Description of soa and SOAP,WSDL & UDDI
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This document defines key concepts in service-oriented architectures (SOA) including services, components, standards like SOAP, WSDL, and UDDI. It describes how SOA uses loosely coupled services that communicate through standardized web protocols. Services are defined through WSDL interfaces and discovered through UDDI directories. SOAP is the messaging standard used to enable communication between services. Orchestration and choreography standards like WS-BPEL and WS-CDL are used to compose services to create new composite applications and define allowable message exchanges.
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Description of soa and SOAP,WSDL & UDDI
- 1. 1 Tushar Varshney Description of SOA and SOAP,WSDL&UDDI
- 2. 2 Service-oriented architectures A means of developing distributed systems where the components are stand-alone services. Services may execute on different computers from different service providers. Standard protocols have been developed to support service communication and information exchange.
- 3. 3 Services or components? A service can be defined as: A loosely-coupled, reusable software component that encapsulates discrete functionality which may be distributed and programmatically accessed. A web service is a service that is accessed using standard Internet and XML-based protocols. A critical distinction between a service and a component as defined in component-based software engineering is that services are independent. Services do not have a ‘requires’ interface. Services rely on message-based communication with messages expressed in XML.
- 4. 4 Benefits of SOA Services can be provided locally or outsourced to external providers. Services are language-independent. Investment in legacy systems can be preserved. Inter-organizational computing is facilitated through simplified information exchange.
- 5. 5 SOA and Web Services Service-oriented architecture is an architectural style Derived from the client-server architectural style. Clients (service consumers or requesters) and servers (service providers) connected by a service “bus”. Services defined using formal interfaces (contracts). Service bus supports point-to-point and messaging styles of communication. Support for system qualities, e.g., security and transaction management. Web services Services provided in a SOA deployed over the web.
- 6. 6 Key standards SOAP (Simple Object Access Protocol) A message exchange standard that supports service communication. WSDL (Web Service Definition Language) This standard allows a service interface and its bindings to be defined. UDDI (Universal Description Discovery and Integration) Defines the components of a service specification that may be used to discover the existence of a service.
- 8. 8 SOAP messages SOAP is based on message exchanges Messages are seen as envelops where the application encloses the data to be sent A message has two main parts: header: which can be divided into blocks body: which can be divided into blocks SOAP does not say what to do with the header and the body, it only states that the header is optional and the body is mandatory Use of header and body, however, is implicit. The body is for application level data. The header is for infrastructure level data SOAP Envelope SOAP header Header Block SOAP Body Body Block
- 9. 9 SOAP EnvelopeSOAP Envelope SOAP header Transactional context SOAP Body Input parameter 1 Input parameter 2 Name of Procedure HTTP POST SOAP EnvelopeSOAP Envelope SOAP header Transactional context SOAP Body Return parameter HTTP Acknowledgement SERVICE REQUESTER SERVICE PROVIDER RPC call HTTPengine SOAP engine Procedure HTTPengine SOAP engine SOAP and HTTP
- 10. 10 Web service description language The service interface is defined in a service description expressed in WSDL. The WSDL specification defines: What operations the service supports and the format of the messages that are sent and received by the service. How the service is accessed - that is, the binding maps the abstract interface onto a concrete set of protocols. Where the service is located. This is usually expressed as a URI (Universal Resource Identifier).
- 11. 11 Structure of a WSDL specification Intro Abstract interface Concrete implementation WSDL service definition XML namespace declarations Type declarations Interface declarations Message declarations Binding declarations Endpoint declarations
- 12. 12 A UDDI description Details of the business providing the service. An informal description of the functionality provided by the service. Information where to find the service’s WSDL specification. Subscription information that allows users to register for service updates.
- 13. 13 Standards for web service composition Service orchestration WS-BPEL is an XML-based language for workflow specification. WS-BPEL is an “orchestration” language. Service orchestration defines the sequence and conditions in which one Web service invokes other Web services. Can be used to create a composite service out of other services. Service choreography WS-CDL is an XML-based language for describing service “choreography”. Choreography defines the allowable message exchanges between services.
- 14. 14 Orchestration vs. choreography Orchestration A Single Director In Control. Choreography Defines Interaction.
- 15. 15 Orchestration and choreography example Request processor Setup job parameters Download data Start computation Store results Report completion Restart Fail Check Availability Allocate resources Initialise Compute Return results OK No processor OK Orchestration within services Choreography between services
Editor's Notes
- #6: Open source software for SOA, IONA Technologies A-Trenaman-SOA.pdf