www.computer.org/intelligent Semantic Web Services, Part 2 David Martin, John Domingue, Amit Sheth, Steve Battle, Katia Sycara, and Dieter Fensel Vol. 22, No. 6 November/December 2007 This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder. © 2007 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. For more information, please see www.ieee.org/portal/pages/about/documentation/copyright/polilink.html. Trends & Controversies Semantic Web Services, Part 2 David Martin, SRI International John Domingue, Knowledge Media Institute, Open University taken the first concrete steps toward building a SWS- n part 2 of this Trends & Controversies installment, we continue based solution: the W3C proposed recommendation exploring the state of the art, current practices, and future direc- SAWSDL (www.w3.org/2002/ws/sawsdl), its associated I tions for Semantic Web services. SWS aims to bring Semantic Web tools and use cases, and initial applications.1 Where do we technology—for representing, sharing, and reasoning about know- go from here? The researchers among us might be fully ledge—to bear in Web service contexts. The objective is to enable a convinced of the importance and benefit of adding seman- fuller, more flexible automation of service provision and use and the tics to Web services and impatient to see their research construction of more powerful tools and methodologies for working translated into technologies and adapted for real use. How- with services. For an overview of SWS, please see our introduction to ever, I believe we might need to do a lot more work before part 1 in the September/October 2007 issue. That introduction also we see substantial adoption of SWS technologies. includes references for major SWS initiatives, such as SAWSDL, OWL-S. First, we must be patient. Both Web services and the WSMO, SWSF, and the Internet Reasoning Service. Part 1 also includes Semantic Web are prerequisites for SWS, at least in the essays by Michael L. Brodie and Frank Leymann that discuss service tech- form in which SAWSDL or its extensions could evolve. Des- nology needs from a long-term industry perspective. In this issue, we pite a clear uptick in adoption of Web services by industry, conclude with four more essays. initial success stories, and early adoption of Semantic Web The first two essays are primarily concerned with nearer-term direc- technologies,2 broad acceptance and adoption could take tions—steps that will let us build out from the current state of the art another three years or so. For the Web services part, the rea- toward greater adoption and applicability of SWS approaches. Amit son is the complexity and confusion resulting from WS-* Sheth lays out a near-term roadmap of steps that will be essential for specifications, some of which (such as security and policy/ industry acceptance of SWS approaches, starting from SAWSDL and cur- agreement) are critical and either not yet mature or yet to be rent industry practice. (See the “Frequently Used Acronyms” sidebar for broadly adopted. For the Semantic Web, the challenges are explanations of SAWDSL and other terms.) Among other things, he coun- to convince practitioners sels that essential steps are required to make SWS approaches suffi- ciently accessible and economically attractive to industry. Steve Battle • that ontologies can be and have been built and are starts with an analysis of OWL-S’s strengths and limitations. He then manageable, discusses the necessary evolution of business ontologies for SWS. Along • that we can do much with limited semantics and with- with the evolution of business practices, this will allow for Web services out becoming experts in description logic, and SWS approaches to come together. • that we don’t need a single ontology for everything and The final two essays put forward longer-term agendas for the evolu- we know how to work reasonably well in a multi-ontology tion of SWS. Katia Sycara argues that SWS could benefit from decoup- environment, and ling itself from the basic stack of Web service standards rather than fol- • that technology is ready for building robust applications. lowing a more incremental trajectory tied to their evolution. She also identifies two important opportunities in which this strategy could pay We might also have to wait out the current Web 2.0 eu- off. Dieter Fensel takes a broad perspective, arguing that the character- phoria, bordering on infatuation. Clearly, Web 2.0 is se- istics of Internet-scale service usage, and problem solving in general, call ductive, easy to use and adopt, and highly valuable for for an entirely new conceptualization of some of the core challenges of some purposes, but it isn’t a solution to all problems and computer science for the 21st century. requirements. Technologies such as SWS won’t get at- —David Martin and John Domingue tention until there is a broader realization of what prob- lems Web 2.0 can’t solve and why Web 3.0 (the new code for Semantic Web technologies-enabled Web) is needed. Beyond SAWSDL: A Game Plan for Broader Second, we must do a better job of understanding, ex- Adoption of Semantic Web Services plaining, and managing the complexity of using SWS. Take, Amit Sheth, Kno.e.sis Center, Wright State University for example, the SWS Challenge (http://sws-challenge.org), in which six teams of researchers have implemented or tried After a flurry of research led by the OWL-S, WSMO, to implement a solution to a realistic but relatively simple SWSF, and WSDL-S groups, the SWS community has application using widely different approaches, formalisms, 8 1541-1672/07/$25.00 © 2007 IEEE IEEE INTELLIGENT SYSTEMS Published by the IEEE Computer Society techniques, and technologies. Only one team input of the subsequent used SAWSDL. In SAWSDL’s defense, this chal- task or tasks). Clearly Frequently Used Acronyms lenge started well before it became a pro- demonstrating how posed recommendation. But a WSDL-S sub- SWS can ease this or BPEL: Business Process Execution Language mission to W3C (see www.w3.org/Submission/ equally vexing problems DAML-S: DARPA Agent Markup Language for Services WSDL-S), which became the starting point that process developers OWL: Web Ontology Language OWL-S: Web Ontology Language for Services for W3C’s work toward SAWSDL, has contin- face will be important. ued at the same time. More important, the Today’s enterprise ser- RDF: Resource Description Framework exercise, which has already involved four vice bus, application RDFS: RDF Schema meetings and spanned well over a year, server, and service- SAWSDL: Semantic Annotations for WSDL shows how complex the challenges are, es- based middleware ven- SWSF: Semantic Web Services Framework pecially when the problem involves legacy dors claim to solve the SOA: Service-Oriented Architecture systems or interfaces for preexisting ser- data-mediation problem UDDI: Universal Description Discovery and Integration vices. Lessons from this exercise lead to using XSLT (Extensible WSDL: Web Services Description Language two observations related to technical issues Style Sheet Language WSMO: Web Services Modeling Ontology (tools and methodologies) and business Transformation)-based issues (ROI). transformation. Al- Before practitioners (developers and real- though this addresses numerous basic • Supporting precondition and effects in word users) will embrace SWS, they must problems, as my student Karthik Goma- SAWSDL. OWL-S and others have noted have robust tools as well as methodologies dam put it, “the idea of mediating at the this need for some time, and more re- to streamline all aspects of managing the level of instance or between two fixed cently clear use cases have emphasized SWS life cycle, including annotation, publi- schemas is hackneyed.” To accelerate this a need for such support. cation, discovery, data mediation, composi- technology’s adoption, we must focus on • Semantic annotation of policy descrip- tion or configuration, orchestration, and exe- issues such as data and process mediation tions. From a business perspective, this cution. In the context of SAWSDL, initial where using semantics will likely provide will be very important, especially to sup- versions of most of these have been devel- solid cases of ROI. Efforts that use semantic port nonfunctional or quality-of-service oped—some by the LSDIS (Large Scale and ontological approaches for interoperabil- requirements. Distributed Information Systems) lab (see ity and data mediation3 will need to be put www.iswc2006.semanticweb.org/projects/ side by side with current nonsemantic ap- In addition, we intend to collaborate meteor-s/SAWSDL), Kno.e.sis Center proaches to drive the point home. with others who are developing an on- (see http://knoesis.wright.edu/research/ Finally, although early examples of real- tology for SWS, which I believe will build webservices), IBM (see www.alphaworks. world SAWSDL-based services already exist on work being done in the WSMO and ibm.com/tech/wssem), and others. But these (for example, see http://glycomics.ccrc.uga. OWL-S groups. On a more strategic and tools must be robust and in a form that devel- edu/stargate/web_services.jsp), we will need longer-term path, we hope to continue to opers find attractive to learn and use.