Browsing by Subject "Logic Programming"

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    Abstract metaprolog engine
    (Elsevier, 1998) Cicekli, I.
    A compiler-based meta-level system for MetaProlog language is presented. Since MetaProlog is a meta-level extension of Prolog, the Warren Abstract Machine (WAM) is extended to get an efficient implementation of meta-level facilities; this extension is called the Abstract MetaProlog Engine (AMPE). Since theories and proofs are main meta-level objects in MetaProlog, we discuss their representations and implementations in detail. First, we describe how to efficiently represent theories and derivability relations. At the same time, we present the core part of the AMPE, which supports multiple theories and a fast context switching among theories in the MetaProlog system. Then we describe how to compute proofs, how to shrink the search space of a goal using partially instantiated proofs, and how to represent other control knowledge in a WAM-based system. In addition to computing proofs that are just success branches of search trees, fail branches can also be computed and used in the reasoning process.
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    An intelligent backtracking schema in a logic programming environment
    (ACM, 1997) Cicekli, I.
    We present a new method to represent variable bindings in the Warren Abstract Machine (WAM), so that the ages of variable bindings can be easily found using this new representation in our intelligent backtracking schema. The age of a variable bound to a non-variable term is the youngest choice point such that backtracking to that choice point can make that variable an unbound variable again. The procedure backtracking point is the choice point of the procedure currently being executed or the choice point of its first ancestor having a choice point. Variable ages and procedure backtracking points are used in the process of figuring out backtracking points in our intelligent backtracking schema. Our intelligent backtracking schema performs much better than the results of other intelligent backtracking methods in the literature for deterministic programs, and its performance for non-deterministic programs are comparable with their results.
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    A logic programming framework for modelling temporal objects
    (IEEE, 1996-10) Kesim, N.; Sergot, M.
    We present a general approach for modeling temporal aspects of objects in a logic programming framework. Change is formulated in the context of a database which stores explicitly a record of all changes that have occurred to objects and thus (implicitly) all states of objects in the database. A snapshot of the database at any given time is an object-oriented database, in the sense that it supports an object-based data model. An object is viewed as a collection of simple atomic formulas, with support for an explicit notion of object identity, classes and inheritance. The event calculus is a treatment of time and change in first-order classical logic augmented with negation as failure. The paper develops a variant of the event calculus for representing changes to objects, including change in internal state of objects, creation and deletion of objects, and mutation of objects over time. The concluding sections present two natural and straightforward extensions, to deal with versioning of objects and schema evolution, and a sketch of implementation strategies for practical application to temporal object-oriented databases.
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    Metadata-based modeling of information resources on the web
    (Wiley, 2004) Özel, S. A.; Altingövde, S.; Ulusoy, Özgür; Özsoyoǧlu G.; Özsoyoǧlu, Z. M.
    This paper deals with the problem of modeling Web information resources using expert knowledge and personalized user information for improved Web searching capabilities. We propose a "Web information space" model, which is composed of Web-based information resources (HTML/XML [Hypertext Markup Language/Extensible Markup Language] documents on the Web), expert advice repositories (domain-expert-specified meta-data for information resources), and personalized information about users (captured as user profiles that indicates users' preferences about experts as well as users' knowledge about topics). Expert advice, the heart of the Web information space model, is specified using topics and relationships among topics (called metalinks), along the lines of the recently proposed topic maps. Topics and metalinks constitute metadata that describe the contents of the underlying HTML/XML Web resources. The metadata specification process is semiautomated, and it exploits XML DTDs (Document Type Definition) to allow domain-expert guided mapping of DTD elements to topics and metalinks. The expert advice is stored in an object-relational database management systems (DBMS). To demonstrate the practicality and usability of the proposed Web information space model, we created a prototype expert advice repository of more than one million topics/metalinks for DBLP (Database and Logic Programming) Bibliography data set. We also present a query interface that provides sophisticated querying facilities for DBLP Bibliography resources using the expert advice repository.
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    A Parallel Prolog emulator
    (1988) Gürsoy, Attila
    There are various parallel Prolog execution models proposed so far. In this study, an emulator has been developed to test the execution model PPEM. The emulator is used to collect data to evaluate the performance of the model. The underlying architecture is assumed to be a tightly coupled multiprocessor system. Some implementation difficulties faced, which are not apparent in the definition of PPEM are discussed, and performance results are presented.
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    Situated nonmonotonic temporal reasoning with BABY-SIT
    (IOS Press, 1997) Tın, E.; Akman, V.
    After a review of situation theory and previous attempts at 'computational' situation theory, we present a new programming environment, BABY-SIT, which is based on situation theory. We then demonstrate how problems requiring formal temporal reasoning can be solved in this framework. Specifically, the Yale Shooting Problem, which is commonly regarded as a canonical problem for nonmonotonic temporal reasoning, is implemented in BABY-SIT using Yoav Shoham's causal theories.
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    Using criticalities as a heuristic for Answer Set Programming
    (Springer, Berlin, Heidelberg, 2004) Sabuncu, O.; Alpaslan, F. N.; Akman, Varol
    Answer Set Programming is a new paradigm based on logic programming. The main component of answer set programming is a system that finds the answer sets of logic programs. Generally, systems utilize some heuristics to choose new literals at the choice points. The heuristic used in this process is one of the key factors for the performance of the system. A new heuristic for answer set programming has been developed. This heuristic is inspired by hierarchical planning. The notion of criticality, which was introduced for generating abstraction hierarchies in hierarchical planning, is used in this heuristic. The resulting system (CSMODELS) uses this new heuristic and is based on the system SMODELS. The experimental results show that this new heuristic is promising for answer set programming. CSMODELS generally takes less time than SMODELS to find an answer set.