Web services use SOAP, WSDL, and UDDI to enable communication between systems. SOAP defines an XML format for messages, WSDL describes available services and operations, and UDDI provides a directory for services to publish themselves. Services communicate by exchanging SOAP messages, with requests and responses defining common operations, and faults handling errors.

1. Web Services
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2. • SOAP (Simple Object Access Protocol) is a simple
protocol for exchange of information.
• UDDI (Universal Description, Discovery, and
Integration) is a specification designed to allow
businesses of all sizes to benefit in the new digital
economy.
• WSDL (Web Services Description Language) defines
the XML grammar for describing services as
collections of communication endpoints capable of
exchanging messages.
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3. Communication between Web-Service and
heterogeneous clients
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4. Introduction
• A Web service is a method of communication between
two electronic devices over the web (internet).
• It has an interface described in a machine-processable
format (WSDL)
• Other systems interact with the Web service using SOAP
messages
Features of Web Services
• Language Independent
• Operating System Independent
4

5. WSDL
• WSDL is written in XML
• used to describe & locate Web services
WSDL Ports
• The <portType> element is the most
important WSDL element.
• It defines a web service, the operations that
can be performed, and the messages that are
involved.
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6. PortType
<portType name="glossaryTerms">
<operation name="setTerm">
<input name="newTerm"
message="newTermValues"/>
</operation>
</portType >
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7. Operation Types
The request-response type is the most common operation type, but
WSDL defines four types:
Type Definition
One-way The operation can receive a message but
will not return a response
Request-response The operation can receive a request and will
return a response
Solicit-response The operation can send a request and will
wait for a response
Notification The operation can send a message but will
not wait for a response
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8. UDDI
• Universal Description, Discovery and Integration
(UDDI)
• UDDI is a directory for storing information about web
services
• UDDI is a directory of web service interfaces
described by WSDL
• UDDI communicates via SOAP
• UDDI uses WSDL to describe interfaces to web
services
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9. SOAP-based communication
Waiting for
Waiting for Sending
Sending
requests
requests Data in XML format requests,
requests,
(known location,
(known location,
known port)
getting
getting
known port)
results
results
• SOAP:
– Data in a well-defined XML format
– Transport over various protocols
• HTTP, SMTP are the most used, perhaps because
they are firewall-friendly
– server side: either an RPC call or a message delivered

10. SOAP Elements
• Envelope (mandatory)
– Top element of the XML document representing the
message.
• Header (optional)
– Determines how a recipient of a SOAP message should
process the message
– Adds features to the SOAP message such as
authentication, transaction management, payment,
message routes, etc…
• Body (mandatory)
– Exchanges information intended for the recipient of the
message.
– Typical use is for RPC calls and error reporting.

11. SOAP Request
<SOAP-ENV:Envelope
xmlns:SOAP-ENV=“http://schemas.xmlsoap.org/soap/envelope/”
SOAP-ENV:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/”>
<SOAP-ENV:Header>
<t:transId xmlns:t=“http://a.com/trans”>345</t:transId>
</SOAP-ENV:Header>
<SOAP-ENV:Body>
<m:Add xmlns:m=“http://a.com/Calculator”>
<n1>3</n1>
<n2>4</n2>
</m:Add>
</SOAP-ENV:Body>
</SOAP-ENV:Envelope>

12. SOAP Response
<SOAP-ENV:Envelope
xmlns:SOAP-ENV=“http://schemas.xmlsoap.org/soap/envelope/”
SOAP-ENV:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/”>
<SOAP-ENV:Header>
<t:transId xmlns:t=“http://a.com/trans”>345</t:transId>
</SOAP-ENV:Header>
<SOAP-ENV:Body>
<m:AddResponse xmlns:m=“http://a.com/Calculator”>
<result>7</result>
</m:AddResponse>
</SOAP-ENV:Body>
</SOAP-ENV:Envelope>

13. SOAP Fault
• Used to carry error and/or status information within
a SOAP message
• Appears within the SOAP body
• Defines the following:
– faultcode (mandatory)
• algorithmic mechanism for identifying the fault
• defined in the SOAP spec
– Faultstring (mandatory)
• human readable explanation of the fault

14. SOAP Fault
– faultactor (optional)
• information about who caused the fault to happen
• URI value identifying the source
– Detail
• error information related only to the Body element.
• if not present then indicates that the fault is not
related to the Body element.

15. SOAP Fault Example
<SOAP-ENV:Envelope
xmlns:SOAP-ENV=“http://schemas.xmlsoap.org/soap/envelope/”
SOAP-ENV:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/”>
<SOAP-ENV:Body>
<SOAP-ENV:Fault>
<faultcode>SOAP-ENV:Server</faultcode>
<faultstring>Internal Application Error</faultstring>
<detail xmlns:f=“http://www.a.com/CalculatorFault”>
<f:errorCode>794634</f:errorCode>
<f:errorMsg>Divide by zero</f:errorMsg>
</detail>
</SOAP-ENV:Fault>
</SOAP-ENV:Body>
</SOAP-ENV:Envelope>

16. XML Messaging Using SOAP