CBSE and Service Oriented Computing

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

2. Why discuss Service Oriented Computing? • This is a CBSE workshop! • Service Oriented Computing and Web Services influencing the development of software systems • Changing the way components are delivered • Cannot be ignored (CBDi, primarily discussing services) • Service Based Software Engineering is an evolution on CBSE • Challenges in CBSE are brought forward into SBSE (possibly magnified) Cyprus Workshop 25-26th September 2003

3. What is Service Oriented Computing (SOC)? • New development paradigm based upon Services within an extended Service Oriented Architecture • Services are a collection of operations package as an entity that is self describing and is published for use with other software systems • Web services are instances of services that are identified by a URI and are described and communicate using open standards • Web Services are important to SOC as they offer interoperability • 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 2003

4. (Extended) SOA Model • SOA model involves three roles, consumer, provider and broker (aggregator) • The tasks within the basic model are represented by standards such as SOAP, WSDL and UDDI • 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 2003

5. Web Service Standards • WSDL, SOAP and UDDI are accepted as the standards for web services in the SOA model • 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 • Standards organizations include W3C (WSDL and SOAP) and OASIS (UDDI) • 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 2003

6. Service Composition BPEL4WS UDDI Service Discovery UDDI Service Publication Security Management Quality of Service Service Description WSDL XML based Messaging SOAP Network HTTP/TCP Web Services Stack • Often shown as extension to the OSI 7 Layer model • Some “standards” sit on the stack • WSIL - Inspection language used to aggregate service descriptions to facilitate registries • Composition - WSFL, WSCL, XLANG, BPML, BPEL4WS • Other “standards” sit vertically throughout • WS-Security • WS-Interoperation (not a technology) • WS-Transactions Cyprus Workshop 25-26th September 2003

7. SOA Middleware Platforms • So far we have only discussed the models and the standards behind the service oriented architecture • Web services are supported by most imperative languages • Key platforms - Microsoft .NET and J2EE based platforms such as IBM Websphere, Apache Axis, Sun One, and others. • 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 2003

8. Contexts for Service Oriented Computing • Enterprise Wide (intra enterprise) • Where we are now • Same environment as distributed components • Service Oriented Architecture used to expose components to aid interoperability • Business 2 Business (cross enterprise) • The aim of Service Oriented Computing • Developers no longer have autonomy over the whole system • Presents a series of “Context Horizons”, new challenges Cyprus Workshop 25-26th September 2003

9. Challenges for SOC in cross enterprise • Trust • Expressing/Matching Quality of Service • Security • Reliability/Availability/Performance • Expressing/Matching Service Capability • Semantics • Formal Methods • Expressing/Matching Behavior • Workflows • Enforcement • Contracts • Service Level Agreements • Negotiation • Metering Cyprus Workshop 25-26th September 2003

10. A CBSE Approach • Can the CBSE process be used as a basis for engineering services in a cross enterprise environment. • Development for reuse • Component developers become Service Providers (More Roles) • Providers are responsible for hardware, OS and middleware have to ensure levels of quality of service, including security, reliability, performance • Development with reuse • Application developers become Service consumers • Discovery & Verification of online services is difficult placing a dependency on trust • Developers no longer have autonomy over the middleware/OS/hardware that services Cyprus Workshop 25-26th September 2003

11. Related Paradigms • GRID computing • E-Science field • Open Grid Services Architecture (Globus 3.0 Toolkit) • Is extension to Service Oriented Architecture with lifetime management, state data, and notification capabilities • Semantic Web • Leading towards Agent based Computing • Ontology based languages such as OWL, DAML-S • Peer 2 Peer Networks Cyprus Workshop 25-26th September 2003

12. Summary • Service Oriented Computing primarily driven by web services will promise intra and cross-enterprise systems • There are large gaps in the standards/technology beyond the base of SOA SOAP, WSDL, and UDDI • CBSE may be an appropriate starting point for a service based engineering approach SOC • 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 2003

13. Discussion Cyprus Workshop 25-26th September 2003