomas Eiter, Wolfgang Faber, Nicola Leone, and Gerald Pfeifer. The Diagnosis Frontend of the dlv System. AI Communications -- The European Journal on Artificial Intelligence, 12(1-2):99-111, 1999. (PostScript)

[FLMP99]

Wolfgang Faber, Nicola Leone, Cristinel Mateis, and Gerald Pfeifer. Using Database Optimization Techniques for Nonmonotonic Reasoning. In INAP Organizing Committee, editor, Proceedings of the 7th International Workshop on Deductive Databases and Logic Programming (DDLP'99), pages 135-139. Prolog Association of Japan, September 1999. (PostScript)

[FLP99a]

Wolfgang Faber, Nicola Leone, and Gerald Pfeifer. Computing Consistent Preferred Answer Sets. Technical Report DBAI-TR-99-28a, Institut für Informationssysteme, Technische Universität Wien, Austria, April 1999.

[FLP99b]

Wolfgang Faber, Nicola Leone, and Gerald Pfeifer. dlv: a DLP System for AI. In Evelina Lamma and Paola Mello, editors, Sixth Congress of the Italian Association for Artificial Intelligence (AIIA '99), pages 511-514, Bologna, Italy, September 1999. Pitagora Editrice Bologna.

[FLP99c]

Wolfgang Faber, Nicola Leone, and Gerald Pfeifer. Pushing Goal Derivation in DLP Computations. In Michael Gelfond, Nicola Leone, and Gerald Pfeifer, editors, Proceedings of the 5th International Conference on Logic Programming and Nonmonotonic Reasoning (LPNMR'99), volume 1730 of Lecture Notes in AI (LNAI), pages 177-191, El Paso, Texas, USA, December 1999. Springer Verlag.

[GLS99]

Georg Gottlob, Nicola Leone, and Francesco Scarcello. On the Complexity of some Inductive Logic Programming Problems. New Generation Computing, 17(1):53-77, 1999.

[KL99]

Christoph Koch and Nicola Leone. Stable Model Checking Made Easy. In Thomas Dean, editor, Proceedings of the Sixteenth International Joint Conference on Artificial Intelligence (IJCAI) 1999, pages 70-75, Stockholm, Sweden, August 1999. Morgan Kaufmann Publishers.

[LPR99]

Nicola Leone, Simona Perri, and Pasquale Rullo. Utilizzo di tecniche di AI per la Programmazione Logica Disgiuntiva. In Evelina Lamma and Paola Mello, editors, Sixth Congress of the Italian Association for Artificial Intelligence (AIIA '99), Bologna, Italy, September 1999. Pitagora Editrice Bologna.

[BFK+98]

Robert Bihlmeyer, Wolfgang Faber, Christoph Koch, Nicola Leone, Cristinel Mateis, and Gerald Pfeifer. dlv -- An Overview. In Uwe Egly and Hans Tompits, editors, Proceedings of the 13th Workshop on Logic Programming (WLP'98), pages 65-67, Vienna, Austria, October 1998.

[BLR98]

Francesco Buccafurri, Nicola Leone, and Pasquale Rullo. Disjunctive Ordered Logic: Semantics and Expressiveness. In Anthony G. Cohn, Lenhart K. Schubert, and Stuart C. Shapiro, editors, Proceedings Sixth International Conference on Principles of Knowledge Representation and Reasoning (KR'98), pages 418-429. Morgan Kaufmann Publishers, 1998.

[Cap98]

Antonella Capalbo. Estensione del linguaggio SQL con costrutti non deterministici. Master's thesis, D.E.I.S., Università degli Studi della Calabria, Rende (CS), Italy, 1998. Supported by Nicola Leone.

[EFLP98]

Thomas Eiter, Wolfgang Faber, Nicola Leone, and Gerald Pfeifer. The Diagnosis Frontend of the dlv System. Technical Report DBAI-TR-98-20, Institut für Informationssysteme, Technische Universität Wien, Austria, November 1998. Published in AICOM. (PostScript)

[ELM+98a]

Thomas Eiter, Nicola Leone, Cristinel Mateis, Gerald Pfeifer, and Francesco Scarcello. Progress Report on the Disjunctive Deductive Database System dlv. In Troels Andreasen, Henning Christiansen, and Henrik Legind Larsen, editors, Proceedings International Conference on Flexible Query Answering Systems (FQAS'98), volume 1495 of Lecture Notes in AI (LNAI), pages 148-163, Roskilde University, Denmark, May 1998. Springer. (PostScript)

[ELM+98b]

Thomas Eiter, Nicola Leone, Cristinel Mateis, Gerald Pfeifer, and Francesco Scarcello. The KR System dlv: Progress Report, Comparisons and Benchmarks. In Anthony G. Cohn, Lenhart K. Schubert, and Stuart C. Shapiro, editors, Proceedings Sixth International Conference on Principles of Knowledge Representation and Reasoning (KR'98), pages 406-417. Morgan Kaufmann Publishers, 1998. (PostScript)

[ELS98]

Thomas Eiter, Nicola Leone, and Domenico Saccá. Expressive Power and Complexity of Partial Models for Disjunctive Deductive Databases. Theoretical Computer Science, 206(1-2):181-218, October 1998. (PostScript)

[FLP98]

Wolfgang Faber, Nicola Leone, and Gerald Pfeifer. Representing School Timetabling in a Disjunctive Logic Programming Language. In Uwe Egly and Hans Tompits, editors, Proceedings of the 13th Workshop on Logic Programming (WLP'98), pages 43-52, Vienna, Austria, October 1998.

[BLR97a]

Francesco Buccafurri, Nicola Leone, and Pasquale Rullo. Adding Weak Constraints to Disjunctive Datalog. In Proceedings of the 1997 Joint Conference on Declarative Programming APPIA-GULP-PRODE'97, Grado, Italy, June 1997.

[BLR97b]

Francesco Buccafurri, Nicola Leone, and Pasquale Rullo. Strong and Weak Constraints in Disjunctive Datalog. In Jürgen Dix, Ulrich Furbach, and Anil Nerode, editors, Proceedings of the 4th International Conference on Logic Programming and Non-Monotonic Reasoning (LPNMR'97), volume 1265 of Lecture Notes in AI (LNAI), pages 2-17, Dagstuhl, Germany, July 1997. Springer Verlag.

[CEF+97]

Simona Citrigno, Thomas Eiter, Wolfgang Faber, Georg Gottlob, Christoph Koch, Nicola Leone, Cristinel Mateis, Gerald Pfeifer, and Francesco Scarcello. The dlv System: Model Generator and Application Frontends. In François Bry, Burkhard Freitag, and Dietmar Seipel, editors, Proceedings of the 12th Workshop on Logic Programming (WLP'97), Research Report PMS-FB10, pages 128-137, München, Germany, September 1997. LMU München.

[CLS97]

Marcello Crovara, Nicola Leone, and Domenico Saccà. Un'Estensione della Programmazione Logica per la Rappresentazione di Sistemi Dinamici. Rivista di Informatica, 27(2):67-103, July 1997.

[EGL97a]

Thomas Eiter, Georg Gottlob, and Nicola Leone. Abduction from Logic Programs: Semantics and Complexity. In Theoretical Computer Science [EGL97b], pages 129-177.

[EGL97b]

Thomas Eiter, Georg Gottlob, and Nicola Leone. Abduction from Logic Programs: Semantics and Complexity. Theoretical Computer Science, 189(1-2):129-177, December 1997.

[ELM+97a]

Thomas Eiter, Nicola Leone, Cristinel Mateis, Gerald Pfeifer, and Francesco Scarcello. A Deductive System for Nonmonotonic Reasoning. In Jürgen Dix and Ulrich Furbach and Anil Nerode, editor, Proceedings of the 4th International Conference on Logic Programming and Nonmonotonic Reasoning (LPNMR'97), volume 1265 of Lecture Notes in AI (LNAI), pages 363-374, Dagstuhl, Germany, July 1997. Springer.

[ELM+97b]

Thomas Eiter, Nicola Leone, Cristinel Mateis, Gerald Pfeifer, and Francesco Scarcello. Projektbericht: Ein Nichtmonotones Disjunktives Datenbanksystem. ÖGAI Journal (J. of the Austrian Society for AI), 16(2):6-11, October 1997. In German. English Title: Project Report: A Nonmonotonic Disjunctive Deductive Database System.

[ELM+97c]

Thomas Eiter, Nicola Leone, Cristinel Mateis, Gerald Pfeifer, and Francesco Scarcello. The Architecture of a Disjunctive Deductive Database System. In Moreno Falaschi, Marisa Navarro, and Alberto Policriti, editors, Proceedings Joint Conference on Declarative Programming (APPIA-GULP-PRODE '97), pages 141-151, June 1997.

[ELS97]

Thomas Eiter, Nicola Leone, and Domenico Saccà. On the Partial Semantics for Disjunctive Deductive Databases. Annals of Mathematics and Artificial Intelligence, 19(1-2):59-96, April 1997.

[GLS97]

Sergio Greco, Nicola Leone, and Francesco Scarcello. Disjunctive Datalog with Nested Rules. In Proceedings of the ILPS'97 International Workshop on Logic Programming and Knowledge Representation (LPKR'97), Port Jefferson, N.Y., October 1997.

[LRS97]

Nicola Leone, Pasquale Rullo, and Francesco Scarcello. Disjunctive Stable Models: Unfounded Sets, Fixpoint Semantics and Computation. Information and Computation, 135(2):69-112, June 1997. (PostScript)

[BLR96]

Francesco Buccafurri, Nicola Leone, and Pasquale Rullo. Stable Models and their Computation for Logic Programming with Inheritance and True Negation. Journal of Logic Programming, 27(1):5-43, 1996.

[FP96]

Wolfgang Faber and Gerald Pfeifer. DLV homepage, since 1996. url http://www.dlvsystem.com/.