******************************************************************** ELECTRONIC NEWSLETTER ON REASONING ABOUT ACTIONS AND CHANGE Issue 97036 Editor: Erik Sandewall 30.12.1997 Back issues available at http://www.ida.liu.se/ext/etai/actions/njl/ ******************************************************************** ********* TODAY ********* The second-last Newsletter issue for 1997 contains abstracts of three recent articles (not ETAI submitted) on reasoning about actions and change, and a comment that puts these articles in perspective. Tomorrow's Newsletter will contain a summary of the state of articles presently under review, and a concluding editorial statement that summarizes the experience of the ETAI and of the present Newsletter during the past year. ********* PUBLICATIONS ********* --- ARTICLES --- The following three articles from the Doherty group have been published recently, and describe how they deal with (in turn) concurrency, qualification, and ramification. In particular, these article provide the detailed answers to Vladimir Lifschitz's questions to Sandewall and Doherty, in an earlier issue of this Newsletter. The first two articles have been submitted for reviewing in another journal (not ETAI), and can therefore not be included among the articles presently being reviewed by ETAI. We have had some previous cases where the present Newsletter included references and links to current articles that are in the publication channel for elsewhere, for example the papers by Judea Pearl and his group (ENRAC 97002, 22.9.1997). We would like to encourage readers to make use of this possibility of making their current work known to the community. The third article mentioned below is a documentation of the details of the approach: precise definition of the logic, solutions for test examples, and so forth. This is the kind of material that is not traditionally published by our journals or conferences, but which is important for any detailed analysis of an approach, and for comparisons between approaches. It is therefore reference material in the strong sense of the word: appropriate to use as a reference in conventional articles, and in order to document the details of the method being proposed. Again, we welcome similar documentations from all our readers. ======================================================== | AUTHOR: Lars Karlsson and Joakim Gustafsson | TITLE: Reasoning about actions in a multi-agent environment | PAPER: http://www.ep.liu.se/ea/cis/1997/014/ | Published by Linköping University Electronic Press on 1997-11-14. ======================================================== Abstract: In this paper we present TAL-C, a logic of action and change for multi-agent environments which has a first-order semantics and proof theory. It is demonstrated how TAL-C can represent (cases of) a number of phenomena related to action concurrency: action duration, interference between one action's effects and another action's execution, bounds on concurrency, and conflicting, synergistic and cumulative effects of concurrent actions. A central idea is that most of the dynamics of the world is encoded in dependency laws relating to specific features instead of encoded directly in action laws. Thus, treatment of different types of interaction can be customized for specific features. ======================================================== | AUTHOR: Patrick Doherty and Jonas Kvarnström | TITLE: Tackling the Qualification Problem using Fluent | Dependency Constraints: Preliminary Report | PAPER: http://www.ep.liu.se/ea/cis/1997/016/ | Published by Linköping University Electronic Press on 1997-12-19. ======================================================== Abstract: Recently, a great deal of progress has been made using nonmonotonic temporal logics to formalize reasoning about action and change. In particular, much focus has been placed on the proper representation of non-deterministic actions and the indirect effects of actions. One popular approach to representing the indirect effects of actions has been via the use of *causal* rules which in a more general sense can be viewed as fluent dependency constraints. Although fluent dependency constraints have been used primarily under a loose causal interpretation, we show that when interpreted in a broader sense they provide a flexible means for dealing with a number of other representational problems such as the qualification problem and the ramification constraints as qualification constraints problem, in addition to the standard ramification problem. More importantly, the use of fluent dependency constraints for different purposes does not involve additions to the base nonmonotonic temporal logic, TAL, used here, but simply the addition of several macro operators to an action language used to represent action scenarios or narratives. The payoff is that TAL has already been shown to offer a robust approach to representing action scenarios which permit incomplete specifications of both state and the timing of actions, non-deterministic actions, actions with duration, concurrent actions, use of both boolean and non-boolean fluents, and solutions to the frame and ramification problems for a wide class of action scenarios. In addition, all circumscribed action scenarios in these classes and the more general class involving qualification considered in this paper can be shown to be reducible to the first-order case. Finally, a restricted entailment method for this new class of scenarios is fully implemented. In the paper, we present a challenge example which incorporates all these features, propose a distinction between *weak* and *strong* qualification with a representation of both, and provide a visualization of the preferred entailments using a research tool VITAL for querying and visualizing action scenarios. ======================================================== | AUTHOR: Patrick Doherty | TITLE: PMON+: A Fluent Logic for Action and Change: | Formal Specification, Version 1.0 | PAPER: http://www.ep.liu.se/ea/cis/1997/020/ | Published by Linköping University Electronic Press on 1997-12-19. ======================================================== Abstract: This report describes the current state of work with PMON, a logic for reasoning about actions and change, and its extensions. PMON has been assessed correct for the K-IA class using Sandewall's Features and Fluents framework which provides tools for assessing the correctness of logics of action and change. A syntactic characterization of PMON has previously been provided in terms of a circumscription axiom which is shown to be reducible to a first-order formula. This report introduces a number of new extensions which are also reducible and deal with ramification. This report is intended to provide a formal specification of the PMON family of logics and the surface language L(SD) used to represent action scenario descriptions. It should be considered a working draft. The title of the report has a version number because both the languages and logics are continually evolving. Since this document is intended as a formal specification which is used by our group as a reference for research and implementation, it is understandably brief as regards intuitions and applications of the language and logics defined. We do provide a set of benchmarks and comments concerning these which can serve as a means of comparing this formalism with others. The set of benchmarks is not complete and is only intended to provide representative examples of the expressivity and use of this particular family of logics. We describe its features and limitations in other publications by our group which can normally be found at http://www.ida.liu.se/labs/kplab/ ******************************************************************** This Newsletter is issued whenever there is new news, and is sent by automatic E-mail and without charge to a list of subscribers. To obtain or change a subscription, please send mail to the editor, erisa@ida.liu.se. Contributions are welcomed to the same address. Instructions for contributors and other additional information is found at: http://www.ida.liu.se/ext/etai/actions/njl/ ********************************************************************