1. Distributed Computing 9 Sep,2008
Web Services
Distributed Computing
9 Sep,2008
Shahid Mahmood

2. Service
A service is a function that is well-defined, self-contained, and does not depend on the context or state of other services

3. What’s Web Service?
“Software application identified by a URI, whose interfaces and bindings are capable of being defined, described, and discovered as XML artifacts” – W3C Web Services Architecture Requirements, Oct. 2002
“Programmable application logic accessible using Standard Internet Protocols…” – Microsoft
“An interface that describes a collection of operations that are network accessible through standardized XML messaging …” – IBM
“Software components that can be spontaneously discovered, combined, and recombined to provide a solution to the user’s problem/request … “ - SUN

4. Web Services: The Next Horizon for e-business
Allow companies to reduce the cost of doing e-business, to deploy solutions faster
Need a common program-to-program communications model
Allow heterogeneous applications to be integrated more rapidly, easily and less expensively
Facilitate deploying and providing access to business functions over the Web

5. Web Service Interface
A web service interface generally consists of a collection of operations that can be used by the client over the internet.
A web service may either be managed by a web server along with the web pages or it may be totally separate service.
Web Servers such as Google, Amazon, Yahoo, eBay provides web service interfaces to manipulate their resources

6. Web services communication pattern
Web services can process XML- formatted SOAP messages.
An alternative is the REST(representational state transfer) approach.
Web services communication can be
Synchronous/Asynchronous
Event Based

7. Combination of web services
The ‘travel agent service’ combines other web services
hotel booking
Travel Agent
flight booking
hire car booking
Service
Client

8. Underlying Technologies XML Is the Glue
Program the Web
XML
Browse the Web
HTML
TCP/IP
Connect the Web
Technology
Innovation
Connectivity
Presentation
Connecting
Applications
FTP, , Gopher
Web Pages
Web Services

9. What is XML? XML is a “use everywhere” data specification
Application X
XML
Documents
Configuration
XML
XML
Repository
Database

10. Web services infrastructure and components
Security
Service descriptions (in WSDL)
Applications
Directory service
Web Services
XML
Choreography
SOAP
URIs (URLs or URNs)
HTTP, SMTP or other transport

11. Web Service Stack

12. SOAP: Simple Object Access Protocol
What is SOAP?
SOAP is a communication protocol
SOAP is for communication between applications
SOAP is a format for sending messages
SOAP is designed to communicate via Internet
SOAP is platform independent
SOAP is language independent
SOAP is based on XML
SOAP is simple and extensible
SOAP will be developed as a W3C standard

13. SOAP: Simple Object Access Protocol
SOAP 1.0: Microsoft, Userland, DevelopMentor
Specific to COM and HTTP
SOAP 1.1: includes contributions from IBM and Lotus
Substitutable transport binding (not just HTTP)
Substitutable language binding (e.g. Java)
Substitutable data encoding
Completely vendor-neutral
Independent of: programming language, object model, operating system, or platform
SOAP 1.2: current working draft from w3.org “XML Protocol” working group

14. SOAP Message Structure
Request and Response messages
Request invokes a method on a
remote object
Response returns result of running
the method
SOAP specification defines an “envelop”
“envelop” wraps the message itself
Message is a different vocabulary
Namespace prefix is used to distinguish the two parts
Application-specific message vocabulary
SOAP Envelop vocabulary

15. SOAP message in an envelope
header
body
header element
body element

16. SOAP Example of a simple request without headers
m:exchange
env:envelope
xmlns:env =namespace URI for SOAP envelopes
m:arg1
env:body
xmlns:m = namespace URI of the service description
Hello
m:arg2
World
In this figure and the next, each XML element is represented by a shaded box with its name in italic followed by any attributes and its content

17. Example of a reply to the request
env:envelope
xmlns:env = namespace URI for SOAP envelope
m:res1
env:body
xmlns:m = namespace URI for the service description
m:res2
World
m:exchangeResponse
Hello

18. HTTP POST Request in SOAP client-server communication
endpoint address
action
POST /examples/stringer
Host:
Content-Type: application/soap+xml
Action:
<env:envelope xmlns:env=
namespace URI for SOAP envelope
>
<env:header> </env:header>
<env:body> </env:body>
</env:Envelope>
message
Soap
header
HTTP

19. SOAP Request Message <?xml version="1.0"?> <soap:Envelope
Namespace
<?xml version="1.0"?>
<soap:Envelope
xmlns:soap="
soap:encodingStyle="
<soap:Body xmlns:m="
</soap:Body>
</soap:Envelope>
<m:GetStockPrice>
<m:StockName>IBM</m:StockName>
</m:GetStockPrice>
Message
SOAP Envelope
Message
Namespace

20. SOAP Response Message <?xml version="1.0"?> <soap:Envelope
xmlns:soap="
soap:encodingStyle="
<soap:Body xmlns:m="
</soap:Body>
</soap:Envelope>
<m:GetStockPriceResponse>
<m:Price>34.5</m:Price>
</m:GetStockPriceResponse>
Message
Result
returned in
Body
SOAP Envelope

21. Why SOAP? Other distributed technologies failed on the Internet
Unix RPC – requires binary-compatible Unix implementations at each endpoint
CORBA – requires compatible ORBs
RMI – requires Java at each endpoint
DCOM – requires Windows at each endpoint
SOAP is the platform-neutral choice
Simply an XML wire format
Places no restrictions on the endpoint implementation technology choices

22. SOAP Usage Models RPC-like message exchange
Request message bundles up method name and parameters
Response message contains method return values
However, it isn’t required by SOAP
SOAP specification allows any kind of body content
Can be XML documents of any type
Example:
Send a purchase order document to the inbox of B2B partner
Expect to receive shipping and exceptions report as response

23. Web Services Description Language
What is WSDL?
WSDL is an XML document
WSDL is used to describe Web services
WSDL is also used to locate Web services
WSDL is a W3C standard
Operational information about the service
Location of the service
Service interface
Implementation details for the service interface

24. Web Services Description Language (WSDL)
is a format for describing a Web Services interface. It is a way to describe services and how they should be bound to specific network addresses. WSDL has three parts:
Definitions
Operations
Service bindings

25. WSDL 2.0 Interface definition for Stock Quote Service
<?xml version="1.0"?> <definitions name="StockQuote“ targetNamespace=" xmlns:tns=" xmlns:xsd1=" xmlns:soap=" xmlns=" <import namespace=" location=" <types> <schema targetNamespace=" <element name="GetLastTradePriceInput" type="xsd1:TradePriceRequest"/> <element name="GetLastTradePriceOutput" type="xsd1:TradePrice"/> </schema> </types> <interface name="StockQuoteInterface"> <operation name="GetLastTradePrice" pattern=" <input message="tns:GetLastTradePriceInput"/> <output message="tns:GetLastTradePriceOutput"/> </operation> </interface> </definitions>

26. WSDL 2.0 Implementation definition for Stock Quote Service
<definitions name="StockQuote“ targetNamespace=" xmlns:tns=" xmlns:wsoap=" xmlns:defs=" xmlns=" <import namespace=" location=" <binding name="StockQuoteSoapBinding" interface="defs:StockQuoteInterface"> <wsoap:binding protocol=" <operation name="GetLastTradePrice"> <wsoap:operation soapAction=" <input> <wsoap:body/> </input> <output> <wsoap:body/> </output> </operation> </binding> <service name="StockQuoteService"> <documentation>My stock quote service</documentation> <endpoint name="StockQuoteEndPoint" binding="tns:StockQuoteSoapBinding"> <wsoap:address location=" </endpoint> </service> </definitions>

27. WSDL – DEFINITION
Are generally expressed in XML, include both data type definitions and message definitions that use the data type definitions.
These definitions are usually based upon some agreed upon XML vocabulary agreement.
within an organization or between organizations.
industry-wide vocabulary.
If data type and message definitions need to be used between organizations, then most likely an industry-wide vocabulary will be used
BussinessXML, AccoutingXML, PhysicsXML, LegalXML, MathXML

28. WSDL - OPERATION
Operations describe actions for the messages supported by a Web service.
There are four types of operations:
One-way: Messages sent without a reply required
Request/response: The sender sends a message and the received a reply.
Solicit response: A request for a response. (The specific definition for this action is pending.)
Notification: Messages sent to multiple receivers. (The specific definition for this action is pending.)

29. WSDL – SERIVCE BINDING Service bindings connect port types to a port.
A port is defined by associating a network address with a port type.
A collection of ports defines a service.
This binding is commonly created using SOAP, but other forms may be used.
These other forms could include
CORBA Internet Inter-ORB Protocol (IIOP),
DCOM, .NET,
Java Message Service (JMS), o
WebSphere MQ to name a few.

30. Basic Parts of WSDL

31. WSDL 2.0 Conceptual Model

32. WSDL 2.0 Skeleton
<definitions targetNamespace="xs:anyURI"> <documentation /> ? [<import /> | <include /> ] * <types /> ? [<interface /> | <binding /> | <service /> ] * </definitions>

33. WSDL 2.0 Skeleton - Definitions
root element of any WSDL document.
serves as a container which holds all the necessary information about the service and its attributes.
targetNamespace attribute of the definitions element is a required attribute of type anyURI.
The namespace can directly or indirectly define the semantics of the WSDL.
Also, the definitions element can have other optional attributes which correspond to various namespaces that may be used with in the WSDL document.

34. WSDL 2.0 Skeleton – Include & Import
element helps to modularize the web service descriptions.
The location attribute is mandatory and specifies the location of these WSDL documents.
The actual value of the target namespace of the included WSDL must match the target namespace of the definitions element in the including WSDL
Import
The concept behind the import element is very similar to that of include element, except that the imported WSDL can be in different target namespaces.
The namespace attribute for the import element is mandatory while the location attribute is optional.

35. WSDL 2.0 Skeleton – Types Types
element defines the data types used by the exchanged messages.
WSDL uses W3C XML Schema as its preferred schema language.
Schemas may be used by importing or embedding within the types element of the WSDL document.
Importing can be done using the construct xs:import while embedding uses the construct xs:schema.

36. WSDL 2.0 Skeleton – Interface
element encloses a named set of abstract operations and the abstract messages.
can optionally extend one or more other interfaces.
interface operation element has name and pattern as required attributes, while style is an optional attribute.
Features defines functionalities associated with the message exchanges between communicating parties, which might include reliability, security, correlation, and routing.
Property is used to control the behavior of a feature. It has a set of possible and permissible values specified by references to a schema description.

37. WSDL 2.0 Skeleton – Binding
element defines the underlying transport and wire format for messages. Each binding in the WSDL references to an interface.
All operations defined within the interface must be bound in the binding.
An endpoint in the service component references a binding.
Both endpoints and bindings are modeled to support flexibility and location transparency.
Multiple endpoints with different network address can still share the same protocol binding.
WSDL 2.0 Bindings specification defines binding extensions for protocols and message formats such as SOAP, HTTP and MIME.

38. WSDL 2.0 Skeleton – Service
element describes a set of endpoints which refer to a single network address for a binding.
All other protocol specific information is contained in the binding. Service can be referred by QName.
service element has a name and interface which are required attributes.

39. Universal Description, Discovery and Integration (UDDI)
What is UDDI?
Directory service where businesses can register and search for Web services
Directory for storing information about web services
Directory of web service interfaces described by WSDL
UDDI communicates via SOAP
What is UDDI Based On?
Uses W3C Internet standards such as XML, HTTP, and DNS protocols
UDDI uses WSDL to describe interfaces to web services

40. WSDL 2.0 Infoset, Schema and Component Model

41. UDDI Roles and Operations
Service Registry
Provides support for publishing and locating services
Like telephone yellow pages
Service Provider
Provides e-business services
Publishes these services through a registry
Service requestor
Finds required services via the Service Broker
Binds to services via Service Provider

42. UDDI Registries and Protocol
UDDI The Vision
Advanced Discovery via Portals and Marketplaces
Marketplace
UDDI Registries and Protocol
Marketplace
Marketplace
The Universal Description, Discovery and Integration (UDDI) specifications define a means for publishing and discovering Web Services. In the light of DISCO it may seem redundant, but UDDI provides more features than DISCO, and arguably in a more efficient manner.
UDDI is based upon a directory service or Business Registry. Businesses can register themselves, their type of business, and technical descriptions of any Web Services they publish in the registry. Other business can query the registry, searching for partners using compatible software or offering Web Services that they could interact with. The aim is to promote faster B2B integration. There are several UDDI registries available, including one at and a test registry at
Naturally, all interactions with a UDDI registry are performed using a defined XML schema, and SOAP.
Search Portal
Search Portal
Business Users
Technical Users

43. How can UDDI be Used?

44. UDDI Benefits
Making it possible to discover the right business from the millions currently online
Defining how to enable commerce once the preferred business is discovered
Reaching new customers and increasing access to current customers
Expanding offerings and extending market reach

45. Thank U

46. Lecture has prepared from Sir Atif Kamal slides with some modifications and enhancement