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Web Services

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Distributed Systems Maturity in the enterprise, only ... FTP, E-mail, Gopher. Web Pages. Browse. the Web. Program. the Web. Web Services. Some Terminology ... – PowerPoint PPT presentation

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Title: Web Services


1
Web Services
  • Presented By Noam Ben Haim

2
Agenda
  • Introduction
  • What is a web service
  • Basic Architecture
  • Extended Architecture
  • WS Stacks

3
Introduction
  • The Need The expanding WWW is not able to
    communicate correctly.
  • Distributed Systems Maturity in the enterprise,
    only born in WWW.
  • Failure of COM and CORBA to interoperate, lots of
    security issues over the web.

4
Introduction
  • The opportunity evolve of several Web
    Technologies such as SOAP, XML and WSDL.

5
What is a Web Service
  • Software system
  • Identified by URI
  • Defined and described using XML
  • Can be discovered
  • XML based messages over internet protocols

6
  • Web Services are an Architectural Evolution.

EJB
Corba
DCOM
RMI
Main Frame
7
Technology Evolution
8
Some Terminology
  • SOAP Simple Object Access Protocol (remote
    invocation)
  • WSDL Web Service Definition Language (service
    characteristics)
  • UDDI Universal Description, Discovery, and
    Integration (directory)
  • XKMS XML Key Management Specification (under
    development)
  • XML Extensible Markup Language
  • XLANG Transactional support (under development)
  • ebXML (e-business XML)

9
Basic Architecture
  • Various components that comprise a WS Stack
  • Exchanging messages
  • Describing Web services
  • Publishing and Discovering WS description
  • The Basic architecture defines an interactions
    between SW agents

10
Basic Architecture (cont.)
  • Models interactions between three roles
  • Service provider
  • Service discovery agency
  • Service requestor
  • Models three operations
  • Publish
  • Find
  • Bind

11
Basic Architecture (cont.)
Discovery Agency
Service Description
Service Requestor
Service Provider
Service
Client
Service Description
12
Basic Architecture (Cont.)
  • Typical scenario
  • Service provider hosts a network accessible
    software module (an implementation of WS)
  • The service provider defines a service
    description and publishes it.
  • The service requestor uses a find operation to
    retrieve the description from the Disco Agency
  • The Service requestor uses the description to
    bind with the service provider.

13
Basic Architecture (Cont.)
  • Requestors and Providers interact using Message
    Exchange Patterns (MEPs)
  • The description includes data types, MEP info and
    address of the service provider.

14
Basic Architecture (cont.)
  • The Components
  • The Service
  • the implementation of the WS whose description is
    the interface.
  • A software module deployed on the network.
  • It exists to be invoked or to interact with
    service requestor
  • It may also act a a requestor using other WS in
    its implementation

15
Basic Architecture (Cont.)
  • The Components
  • The Service Description
  • Contains the details of the interface and
    implementation
  • Data types, Operations, Binding info, network
    locations.
  • Metadata Categorization, etc.
  • Published to a requestor directly or to a Disco
    Agency

16
Basic Architecture (Cont.)
  • The Roles
  • Service Provider
  • The platform that hosts access to the service.
  • Acts as a server for the requestor in the MEP
  • Service Requestor
  • The application that interacts with the service.
  • Can be played by a browser operated by human or
    by a program with no UI. Acts as a client.

17
Basic Architecture (Cont.)
  • The Roles
  • The Discovery Agency
  • A searchable set of service descriptions.
  • Centralized or Distributed.
  • Can be push or pull.
  • Support static and dynamic binding for apps.

18
Basic Architecture (Cont.)
  • The Operations
  • Publish
  • The service publishes its description such that
    the requestor can find it.
  • Find
  • The service requestor retrieves a service
    description directly or queries the registry.
  • Can be involved in the design time or run time.

19
Basic Architecture (Cont.)
  • The Operations
  • Interact
  • The service requestor invokes or initiates an
    interactions with the service.
  • Single Message One Way, Broadcast, Multi Message
    conversation, etc.
  • Synchronous or Async.

20
Extended Architecture
  • Extends the basic architecture with additional
    features and functionality, extending the
    technologies and Components.

21
Extended Architecture (Cont.)
  • List of Features (Partial)
  • A sync. Messaging
  • Attachments packaging of multiple docs
    together, binary data, etc. (SOAP with
    Attachments and DIME)
  • Caching
  • Long running transactions
  • Message Authentication HTTP auth, x.509

22
Extended Architecture (Cont.)
  • List of Features (Partial)
  • Message Confidentiality SSL/TLS, SOAP
    encryption
  • Message Integrity digital signature with SOAP
  • Management messages
  • Session

23
Web Services Stacks
  • The stack of technologies create the protocol.

24
WS Stacks Wire Stack
  • Wire Stack
  • Encapsulates the concepts and technologies needed
    for the actual, physical exchange of information
    between the roles mentioned before.
  • Network transport
  • Message packaging
  • Message extensions

25
WS Stacks Wire Stack
26
WS Stacks Wire Stack
  • Transport
  • HTTP is the de facto standard network protocol
    for internet available web services.
  • Intranet domains may use MQSeries, CORBA, etc.
  • The choice of network technology can be made
    transparent to the developer and consumer of the
    service

27
WS Stacks Wire Stack
  • Packaging
  • SOAP is the de facto standard for XML messaging.
  • Relatively simple, thin layer on top of existing
    network technologies (HTTP).
  • Extensible, allows solutions to be incrementally
    applied as needed.
  • Based on XML, enjoys a broad support from the
    community
  • More on SOAP later.

28
WS Stacks Wire stack
  • Extensions
  • Provides a framework that allows additional
    information to be attached to WS messages.
  • SOAP defines a mechanism to incorporate
    orthogonal extensions (features).
  • A broad collection of features are already
    standard, and more to come

29
WS Stacks Wire stack
30
WS Stacks Description Stack
31
WS Stacks Description Stack
  • A stack of description documents defined using
    XML Schema.
  • Through the service description a service
    provider communicates all the specifications for
    invoking the web service.
  • Uses WSDL for base level service desc.

32
WS Stacks Description Stack
  • Interface and implementation
  • The messages the service expects and returns, and
    how to encode the messages and where to send them
    to.
  • Minimum service description.

33
WS Stacks Description Stack
  • Policy
  • defines business context, QoS, security req, etc.
  • Presentation
  • how to render the input/output messages on screen
    for different devices/

34
WS Stacks Description Stack
  • The upper levels of this stack are somewhat left
    for the user to guess

35
WS Stacks Discovery stack
36
WS Stacks Discovery stack
  • The discovery stack can be implemented with a
    range of solutions.
  • Service discovery depends on service publication.
  • Any mechanism that allows the service requestor
    to gain access to the service description and
    make it available to the application at runtime
    qualifies as service discovery

37
WS Stacks Discovery stack
  • Publication
  • Several tools exist that help the developer to
    produce the service description.
  • Direct publish send description directl to the
    user (email, ftp, etc)
  • UDDI Registry business context and toxonomies.

38
WS Stacks Discovery stack
  • Discovery and publication
  • Service requestors can retrieve a service
    description at design time or run time, from a
    web page (URL), repository or UDDI registry.
  • The service requestor uses the description to
    create SOAP requests to send to the service.

39
WS Stacks Discovery stack
  • Inspection
  • Inspection technologies such as WSIL provide a
    de-centralized service discovery method
  • Local service discovery for local web service
    applications (micro SOAs that dont leave the
    box all else is the same except it limits where
    it looks for services).
  • Application integration.
  • Discovery agents populated by crawlers looking
    for WSIL documents.
  • Management topologies of available services (but
    its not a discovery source).

40
WS Stacks - Summary
41
Questions
42
Bibliography
  • W3C Web services architecture http//www.w3.org/T
    R/ws-arch/
  • W3C Web Services Glossary http//www.w3.org/TR/ws
    -gloss/
  • Web Services Architecture Usage Scenarios
  • http//www.w3.org/TR/ws-arch-scenarios/
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