Ajay Bansal

Automatic Composition of SemanticWeb Services

Service-oriented computing is gaining wider acceptance. For Web services to become practical, an infrastructure needs to be supported that allows users and applications to discover, deploy, compose and synthesize services automatically. For this automation to be effective, formal semantic descriptions of Web services should be available. In this paper we formally define the Web service discovery and composition problem and present an approach for automatic service discovery and composition based on semantic description of Web services. We also report on an implementation of a semantics-based automated service discovery and composition engine that we have developed. This engine employs a multi-step narrowing algorithm and is efficiently implemented using the constraint logic programming technology. The salient features of our engine are its scalability, i.e., its ability to handle very large service repositories, and its extremely efficient processing times for discovery and composition queries. We evaluate our engine for automated discovery and composition on repositories of different sizes and present the results.

Generalized Semantics-Based Service Composition

Service-oriented computing (SOC) has emerged as the eminent market environment for sharing and reusing service-centric capabilities. The underpinning for an organizations use of SOC techniques is the ability to discover and compose Web services. Although industry approaches to composition have a strong notion of business processes, these approaches largely use syntactic descriptions. As such composition is limited since the true functionality of ambiguous service operations cannot be inferred. Alternatively, academia uses semantic approaches to disambiguate services, but, at the same time, most of these approaches neglect the process rigor needed for complex compositions. In this paper we present a generalized semantics-based technique for automatic service composition that combines the rigor of process-oriented composition with the descriptiveness of semantics. Our generalized approach extends the common practice of linearly linked services by introducing the use of a conditional directed acyclic graph (DAG) where complex interactions, containing control flow, information flow and pre/post conditions, are effectively represented. Furthermore, the composition can be represented semantically as OWL-S documents. Our contributions are applied for automatic workflow generation in context of the currently important bioinformatics domain.

Coinductive logic programming and its applications

Coinduction has recently been introduced as a powerful technique for reasoning about unfounded sets, unbounded structures, and interactive computations. Where induction corresponds to least fixed point semantics, coinduction corresponds to greatest fixed point semantics. In this paper we discuss the introduction of coinduction into logic programming. We discuss applications of coinductive logic programming to verification and model checking, lazy evaluation, concurrent logic programming and non-monotonic reasoning.

Co-logic programming: extending logic programming with coinduction

In this paper we present the theory and practice of co-logic programming (co-LP for brevity), a paradigm that combines both inductive and coinductive logic programming. Co-LP is a natural generalization of logic programming and coinductive logic programming, which in turn generalizes other extensions of logic programming, such as infinite trees, lazy predicates, and concurrent communicating predicates. Co-LP has applications to rational trees, verifying infinitary properties, lazy evaluation, concurrent LP, model checking, bisimilarity proofs, etc.

WSC-2009: A Quality of Service-Oriented Web Services Challenge

With the growing acceptance of service-oriented computing, an emerging area of research is the investigation of technologies that will enable the discovery and composition of web services. The Web Services Challenge (WSC) is a forum where academic and industry researchers can share experiences of developing tools that automate the integration of web services. In the fifth year (i.e. WSC-09) of the Web Services Challenge, software platforms will address several new composition challenges. Requests and results will be transmitted within SOAP messages. Semantics will be represented as ontologies written in OWL, services will be represented in WSDL, and service orchestrations will be represented in WSBPEL. In addition, non-functional properties (Quality of Service) of a service will be represented using WSLA format.

Trust-based Dynamic Web service Composition using Social Network Analysis

With the increasing popularity of Web services and Service-Oriented Architecture, we need sophisticated infrastructure to discover and compose Web services. Dynamic Web service Composition will gain wider acceptance only when the users know that the solutions obtained are comprised of trust-worthy services. In this paper, we present a framework for a Trust-based Dynamic Web service Composition that not only uses functional and non-functional attributes provided by the Web service description document but also filters and ranks solutions based on their trust rating. With the increasing popularity of Web-based Social Networks like Linkedin, Facebook, Orkut, and Twitter, there is great potential in determining the trust rating of a particular service provider or service provider organization using Social Network Analysis. We present a technique to calculate a trust rating per service using Centrality measure of Social Networks. We use this rating to further filter composition results to produce solutions that are comprised of services provided by trusted providers.

A universal service-semantics description language

For Web-services to become practical, an infrastructure needs to be supported that allows users and applications to discover, deploy, compose, and synthesize services automatically. This automation can take place only if a formal description of the Web-services is available. In this paper we present an infrastructure using USDL (universal service-semantics description language), a language for formally describing the semantics of Web-services. USDL is based on the Web Ontology Language (OWL) and employs WordNet as a common basis for understanding the meaning of services. USDL can be regarded as formal service documentation that will allow sophisticated conceptual modeling and searching of available Web-services, automated service composition, and other forms of automated service integration. A theory of safe service substitution for USDL is presented and proved sound and complete. The rationale behind the design of USDL along with its formal specification in OWL is presented with examples. We also compare USDL with other approaches like OWL-S and WSML and show that USDL is complementary to these approaches.

WSC-08: Continuing the Web Services Challenge

The capabilities of organizations can be openly exposed, easily searched and discovered, and made readily-accessible to humans and particularly to machines, using service-oriented computing approaches. Artificial intelligence and software engineering researchers alike are tantalized by the promise of ubiquitously discovering and incorporating services into their own business processes (i.e. composition and orchestration). With growing acceptance of service-oriented computing, an emerging area of research is the investigation of technologies that will enable the discovery and composition of web services. The Web Services Challenge (WSC) is a forum where academic and industry researchers can share experiences of developing tools that automate the integration of Web services. In the fourth year (i.e. WSC-08) of the Web Services Challenge, software platforms will address several new composition challenges. Requests and results will be transmitted within SOAP messages. In addition, semantics will be represented as ontologies written in OWL, services will be represented in WSDL, and service orchestrations will be represented in WS-BPEL.

A Universal Service Description Language

To fully utilize Web-services, users and applications should be able to discover, deploy, compose and synthesize services automatically. This automation can take place only if a formal semantic description of the Web-services is available. In this paper we present a markup language called USDL (Universal Service Description Language), for formally describing the semantics of Web-services.

Goal-directed execution of answer set programs

Answer Set Programming (ASP) represents an elegant way of introducing non-monotonic reasoning into logic programming. ASP has gained popularity due to its applications to planning, default reasoning and other areas of AI. However, none of the approaches and current implementations for ASP are goal-directed. In this paper we present a technique based coinduction that can be employed to design SLD resolution-style, goal-directed methods for executing answer set programs. We also discuss advantages and applications of such goal-directed execution of answer set programs, and report results from our implementation.