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Web Service Standards Relevant to SOA

Web Service Standards Relevant to SOA. By Mark Zalar. Seminar Outline. SOA basics Web Services Web Service Protocol Stack Overview Closer look at each level Protocols and how they’re used Tools Alternative SOA web service tool and protocol. What is SOA?. Service-Oriented Architecture

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Web Service Standards Relevant to SOA

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  1. Web Service Standards Relevant to SOA By Mark Zalar

  2. Seminar Outline • SOA basics • Web Services • Web Service Protocol Stack • Overview • Closer look at each level • Protocols and how they’re used • Tools • Alternative SOA web service tool and protocol

  3. What is SOA? • Service-Oriented Architecture • An architecture that relies on loosely-coupled software agents to perform specified tasks • Software agents can be independent of one another • Interaction requires no knowledge of a software agent’s underlying details

  4. What is SOA? • Loose-coupling • An approach/design goal where interaction between services is developed with minimal assumptions between the services • A change in one service should not force a change in another service that interacts with it • Interface is independent of implementation

  5. What is SOA? • Service • A unit of work performed by a service provider for a service consumer • Service providers and service consumers are both software agents

  6. What is SOA? • Web Services • A software system designed to support interoperable machine to machine interaction over a network (W3C definition) • A web service is SOA if: • Interfaces are based on Internet protocols • Messages are XML

  7. SOA and Web Service Standards • SOA web services are typically built on web service standards (a.k.a. web service specifications) • More interoperability • Freedom from proprietary vendor software • Many of these standards, like SOAP, already have widespread industry acceptance

  8. SOA and Web Service Standards • The base level web service standards relevant to SOA are common standards that most of us have used or at least heard of. • XML, HTTP, SOAP, etc. • These standards can be usefully categorized using the web services protocol stack

  9. Web Services Protocol Stack • The web service protocol stack is a collection of computer networking protocols that are used to: • Define web services • Locate web services • Implement web services • Make web services interact with each other

  10. Web Services Protocol Stack • Four major parts • Service Transport • HTTP, SMTP, FTP • XML Messaging • XML, SOAP • Service Description • WSDL • Service Discovery • UDDI

  11. Web Services Protocol Stack • What is each part responsible for? • Service transport • Transporting messages between network applications • XML messaging • Message encoding in a common XML format so messages can be understood at both ends of a connection • Service description • Standardized Description of how to interface with the web service • Service discovery • Centralized registry where web services can publish their location and description

  12. Web Services: The Big Picture Image from Wikipedia link

  13. Service Transport • HTTP • Hypertext Transfer Protocol • Request/response protocol between clients & servers • HTML • SMTP • Simple Mail Transfer Protocol • e-mail • FTP • File Transfer Protocol • Exchanging files over a network

  14. XML Messaging • XML • Extensible Markup Language • General-purpose • Open, free standard • Used to share data between systems • Human readable • Can represent general data structures • Trees, lists, etc. • Hierarchical structure

  15. XML Messaging • XML Example <?xml version="1.0" encoding="UTF-8"?> <recipe name="bread" prep_time="5 mins" cook_time="3 hours"> <title>Basic bread</title> <ingredient amount="3" unit="cups">Flour</ingredient> <ingredient amount="0.25" unit="ounce">Yeast</ingredient> <ingredient amount="1.5" unit="cups" state="warm">Water</ingredient> <ingredient amount="1" unit="teaspoon">Salt</ingredient> <instructions> <step>Mix all ingredients together, and knead thoroughly.</step> <step>Cover with a cloth, and leave for one hour in warm room.</step> <step>Knead again, place in a tin, and then bake in the oven.</step> </instructions> </recipe> Example from Wikipedia

  16. XML Messaging • Genshi • A Python library for parsing and generating XML Image from Genshi website

  17. XML Messaging • SOAP • Simple Object Access Protocol • Used to exchange XML messages over a network (using HTTP or other service transport protocol) • Most common messaging pattern is RPC • Client sends request, server immediately responds • Allows easy interaction between very different systems

  18. XML Messaging • SOAP Example • Client request <soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"> <soap:Body> <getProductDetails xmlns="http://warehouse.example.com/ws"> <productID>827635</productID> </getProductDetails> </soap:Body> </soap:Envelope> Example from Wikipedia

  19. XML Messaging • SOAP Example • Server response <soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"> <soap:Body> <getProductDetailsResponse xmlns="http://warehouse.example.com/ws"> <getProductDetailsResult> <productName>Toptimate 3-Piece Set</productName> <productID>827635</productID> <description>3-Piece luggage set. Black Polyester.</description> <price currency="NIS">96.50</price> <inStock>true</inStock> </getProductDetailsResult> </getProductDetailsResponse> </soap:Body> </soap:Envelope> Example from Wikipedia

  20. Service Description • WSDL • Web Service Definition Language • An XML format for describing web services • Describes the public interface to a particular web service • Data Types <types> • Messages <message> • Operations <portType> • Communication Protocols <binding> • Often used with SOAP and XML • WSDL tells a client what functions are available • The client uses SOAP to actually call functions

  21. Service Description • WSDL Example <message name="getTermRequest"> <part name="term" type="xs:string"/> </message> <message name="getTermResponse"> <part name="value" type="xs:string"/> </message> <portType name="glossaryTerms"> <operation name="getTerm"> <input message="getTermRequest"/> <output message="getTermResponse"/> </operation> </portType> Example from W3Schools

  22. Service Discovery • UDDI • Universal Description Discovery and Integration • XML-based, platform independent, standardized worldwide business registry • Businesses can publish service listings and describe how services interact over the Internet • Focuses on the discovery aspect of SOA • Three types of information can be registered into a UDDI registry • White Pages - business identification information (address, name, contact information) • Yellow Pages - characterization/description of service • Green Pages - technical information about service • Used with SOAP messages to access WSDL documents describing services in the directory

  23. Service Discovery Table from uddi.org

  24. Service Discovery • UDDI Example • http://soapclient.com/uddisearch.html

  25. Other SOA Web Services Options • Although the standards discussed offer much flexibility for service-oriented development, they are not the only means to implement SOA web services. • Almost any service-based technology will work • Service oriented systems have been implemented using • Jini • CORBA

  26. Jini • Originally developed by Sun, now Apache (Apache River) • Jini is used to create distributed services • Java Based • Seven suite used to develop and deploy services • Both a specification and an implementation • Has discovery features

  27. Jini • Jini service browser example Image from Warren Strange

  28. CORBA • Distributed programming protocol • Jini uses CORBA • Standard defined by Object Management Group • Allows interoperation between software components written in different languages running on different computers • Wraps code with a description that contains information about what the code can do and how to use it • Uses an interface definition language to specify how code interacts • Mappings exist between the interface definition language and implementation programming languages • Ada, C, C++, Lisp, Smalltalk, Java, COBOL, PL/I, and Python

  29. CORBA Image from Wikipedia

  30. Summary • SOA • Web Service Protocol Stack • Service Transport • HTTP, SMTP, FTP • XML Messaging • XML, SOAP • Service Description • WSDL • Service Discovery • UDDI • Alternatives • Jini, CORBA

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