1. The Semantic Web Service Shuying Wang 2004.02

2. Outline Semantic Web vision Core technologies XML, RDF, Ontology, Agent… Web services DAML-S

3. What is the Semantic Web? A vision of possibilities “ The Semantic Web is an extension of the current web in which information is given well-defined meaning, better enabling computers and people to work in cooperation. ”

4. The goal of Semantic Web In the Semantic Web we will need: Machines talking to machines – semantics need to be unambiguously declared Joined-up data – enabling complex tasks based on information from various sources Wide scope – from, say, home to government to commerce Trust – both in data and who is saying it This is not going to be easily achieved

5. Layers of the Semantic Web

6. Semantic Web Architecture

7. Core technologies eXtensible Markup Language (XML) Resource Description Framework (RDF) Ontologies Software agents

8. Uniform Resource Identifier (URI) A URI with a fragment identifier is taken to denote an object described in the knowledge base identified by the base URI. The URI is the foundation of the Web A URI provides an identifier for a resource Everyone can create a URI We use URI to solve the ambiguous name. The names we use are web addresses

9. XML (eXtensible Markup Language) Standard designed to transmit structured data to Web applications Describes structure & content Provides syntactic interoperability XML namespaces qualify element names uniquely on the Web in order to avoid conflicts between elements with the same name

10. Metadata in XML A sentence: “I just got a new pet dog.” XML: I just got a new pet dog.

11. RDF( Resource Description Framework ) RDF--the Resource Description Framework--is a universal format for data on the Web. Using a simple relational model, it allows structured and semi- structured data to be mixed, exported and shared across different applications. Where XML provides interoperability within one application (e.g. bank statements) using a given schema, RDF provides interoperability across applications (eg import your bank statements into your calendar).Resource Description Framework interoperability of data machine understandable semantics for metadata better precision in resource discovery than full text search future-proofing applications as schemas evolveschemas

12. RDF Data Model <rdf:Description rdf:about="http://doc" dc:creator= "Wang" dc:title= “ page.html" dc:description= “ Wang's ramblings about his summer vacation. “ dc:date= “ 2004-02-10" /> Resource Value PropertyType Property RDF Data Model Wang written by 10-Feb-04 on page.html Resourcehas propertyvalue Page.htmlwritten-byWang Known as triples or tuples

13. Ontologies An ontology formally defines a common set of terms that are used to describe and represent a domain (e.g., librarianship, medicine, etc.) Ontologies include computer-usable definitions of basic concepts in the domain and the relationships among them Ontologies are usually expressed in a logic- based language

14. Ontologies XML DTDs: Document Type Definition Define structure: Car application contains a price (integer), description and colour XML Schemas: Allows richer definitions Define structure: Car application contains a price (+ve integer between 1 and 20,000), description and colour (taken from fixed vocabulary) Ontologies: Define relationships Builds on AI techniques

15. Three Levels of generality in a domain ontology Foundational ontology Core ontology Specific Domain ontology

16. Web Services The web is organized around URIs, HTML, and HTTP. URIs provide defined ids to refer to elements on the web, HTML provides a standardized way to describe document structures (allowing browsers to render information for the human reader), and HTTP defines a protocol to retrieve information from the web. Not surprisingly, web services require a similar infrastructure around UDDI, WSDL, and SOAP. UDDI HTML HTTP URI WSDL SOAP

17. Web Services UDDI provides a mechanism for clients to find web services. A UDDI registry is similar to a CORBA trader, or it can be thought of as a DNS service for business applications. WSDL defines services as collections of network endpoints or ports. A port is defined by associating a network address with a binding; a collection of ports define a service. SOAP is a message layout specification that defines a uniform way of passing XML-encoded data. It also defines a way to bind HTTP as the underlying communication protocol. SOAP is basically a technology to allow for “ RPC over the web ”.

18. Semantic Web Services The Semantic Web services vision is to describe Web services ’ capabilities and content in an unambiguous, computer-interpretable language and improve the quality and robustness of existing tasks, such as Web service discovery and invocation. Semantic Web Services will also enable a broad range of new automation tasks that human previously formed, including automated composition, interoperation, execution monitoring, and recovery.

19. DAML-S(DARPA Agent Markup Language) The Semantic Web Services arm of the DAML program is developing an OWL-based Web Service Ontology, OWL-S (formerly DAML-S), as well as supporting tools and agent technology to enable automation of services on the Semantic Web. OWL-S supplies Web service providers with a core set of markup language constructs for describing the properties and capabilities of their Web services in unambiguous, computer-interpretable form. OWL-S markup of Web services will facilitate the automation of Web service tasks including automated Web service discovery, execution, interoperation, composition and execution monitoring.

20. DAML-S Service Service Model Service Profile Resources Service Grounding provides presents Described by supports What the service does How it works How to access it

21. Software agents “...programs that collect Web content from diverse sources, process the information and exchange the results with other programs” Software agents will become effective as more well-defined content & other agents become available

22. Resources Semantic Web, W3C Semantic Web Road map, Tim Berners-Lee The Semantic Web, Scientific American The Semantic Web Community Portal, The Semantic Web: A Primer DAML All found using Google to search for “semantic Web”