xml web services architecture siddharth ruchandani cs 6362 – sw architecture & design summer...
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XML Web Services Architecture
Siddharth RuchandaniCS 6362 – SW Architecture & DesignSummer 200507/11/05
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
<m:GetContactInfo xmlns:m="http://example.org/CompanyInfo"> <ContactName>Sidd R.</ContactName> <CompanyName>SARK</CompanyName> <StreetName>W. Las Colinas</StreetName>
</m:GetContactInfo>
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: <Envelope>, <Header>, <Body>
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)
WSDL (Example)
http://www.xmethods.com/ve2/ViewListing.po;(QHyMHiRM)?key=uuid:D784C184-99B2-DA25-ED45-3665D11A12E5
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
SDMS SPARTA OTHER
SCAUTHENTICATION SERVICE
Web Service to authenticate
applications against Active Directory (AD)
Case Studies
SDMS SPARTA OTHER
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
References
http://msdn.microsoft.com/webservices http://www.gotdotnet.com/team/XMLwebs
ervices/ http://searchwebservices.techtarget.com