Zeki Bayram

XSLT version 2.0 is turing-complete: a purely transformation based proof

XSLT version 2.0 has the full power of a Turing machine, i.e. it is “Turing-complete.” We show this is so by implementing a universal Turing machine emulator stylesheet in XSLT. We use only the constructs available in the official XSLT version 2.0 recommendation of the World Wide Web Consortium. Furthermore, we do not resort to string functions (which are also available in XSLT) but rather rely on the innate transformational capabilities of XSLT.

A Novel Concise Specification and Efficient F-Logic Based Matching of Semantic Web Services in Flora-2

We propose a novel concise specification of semantic web services conforming to the WSMO standard using the Flora-2 language, as well as a precise logical definition of what it means for a goal to match a web service. Our innovative usage of Flora-2 allows very short but expressive descriptions of both goals and web service capabilities, which are then used by a matching engine to discover which web services can satisfy a given goal. The matching engine, using the meta-level F-logic inferencing capabilities of the underlying Flora-2 reasoner, is very efficient and has a very concise definition itself.

Semantic Web Services for University Course Registration

Semantic web services, with proper security procedures, have the potential to open up the computing infrastructure of an organization for smooth integration with external applications in a very controlled way, and at a very fine level of granularity. Furthermore, the process of using the provided functionality, consisting of discovery, invocation and execution of web services may be automated to a large extent. In this paper, we show how semantic web services and service-oriented computing can facilitate this integration in the education domain. Specifically, we use the Rule variant of Web Services Modeling Language WSML to semantically specify the functionality of web services for on-line course registration, a goal for consuming the provided functionality, as well as the ontologies needed for a shared terminology between the service andi??goal.

XLambda: A functional programming language with XML syntax

We describe XLambda, a functional language with XML syntax, and its processor which is implemented fully and completely in XSLT. XLambda has all the basic features of a functional language, such as defining named functions, operations on numbers, passing functions as parameters, constructing arbitrary data structures etc. What sets XLambda apart from the rest of the functional languages is not its feature set though, but rather its syntax and processor which is implemented as an XSLT stylesheet. Since most Web browsers have XSLT processors already built in, XLambda has the potential to be used as a scripting language in Browsers, much in the same way as JavaScript, among other possibilities.

Distance education using XML technology

Distance education is an instructional delivery system that connects learners with educational resources. In this paper, we report a system that realizes distance education by using XML technology. The system provides a Web interface to students who get course materials and take tests online using their browser. At the same time, it provides tools for instructors to design course materials and exams on their local machine and upload the materials to the server as XML documents.

An Improved Abstract State Machine Based Choreography Specification and Execution Algorithm for Semantic Web Services

We identify significant weaknesses in the original Abstract State Machine (ASM) based choreography algorithm of Web Service Modeling Ontology (WSMO), which make it impractical for use in semantic web service choreography engines. We present an improved algorithm which rectifies the weaknesses of the original algorithm, as well as a practical, fully functional choreography engine implementation in Flora-2 based on the improved algorithm. Our improvements to the choreography algorithm include (i) the linking of the initial state of the ASM to the precondition of the goal, (ii) the introduction of the concept of a final state in the execution of the ASM and its linking to the postcondition of the goal, and (iii) modification to the execution of the ASM so that it stops when the final state condition is satisfied by the current configuration of the machine. Our choreography engine takes as input semantic web service specifications written in the Flora-2 dialect of F-logic. Furthermore, we prove the equivalence of ASMs (evolving algebras) and evolving ontologies in the sense that one can simulate the other, a first in literature. Finally, we present a visual editor which facilitates the design and deployment of our F-logic based web service and goal specifications.

A Critical Evaluation of Web Service Modeling Ontology and Web Service Modeling Language

Web Service Modeling Language (WSML), based on the Web Service Modeling Ontology (WSMO), is a large and highly complex language designed for the specification of semantic web services. It has different variants based on logical formalisms, such as Description Logics, First-Order Logic and Logic Programming. We perform an in-depth study of both WSMO and WSML, critically evaluating them by identifying their strong points and areas in which improvement would be beneficial. Our studies show that in spite of all the features WSMO and WSML support, their sheer size and complexity are major weaknesses, and there are other areas in which important deficiencies exist as well. We point out those discovered deficiencies, and propose remedies for them, laying the foundation for a more tractable and useful formalism for specifying semantic web services.

Unifying F-logic molecules: a rectification to the original unification algorithm

The original unification algorithm for F-Logic molecules presented by Kifer et al. 1995, contains a mistake. We identify the mistake and demonstrate it through two examples, suggest a solution to the problem in the original algorithm and prove that the resulting algorithm correctly unifies F-Logic molecules.

Prefiltering strategy to improve performance of semantic Web service discovery

Discovery of semantic Web services is a heavyweight task when the number of Web services or the complexity of ontologies increases. In this paper, we present a new logical discovery framework based on semantic description of the capability of Web services and user goals using F-logic. Our framework tackles the scalability problem and improves discovery performance by adding two prefiltering stages to the discovery engine. The first stage is based on ontology comparison of user request and Web service categories. In the second stage, yet more Web services are eliminated based upon a decomposition and analysis of concept and instance attributes used in Web service capabilities and the requested capabilities of the client, resulting in a much smaller pool of Web services that need to be matched against the client request. Our prefiltering approach is evaluated using a new Web service repository, called WSMO-FL test collection.The recall rate of the filtering process is 100% by design, since no relevant Web services are ever eliminated by the two prefiltering stages, and experimental results show that the precision rate is more than 53%.

An investigation of the course-section assignment problem

We investigate the problem of enumerating schedules, consisting of course-section assignments, in increasing order of the number of conflicts they contain. We define the problem formally, and then present an algorithm that systematically enumerates solutions for it. The algorithm uses backtracking to perform a depth-first search of the implicit search space defined by the problem, pruning the search space when possible. We derive a mathematical formula for the algorithm’s average-case time complexity using a probabilistic approach, and also give a brief overview of its implementation in a WEB application.