1. T Network Application Frameworks and XML Web Services and WSDL Sasu Tarkoma Based on slides by Pekka Nikander

2. What is WSDL? WSDL: Web Service Description Language
An XML language used to describe and locate web services
location of web service
methods that are available
data type information and XML messages
Commonly used to describe SOAP-based services
W3C standard (work in progress)
Initial input: WSDL 1.1 as W3C Note
Current version 2.0 (Candidate Recommendation)
Some differences between 1.1 and 2.0
WSDL 1.1 in WS-I Basic Profile 1.0 and 1.1.

3. WSDL Document Elements (v.1.1.)
<types> - data type definitions
<message> - Abstract definition of the data being transmitted
<portType> - A set of abstract operations
<binding> - Concrete protocol and data format specifications for the operations and messages defined by a particular portType. Endpoint type.
<port> - An address for binding. Endpoint instance.
<service> - A set of ports.

4. WSDL Overview <definitions>: ROOT WSDL element
<types>: The data types that are used
<message>: What messages are transmitted?
<portType>: The supported operations
<binding>: The binding to concrete protocols
<service>: Reference to actual location

5. A WSDL Document A WSDL document contains two parts Abstract part
Interfaces, types, messages
Concrete part
Binding to conrete protocol and encoding
May be published separately
Interfaces agreed between many companies
Each company published their own implementation in UDDI and import the abstract interface.

6. Mapping SOAP to WSDL

7. Message Styles
The WSDL 1.1 specification defines two SOAP message styles
Determined in binding
Document
<soap:Body> contains one or more child elements called parts
There are no SOAP formatting rules for what the <soap:Body> contains
preferred, loose coupling, easy validation
RPC
<soap:Body> contains an element with the name of the method or remote procedure being invoked
This element in turn contains an element for each parameter of the procedure
less popular today, tighter coupling

8. The main structure (v.1.1) <definitions namespace = "http://..">
<types>XML Schema types</types>
<message>..</message>
<portType>a set of operations</portType>
<binding>Communication protocols</binding>
<service>A list of binding and ports</service>
</definitions>

9. Types <types> define data types used in message declaration
For platform neutrality, WSDL uses XML Schema syntax to define data
XML Schema must be supported by any vendor of WSDL conformant products
Other kinds of type definitions also possible
Possible interoperability issues
If the service uses only XML Schema built-in simple types, such as strings and integers, the types element is not required

10. WSDL Messages
The <message> element defines the data elements of an operation
the name of the message
contains zero or more message part elements
The parts can be compared to the parameters of a function call in a traditional programming language
All parts are typed by an XML Schema type
V.2.0 changes: message element is not used, replaced by patterns

11. WSDL Ports
The <portType> element is the most important WSDL element
The operations that can be performed, the messages that are involved
A <port> defines the connection point to a web service, an instance of <portType>
It can be compared to a function library (or a module, or a class) in a programming language

12. Operation Types (v.1.1)
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 endpoint sends an output message and then receives an input message.
Notification: The operation can send a message but will not wait for a response
v.2.0 changes: abstract message patterns

13. <message name="GetLastTradePriceInput">
<part name="body" element="TradePriceRequest"/>
</message>
<message name="GetLastTradePriceOutput">
<part name="body" element="TradePrice"/>
<message name=”ExampleInteraction">
<part name="index" type="xsd:integer"/>
<part name="name" type="xsd:string" />

14. Example <portType name="StockQuotePortType">
<operation name="GetLastTradePrice">
<input message="tns:GetLastTradePriceInput"/>
<output message="tns:GetLastTradePriceOutput"/>
</operation>
</portType>

15. One way and Notification Example
<portType name="RegisterPort">
<operation name="register">
<input name="customerInfo" message="RegInfo"/>
</operation>
<operation name="registerResponse">
<output name="response" message="ResponseInfo"/>
</portType>

16. Putting it together
Source:

17. WSDL 2.0 3 specifications Part 1: Core
Abstract interfaces, independent of protocol and encoding
Part 2: Message Exchange Patterns
Predefined types of interactions
Part 3: Bindings
SOAP and HTTP/MIME binding
Lot’s of changes from 1.1

18. Changes from 1.1 to 2.0
Adding further semantics to the description language.
Removal of message constructs. These are specified using the XML schema type system in the types element.
No support for operator overloading.
PortTypes renamed to interfaces. Support for interface inheritance is achieved by using the extends attribute in the interface element.
Ports renamed to endpoints.
Abstracted message patterns

19. WSDL 2.0 Conceptual Model
Source:

20. Message Exchange Patterns
MEP
Description
Fault
in-only
Single input message No
robust-in-only
Single input message
Trigger
In-out
Input message + output message
Replace
out-only
Single output message No
robust-only-out
Single output message
Trigger
out-in
Output followed by input msg
Replace
out-optional-in
Output followed by an opt. Input
Trigger
in-optional-out
Input followed by an opt. Output
Trigger

21. Implementations Microsoft .NET Java API for XML-based RPC (JAX-RPC)
SOAP 1.1, WSDL 1.1
Java API for XML-based RPC (JAX-RPC)
Java API for XML Registries (JAXR)
Apache Axis
Tools for automatically creating WSDL to/from Java
SOAP 1.1 and 1.2, WSDL 1.1, JAX-RPC 1.0
Axis2 supports WSDL 2.0 component model
IBM Websphere, BEA Web Logic, SAP NetWeaver, …

22. Uses of WSDL documents Description of service interfaces
Compile-time
Developer uses WSDL before service deployment
Run-time
Client downloads WSDL description and uses the info it provides to execute the service
As a side-effect
Developers can use WSDL to speed up the development of code
WSDLJava code
Java interfaces  WSDL

23. Summary Deferred binding, using Web, composition
Some details and conventions still unclear
Possible interoperability issues
Parts hard to understand
Namespaces
Schemas
Differences between versions
Document vs. RPC SOAP style
Also literal vs. encoded
More about this next week