XML Web Services Architecture Siddharth Ruchandani CS 6362 – SW Architecture & Design Summer /11/05

Current Business Situation Systems “built to task, built to last” work well independently Accomplish what they were designed for But what if these systems want to connect together?

The Problem Most systems aren’t designed to work with each other Connecting the Accounting with Sales system is expensive, time-consuming, and unreliable

The Solution A standard way for systems to communicate with each other

The Solution A standard way for systems to communicate with each other XML Web Services No need to re- design existing components

The Solution A standard way for systems to communicate with each other XML Web Services No need to re-design existing components Not only connect systems, connect people

Web Services Provide a way for systems to interoperate across different platforms & operating systems Structured way to format data, describe service capability and availability

Web Service Principles Message Orientation – Web services communicate using messages Protocol Composability – Web services avoid monolithic design by the use of modular building blocks that can be re-used Autonomous Services – Can be designed, implemented, managed, versioned, and deployed independently Managed transparency – can manage which functionalities we want to make available to the end-service and which to hide Protocol-based integration – can be implemented using simple protocols

Web Services Architecture HTTP – Hyper Text Transfer Protocol XML – Extensible Markup Language SOAP – Simple Object Access Protocol WSDL – Web Service Description Language UDDI – Universal Description, Discovery & Integration Web Service layers Transport (HTTP) Encoding (XML) Standard structure (SOAP) Description (WSDL) Discovery (UDDI)

XML – eXtensible Markup Language Unit of Information transfer Simple, text-based Message – an XML document information item as defined by the XML Infoset Infoset – Abstract data model, foundation of XML Specifications (XML Schema, XML Query, XSLT)

XML – eXtensible Markup Language Sidd R. SARK W. Las Colinas

XSD XML Schema Definition Schema - an abstract representation of an object's characteristics and relationship to other objects XML schema represents the interrelationship between the attributes and elements of an XML object (for example, a document or a portion of a document) Provides a universal type system, allowing data types to be defined and passed across platforms. For an XML Web service, XSD defines the structure and data types for the XML encapsulated within a SOAP message sent to and from an XML Web service. For example, within a schema for a document describing a Web site, you would define a Web site element, a Web page element, and other elements that describe possible content divisions within any page on that site.

SOAP SOAP(Simple Object Access Protocol) is a lightweight protocol intended for exchanging structured information in a decentralized, distributed environment. SOAP uses XML technologies to define an extensible messaging framework, which provides a message construct that can be exchanged over a variety of underlying protocols. The framework has been designed to be independent of any particular programming model and other implementation specific semantics. SOAP 1.2 Specification definition XML document containing 3 elements:,,

SOAP SOAP Over HTTP

SOAP Processing Model Identify the header block intended for the current SOAP node If header block cannot be processed, message is discarded and fault message generated Process message If current node not the ultimate receiver, then message is relayed to the next SOAP node

WSDL Web Service Definition Language Describes  What a request message must contain  What the response message might look like  Where the service is available  What protocol required to talk to the service

WSDL WSDL documents can maintain information like method signatures, data returned, etc. about a web service Applications can maintain a pointer to the required web service’s WSDL docs Applications can then call the various methods of the web service

WSDL (Example)

UDDI Universal Description Discovery & Integration Analogous to a phonebook Specifies protocol for querying a directory of web services

UDDI A UDDI director entry has 3 primary parts  Service provider – to contact someone responsible for the service  Web services offered – organized by application area, geography, etc.  Bindings to implementation – associates web service entry to the exact URI, protocol to use for access

XML Web Service Lifetime The client creates a new instance of an XML Web service proxy class. This object resides on the same computer as the client. The client invokes a method on the proxy class. The infrastructure on the client computer serializes the arguments of the XML Web service method into a SOAP message and sends it over the network to the XML Web service.

XML Web Service Lifetime (contd.) The infrastructure receives the SOAP message and deserializes the XML. It creates an instance of the class implementing the XML Web service and invokes the XML Web service method, passing in the deserialized XML as arguments. The XML Web service method executes its code, eventually setting the return value and any out parameters. The infrastructure on the Web server serializes the return value and out parameters into a SOAP message and sends it over the network back to the client. The XML Web service infrastructure, on the client computer, receives the SOAP message, deserializes the XML into the return value and any out parameters, and passes them to the instance of the proxy class. The client receives the return value and any out parameters.

Other Features Security - Organizations building and managing secure XML Web services need to ensure that only authorized parties are allowed to use the XML Web services and that the SOAP messages sent and received by the XML Web services can only be modified or viewed by appropriate parties. WS-Security is a simple, stateless, SOAP specification that describes how digital credentials should be placed within SOAP messages, and how these credentials should be associated with a message to ensure message integrity and confidentiality.

Other Features Reliable Messaging WS-ReliableMessaging Specification The specification defines three different assurances that may be used in combination:  At-Least-Once Delivery: Each message is delivered at least one time.  At-Most-Once Delivery: Duplicate messages will not be delivered.  In-Order Delivery: Messages are delivered in the same order they were sent.

Case Studies OSS (Operations Support System) Localization Manager Currency Exchange Web Service GetRate() SendRate()

Case Studies SDMSSPARTAOTHER SCAUTHENTICATION SERVICE Web Service to authenticate applications against Active Directory (AD)

Case Studies SDMSSPARTAOTHER STORE LOCATOR WEB SERVICE Web Service to locate stores by Store number, division, market, or geographical location

Conclusion Web Services  Loosely coupled  Ubiquitous Communication  Universal Data Format Discussed Important components of Web Services Architecture  XML  XSD  SOAP  WSDL  UDDI Secure, Reliable Messaging Application Integration Platform independence Transport independence

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