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Introduction to Web Services. Presented by Sarath Chandra Dorbala. Outline. Definitions Basic Standards SOAP WSDL UDDI. Definitions. - PowerPoint PPT Presentation
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Definitions
A Web Service is a software component that is described via WSDL and is capable of being accessed via standard network protocols such as but not limited to SOAP over HTTP.www.oasis-open.org/committees/wsia/glossary/wsia-draft-glossary-03.htm
The W3C defines a Web service as a software system designed to support interoperable Machine to Machine interaction over a network. http://en.wikipedia.org/wiki/Web_service
An Internet hosted application controlled through SOAP requests which returns results as SOAP responses. http://www.gateway2sms.com/glossary.asp
Basic Standards
XML– All web service documents are written in XML– XML Schemas are used to define elements used in Web
Service communication
SOAP– Communication is done over SOAP (typically)– Request and responses messages are encoded in SOAP– The body of the message is contained with in SOAP
envelope– Binds the client to the web service
WSDL– Describes the web service and defines functions that are exposed
in the web service– Defines SOAP message format
UDDI– UDDI is used to register and look up services with a central
registry– Service Providers can publish information about their business and
the services that they offer– Service consumers can look up services that are available by
Business Service category Specific service
SOAP
Stands for Simple Object Access Protocol It is a platform independent, XML bases
communication protocol for message exchanging between applications
Elements of SOAP message
SOAP is a XML document with the following elements
Envelope– Used to identify the SOAP message
Header (Optional)– This element contains header. For this course this part is
important for incorporating security into web services Body
– This element contains call and response information Fault (Optional)
– This element contains details about processing errors
Skeleton SOAP Message
<?xml version="1.0"?> <soap:Envelope xmlns:soap="http://www.w3.org/2001/12/soap-envelope"
soap:encodingStyle="http://www.w3.org/2001/12/soap-encoding"><soap:Header> ... ...</soap:Header><soap:Body> ... ...<soap:Fault> ... ... </soap:Fault></soap:Body></soap:Envelope>
Sample SOAP Message
SOAP Request
POST /InStock HTTP/1.1Host: www.example.orgContent-Type: application/soap+xml; charset=utf-8Content-Length: nnn
<?xml version="1.0"?><soap:Envelope xmlns:soap="http://www.w3.org/2001/12/soap-envelope"
soap:encodingStyle="http://www.w3.org/2001/12/soap-encoding"><soap:Body xmlns:m="http://www.example.org/stock">
<m:GetStockPrice><m:StockName>IBM</m:StockName>
</m:GetStockPrice></soap:Body></soap:Envelope>
SOAP Response
HTTP/1.1 200 OKContent-Type: application/soap+xml; charset=utf-8Content-Length: nnn
<?xml version="1.0"?><soap:Envelope xmlns:soap="http://www.w3.org/2001/12/soap-envelope"
soap:encodingStyle="http://www.w3.org/2001/12/soap-encoding"><soap:Body xmlns:m="http://www.example.org/stock">
<m:GetStockPriceResponse><m:Price>34.5</m:Price>
</m:GetStockPriceResponse></soap:Body></soap:Envelope>
WSDL
WSDL stands for Web Service Description Language
It is an XML Document that describes a web service
It specifies the location of the service and operations it exposes
Elements of WSDL
<portType>– It describes a web service, the operations that can be
performed, and the messages that are involved. <message>
– Defines the data elements of an operation. Eg, Parameters to the function call parameters
<types>– Defines the data types used by the web service
<binding>– Defines the message format and protocol bindings for each
port
Skeleton WSDL Document
<definitions><types>
definition of types........</types><message>
definition of a message....</message><portType>
definition of a port.......</portType><binding>
definition of a binding.... </binding></definitions>
UDDI
UDDI stands for Universal Description, Discovery and Integration
UDDI is a platform-independent framework for describing services, discovering businesses, and integrating business services by using the Internet.
Advantages of UDDI
Finding the right business from millions Defines how to enable e-commerce once
business is found Describing services and business processes
programmatically in a single, open and secure environment.
Conclusions
We have seen the essential components of a Web Service.
We have seen the brief overview of these components that form the building blocks of a web service
Recommendations
Examine the real WSDL documents and realize its components
Here is a sample WSDL
http://cs.odu.edu/~sdorbala/wsdl/joft.wsdl Tutorials for creating web services both in .NET and
in Java are availablehttp://cs.odu.edu/~sdorbala/ws/JavawebInstr.pdf
http://cs.odu.edu/~sdorbala/ws/instructions_net2003.pdf