1. SOAP, WSDL & introduction to UDDI
Presentation 7:
SOAP, WSDL & introduction to UDDI

2. Outline Overview of Web Services & SOAP Service-Oriented Architecture
Service Description
Service Registration and Discovery
Service Execution
Emerging Web Services standards:
SOAP, WSDL, UDDI (introduced)

3. Web Service Defined W3C definition:
[Definition: A Web service is a software system designed to support interoperable machine-to-machine interaction over a network. It has an interface described in a machine-processable format (specifically WSDL). Other systems interact with the Web service in a manner prescribed by its description using SOAP messages, typically conveyed using HTTP with an XML serialization in conjunction with other Web-related standards.]

4. Overview SOAP & Web services
SOAP – Simple Object Access Protocol - & Web services:
A light-weight & ultra heterogenic alternative to CORBA, DCOM & RMI
Openness in focus – meant for opening legacy applications for others
Not meant in the role of Inter business, large scale, transaction heavy communication (as CORBA & J2EE)
But can prob. be used for it!
Does not have services for transactions, concurrency, persistence, scalability
Does have discovery services (UDDI) giving some degree of location transparency
Does have Interface Definition Language for heterogeneity (WSDL)
Fails on several of the dist. system requirements!
But easy to implement yourself!

5. Why SOAP When We Have CORBA?
CORBA has been considered too complex by many
May not be true with new development tools using wizards
They aim at solving different tasks:
SOAP covers light-weight application integration within the enterprise, exposing legacy business objects across enterprises, and sharing resources (like Google Search Engine, or Sonofon SMS/MMS API) on the net, as well as technology openness
CORBA has a wide range of services for (as we shall see later):
Locating, creating & moving objects
Object relationship management between hosts
Persistency services – activation frameworks etc.
Distributed concurrency and transaction management
Security
Only some are supported in SOAP tech family – its lightweight
Lesson: define your needs – and find the right technology

6. Regarding SOAP SOAP is not by it self revolutionary – its merely:
a framework for exchanging XML-based information in a network (via protocols of the TCP/IP family) – with RPC capabilities
the currently most hyped XML / Web service technology
But when combined with other technologies like
WSDL &
UDDI
It solves several of the requirements of a Distributed System
And the fact that it is an open standard – supported by all major software vendors and programming languages:
C++
Java C#
Delphi
Visual Basic and many more
Makes it somewhat revolutionary! A practical solution – like WWW

7. Examples of Web Services
Google's Web Service - access the Google search engine
Amazon's Web Service - access Amazon's product information
XMethods - collection of information about existing Web services
SalCentral - WSDL / SOAP Web services search-engine

8. Google Web Service

9. Service-Oriented Architecture (SOA)
Opening up for doing business (the sharing of objects) on the Internet 3
Client
Server
Legacy
code on
server 1 2
Registry
Abstract Architecture
- Web service stack

10. Technologies for Implementing SOA
SOAP for communication
WSDL for contract & binding
UDDI & WSDL for registration & discovery

11. SOAP
SOAP is used for Client/Server communications

12. What is SOAP? Simple Object Access Protocol Wire protocol similar to
IIOP for CORBA
JRMP for RMI
XML is used for data encoding
“text” based protocol vs. “binary” protocol
Supports XML-based RPC

13. What is Not SOAP? Not a component model Not a programming language
So it will not replace objects and components, i.e. EJB, JavaBeans and .NET
Not a programming language
So it will not replace Java, C# og C++
Not a solution for all
So it will not replace other distributed computing technologies such as RMI and CORBA

14. Where is SOAP? W3C XML Protocol working group
SOAP 1.2 current version:
Microsoft, SUN, Oracle, HP, IBM all support the W3C recommendation
but there are still differences to be overcome
security issues, transactions etc.

15. What does SOAP define? Message Envelope Encoding Rules RPC Convention
Binding with underlying protocols
HTTP (which we will use in this course)
SMTP
FTP and others

16. SOAP Message Format
Possible to Attach binaries (images, cryptographic material) to attachments

17. SOAP Message Envelope Encoding information Header Body Optional
Could contain context knowledge
Security
Transaction
Body
RPC methods and parameters
Contains application data

18. Two types of communication

19. SOAP RPC Request Example
<SOAP-ENV:Envelope
xmlns:SOAP-ENV="…"
SOAP-ENV:encodingStyle="…">
<SOAP-ENV:Header>
<!-- Optional context information -->
</SOAP-ENV:Header>
<SOAP-ENV:Body>
<m:GetLastTradePrice xmlns:m=“some_URI">
<tickerSymbol>SUNW</tickerSymbol>
</m:GetLastTradePrice>
</SOAP-ENV:Body>
</SOAP-ENV:Envelope>

20. SOAP RPC Response Example
<SOAP-ENV:Envelope
xmlns:SOAP-ENV="…"
SOAP-ENV:encodingStyle="…">
<SOAP-ENV:Header>
<!-- Optional context information -->
</SOAP-ENV:Header>
<SOAP-ENV:Body>
<m:GetLastTradePriceResponse xmlns:m=“some_URI">
<price>30.5</price>
</m:GetLastTradePriceResponse>
</SOAP-ENV:Body>
</SOAP-ENV:Envelope>

21. SOAP RPC composition I Information needed for a method call:
The URI of the target object (marked with red)
<SOAP-ENV:Body>
<m:GetLastTradePrice xmlns:m=“
<tickerSymbol>SUNW</tickerSymbol>
</m:GetLastTradePrice>
</SOAP-ENV:Body>

22. SOAP RPC composition II
Information needed for a method call:
The URI of the target object
The Method Name
<SOAP-ENV:Body>
<m:GetLastTradePrice xmlns:m=“
<tickerSymbol>SUNW</tickerSymbol>
</m:GetLastTradePrice>
</SOAP-ENV:Body>

23. SOAP RPC composition III
Information needed for a method call:
The URI of the target object
The Method Name
Parameters
Binding protocol (next slide)
<SOAP-ENV:Body>
<m:GetLastTradePrice xmlns:m=“
<tickerSymbol>SUNW</tickerSymbol>
</m:GetLastTradePrice>
</SOAP-ENV:Body>
Name is not important

24. SOAP RPC composition IV: complete SOAP RPC Request
STEP 4: BINDING TO PROTOCOL
POST /StockQuote HTTP/1.1
Host:
Content-Type: text/xml; charset="utf-8"
Content-Length: nnnn
SOAPAction: "Some-URI"
<SOAP-ENV:Envelope
xmlns:SOAP-ENV=”
SOAP-ENV:encodingStyle=”
<SOAP-ENV:Body>
<m:GetLastTradePrice xmlns:m="
<tickerSymbol>SUNW</tickerSymbol>
</m:GetLastTradePrice>
</SOAP-ENV:Body>
</SOAP-ENV:Envelope>
HTTP
Name-space
Encoding

25. Request to HelloWorld.jws
HTTP Host Target
HTTP Post Call
Method name
Input parameters type string

26. … and the HTTP Response from Server
Apache Tomcat Server Responding
HTTP Response
Method Response
Parameter name
Parameter value

27. In addition
There is:
Response handling
Fault handling

28. Lucky us Luckly we dont have to understand SOAP
So it does not really matter that it is somewhat complex
Unless we want to develop clients that do not have a SOAP API
... But then we need an XML parser … and more …
BUT IT IS POSSIBLE and might be feasible

29. Issues with SOAP Issues with SOAP Low performance
Lack of business semantics
Insufficient functionality for business operations
Security
Reliability
Under development
Low performance

30. WSDL
WSDL is used for describing WebServices

31. What is WSDL? XML language for describing web services
Web service is described as
– A set of communication endpoints (ports)
Endpoint is made of
Abstract definitions of operations and messages
Concrete binding to networking protocol and message format

32. Why WSDL?
Enables automation of communication details between communicating partners
Machines can read WSDL
Machines can invoke a service defined in WSDL
Note that WSDL defines only low-level aspects of Web services, however other technologies might follow …
Security
Transactions
Persistency

33. WSDL Document Example Simple service providing stock quotes
A single operation called GetLastTradePrice
Deployed using SOAP 1.1 over HTTP
Request takes a ticker symbol of type string
Response returns price as a float

34. WSDL Elements Types Data type definitions
Used to describe exchanged messages
Uses W3C XML Schema as canonical type system

35. WSDL Example: Types

36. WSDL Elements Messages Operations Port type
Abstract, typed definitions of data being exchanged
Operations
Abstract description of an action
Refers to input and output messages
Port type
Collection of operations
Resembles a Class in OOPL

37. Example: Messages, Operation, Port type

38. WSDL Elements Binding Port Service
Concrete protocol and data format for a particular Port type
Example: SOAP 1.1, HTTP, MIME
Port
Defines a single communication endpoint
Address for binding
URL for HTTP, address for SMTP
Service
Aggregate set of related ports

39. HelloWorld.jws?wsdl

40. Tools Generate WSDL document from Generate SOAP messages from JAX-RPC
existing Java classes or EJB components
AXIS: Java2WSDL
Generate SOAP messages from
WSDL document (via client stub and server skeleton)
JAX-RPC
Part of J2EE from Sun (needs AS)
IDE Tools:
NetBeans, Eclipse, Forte for Java, JBuilder, JDeveloper
Microsoft:
IIS for services and Visual Studio for IDE

41. UDDI
UDDI for publishing & discovery – the SOA

42. UDDI Universel Descrition, Discovery & Integration
UDDI defines a scheme to publish and discover information about Webservices
Programmatic registration and discovery business entities and their Webservices
Based on SOAP, HTTP, XML
Registry data
Business registrations
Service type definitions

43. Registration “ White pages” “ Yellow pages” “ Green pages”
– Address, contact, and known identifiers
“ Yellow pages”
industrial categorizations
Industry: NAICS (Industry codes - US Govt.)
Product/Services: UN/SPSC (ECMA)
Location: Geographical taxonomy
“ Green pages”
technical information about services

44. What uses UDDI? Tool building client (Service Consumer)
Browse or search registry
Create a service proxy
Tool publishing the service
Generates WSDL
Construct UDDI entries
Application that needs dynamic binding
Directly access UDDI
Query can be pre-generated