Web Services Description Language (WSDL) Jason Glenn CDA 5937 Process Coordination in Service and Computational Grids September 30, 2002.
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Web Services Description Language (WSDL)
Jason GlennCDA 5937
Process Coordination in Service and Computational
GridsSeptember 30, 2002
Outline What is a web service? Web Services Model Web Services Stack Lower level WS protocols What is WSDL? Explain contents of WSDL documents Higher level WS and WS-related
applications
What is a Web Service? Self-contained, modular web
application that can be published, located, and invoked across the Web.
Can perform functions of varying complexities
Once deployed, other applications (and other Web services) can discover and invoke the deployed service.
Web Services Model
Server(Web Service)
Client
WS Request
WS Response
Port
Backend App
Web Services StackImplementation Layer
UDDI Publishing and Discovery
WSXL/.NET Web Applications
IBM WSFL/MS XLANG Workflow
WSDL/WSCL Service Descriptions
SOAP/ XML/ HTTP/SMTP Transactions/Reliability/ Messaging
Internet/ Intranet Transport Network
Common Transfer Protocols HTTP SMTP
HTTP HTTP=HyperText Transfer
Protocol Protocol commonly used to
transfer information on the web
SMTP SMTP = Simple Mail Transfer
Protocol Protocol used to exchange
information between mail servers
MIME MIME = Multipurpose Internet Mail
Extensions Internet standard that specifies
how messages are formatted for exchange between different email systems
flexible format
Review of XML XML = EXtensible Markup Language A markup language like HTML
(HyperText Markup Language) Designed to describe data Tags are not predefined Uses a Document Type Definition
(DTD) or an XML Schema to describe the data
Designed to be self-descriptive
XML vs. HTML XML is about describing
information HTML is about displaying
information
XML Example
<note>
<to>Gerald</to>
<from>Ron</from>
<heading>Reminder</heading>
<body>Don't forget the meeting on Friday.</body>
</note>
HTML Example
<b>This is a note</b><br>
<font face=“arial” size=-1>To: Gerald</font><br>
< font face=“Terminal”>From: Ron</font><br>
<b>Heading: Reminder</b><br><br>
<center>Don't forget the meeting on Friday.</center>
XML Documents Not quite the same as HTML
documents Can be seen independently of files
(one document can contain many files; one file can contain many documents)
Concerned more with logical structure than physical structure
XML Namespaces An XML namespace is a collection
of names, which are used in XML documents as element types and attribute names
WSDL document elements belong to WSDL namespace
SOAP (Simple Object Access Protocol ) a lightweight and simple XML-based
protocol that is designed to exchange structured and typed information on the Web
Standard way of representing remote procedure calls and responses
Standard to encapsulate messages between Web service clients and servers
SOAP Envelope
SOAP
SOAP Envelopes
Server(Web Service)
Client
WS Response
Port
Backend App
WS Request
Soap Envelope/HTTP
Soap Envelope/HTTP
What is WSDL? Web Services Description
Language An XML format for describing
network services as a set of endpoints operating on messages.
Characteristics of WSDL Operations and messages are
described abstractly Endpoints defined by binding
concrete network protocol and message format to abstract operations and messages
Can describe any endpoint regardless of the underlying network protocol or message format
WSDL Document Elements Types – a container for data type definitions using
some type system Message – an abstract, typed definition of the data
being communicated Operation – an abstract description of an action
supported by the service Port Type – an abstract set of operations supported
by one or more endpoints Binding – a concrete protocol and data format
specification for a particular port type Port – a single endpoint defined as a combination of a
binding and a network address Service – a collection of related endpoints
Example
The following example is taken from the WSDL description document provided by the world wide web consortium. This document can be found at http://www.w3.org/TR/wsdl#_wsdl. It is the WSDL definition for a simple service providing stock quotes.
Example
Microsoft Word
Document
Expanding on WSDL WSXL
IBM web services component model based on open standards
.NET Microsoft web services component
model UDDI
Web Service Registry
WSXL Goals
enable businesses to deliver interactive Web applications through multiple distribution channels
enable new services or applications to be created by leveraging other interactive applications across the Web
.NET Goal
Applications constructed from multiple Web services that work together to provide data and services for the application
UDDI Universal Description, Discovery and
Integration Platform-independent, open framework
for describing and discovering web services using the Internet
UDDI Registries
Popular Web Services Servers IBM Websphere
Not Open Source Trial Versions Available
Apache Axis Open Source Free
Useful Links WSDL description/specification
http://www.w3c.org/TR/wsdl Apache Axis
http://xml.apache.org/axis/ IBM Websphere
www.ibm.com/software/info1/websphere
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