CBSE and Service Oriented Computing Simela Topouzidou Thomi Pilioura Stephen Hall Cyprus Workshop 25-26th September 2003

2 Why discuss Service Oriented Computing? n This is a CBSE workshop! n Service Oriented Computing and Web Services influencing the development of software systems n Changing the way components are delivered n Cannot be ignored (CBDi, primarily discussing services) n Service Based Software Engineering is an evolution on CBSE n Challenges in CBSE are brought forward into SBSE (possibly magnified)

Cyprus Workshop 25-26th September What is Service Oriented Computing (SOC)? n New development paradigm based upon Services within an extended Service Oriented Architecture n Services are a collection of operations package as an entity that is self describing and is published for use with other software systems n Web services are instances of services that are identified by a URI and are described and communicate using open standards n Web Services are important to SOC as they offer interoperability n Services are deemed to be loosely coupled because they tolerate extension without proprietary lock-in and do not result in fixed connection points (dynamic binding)

Cyprus Workshop 25-26th September (Extended) SOA Model n SOA model involves three roles, consumer, provider and broker (aggregator) n The tasks within the basic model are represented by standards such as SOAP, WSDL and UDDI n Extended model includes composition of basic services, and top level management services Figure from [Service-Oriented Computing, M.P. Papazoglou and D. Georgakopoulos]

Cyprus Workshop 25-26th September Web Service Standards n WSDL, SOAP and UDDI are accepted as the standards for web services in the SOA model n There is less consensus on standards higher up the extended SOA model, there is also gaps in the technology that enable implementation of these standards n Standards organizations include W3C (WSDL and SOAP) and OASIS (UDDI) n EbXML is a competing set of standards to web services for business oriented transactions that currently has greater coverage in terms of specifications than web services

Cyprus Workshop 25-26th September Web Services Stack n Often shown as extension to the OSI 7 Layer model n Some “standards” sit on the stack l WSIL - Inspection language used to aggregate service descriptions to facilitate registries l Composition - WSFL, WSCL, XLANG, BPML, BPEL4WS n Other “standards” sit vertically throughout l WS-Security l WS-Interoperation (not a technology) l WS-Transactions HTTP/TCP SOAP WSDL UDDI BPEL4WS Network XML based Messaging Service Description Service Publication Service Discovery Service Composition Security Management Quality of Service

Cyprus Workshop 25-26th September SOA Middleware Platforms n So far we have only discussed the models and the standards behind the service oriented architecture n Web services are supported by most imperative languages n Key platforms - Microsoft.NET and J2EE based platforms such as IBM Websphere, Apache Axis, Sun One, and others. n All platforms support the base standards but often provide proprietary solutions to higher level specifications. For example the BPEL4WS engine is only available though IBM

Cyprus Workshop 25-26th September Contexts for Service Oriented Computing n Enterprise Wide (intra enterprise) l Where we are now l Same environment as distributed components l Service Oriented Architecture used to expose components to aid interoperability n Business 2 Business (cross enterprise) l The aim of Service Oriented Computing l Developers no longer have autonomy over the whole system l Presents a series of “Context Horizons”, new challenges

Cyprus Workshop 25-26th September Challenges for SOC in cross enterprise n Trust n Expressing/Matching Quality of Service l Security l Reliability/Availability/Performance n Expressing/Matching Service Capability l Semantics l Formal Methods n Expressing/Matching Behavior l Workflows n Enforcement l Contracts s Service Level Agreements s Negotiation l Metering

Cyprus Workshop 25-26th September A CBSE Approach n Can the CBSE process be used as a basis for engineering services in a cross enterprise environment. n Development for reuse l Component developers become Service Providers (More Roles) l Providers are responsible for hardware, OS and middleware have to ensure levels of quality of service, including security, reliability, performance n Development with reuse l Application developers become Service consumers l Discovery & Verification of online services is difficult placing a dependency on trust l Developers no longer have autonomy over the middleware/OS/hardware that services

Cyprus Workshop 25-26th September Related Paradigms n GRID computing l E-Science field l Open Grid Services Architecture (Globus 3.0 Toolkit) l Is extension to Service Oriented Architecture with lifetime management, state data, and notification capabilities n Semantic Web l Leading towards Agent based Computing l Ontology based languages such as OWL, DAML-S n Peer 2 Peer Networks

Cyprus Workshop 25-26th September Summary n Service Oriented Computing primarily driven by web services will promise intra and cross-enterprise systems n There are large gaps in the standards/technology beyond the base of SOA SOAP, WSDL, and UDDI n CBSE may be an appropriate starting point for a service based engineering approach SOC n Problem of discovery/verification of services magnifies the requirements for successful expression/matching of QoS, service capability, behavior and places a greater emphasis on trust

Cyprus Workshop 25-26th September Discussion ConceptService Oriented Computing, Service, QoS, Semantics, Composition ProcessService Based Software Engineering Process as extension to CBSE RolesService Consumer, Provider, Broker (Aggregator) BusinessMarket places for services ProductTrust, Security, other ilities, Behaviour, Capability TechnologyStandards SOAP, WSDL, UDDI. Platforms.NET. Off-the-shelfService Discovery / Matching Related ParadigmsCBSE Grid Computing Semantic Web P2P