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Web Service


Ahmed Gamal Ahmed Nile University Bioinformatics Group Web Service Over View Web Service Over View Web Service Over View SOAP defines the protocol by which web ... – PowerPoint PPT presentation

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Title: Web Service

Web Service
  • Ahmed Gamal Ahmed
  • Nile University
  • Bioinformatics Group

  • Web Service Over View
  • SOAP
  • WSDL
  • UDDI

Web Service Over View
  • What are Web services?
  • a standardized way of integrating Web-based
    applications using the XML, SOAP, WSDL and UDDI
    open standards over an Internet protocol
  • XML is used to tag the data
  • SOAP is used to transfer the data
  • WSDL is used for describing the services
  • UDDI is used for listing what services are

Web Service Over View
  • Why there is a need for Web services?
  • Web services' distributed computing model allows
    application-to-application communication.
  • Web services allow different applications from
    different sources to communicate with each other
    without time-consuming custom coding, and because
    all communication is in XML, Web services are not
    tied to any one operating system or programming
  • Because of this level of application
    integration, Web services have grown in
    popularity and are beginning to improve business
    processes. In fact, some even call Web services
    the next evolution of the Web.

Web Service Over View
  • Basic Architecture
  • The basic architecture includes Web services
    technologies capable of
  • Exchanging messages
  • Describing Web services
  • Publishing and discovering Web service

Web Service Over View
  • Service-Oriented Architecture
  • SOA is a specific architectural style that is
    concerned with loose coupling and dynamic binding
    between services. Some critically important
    factors at the heart of SOA are necessary to make
    it work effectively.

Web Service Over View
Web Service Over View
  • Components
  • The Service
  • A service is a software module deployed on
    network accessible platforms provided by the
    service provider.
  • It exists to be invoked by or to interact with a
    service requestor.
  • It may also function as a requestor, using other
    web services in its implementation.

Web Service Over View
  • Components
  • The Service Description
  • The service description contains the details of
    the interface and implementation of the service.
  • This includes its data types, operations, binding
    information, and network location.
  • It could also include categorization and other
    meta data to facilitate discovery and utilization
    by requestors.
  • The service description may be published to a
    requestor directly or to a discovery agency.

Web Service Over View
  • Roles
  • Service Provider
  • From a business perspective, this is the owner
    of the service.
  • From an architectural perspective, this is the
    platform that hosts access to the service.
  • It has also been referred to as a service
    execution environment or a service container.
  • Its role in the client-server message exchange
    patterns is that of a server.

Web Service Over View
  • Roles
  • Service Requestor
  • From a business perspective, this is the business
    that requires certain function to be satisfied.
  • From an architectural perspective, this is the
    application that is looking for and invoking or
    initiating an interaction with a service.
  • The requestor role can be played by a browser
    driven by a person or a program without a user
    interface, e.g. another web service.
  • Its role in the client-server message exchange
    patters is that of a client.

Web Service Over View
  • Roles
  • Discovery Agency
  • This is a searchable set of service descriptions
    where service providers publish their service
  • The service discovery agency can be centralized
    or distributed.
  • A discovery agency can support both the pattern
    where it has descriptions sent to it and where
    the agency actively inspects public providers for
  • Service requestors may find services and obtain
    binding information (in the service descriptions)
    during development for static binding, or during
    execution for dynamic binding.

Web Service Over View
  • Operations
  • Publish
  • In order to be accessible, a service needs to
    publish its description such that the requestor
    can subsequently find it.
  • Where it is published can vary depending upon the
    requirements of the application.

Web Service Over View
  • Operations
  • Find
  • The service requestor retrieves a service
    description directly or queries the registry for
    the type of service required .
  • The find operation may be involved in two
    different lifecycle phases for the service
  • At design time in order to retrieve the service's
    interface description for program development
  • At runtime in order to retrieve the service's
    binding and location description for invocation.

Web Service Over View
  • Operations
  • Interact Eventually, a service needs to be
    invoked. In the interact operation the service
    requestor invokes or initiates an interaction
    with the service at runtime using the binding
    details in the service description to locate,
    contact, and invoke the service. Examples of the
    interaction include single message one way,
    broadcast from requester to many services, a
    multi message conversation, or a business
    process. Any of these types of interactions can
    be synchronous or asynchronous.

Web Service Over View
XMLThe Backbone of Web Services
XMLThe Backbone of Web Services
XMLThe Backbone of Web Services
  • The XML markup, in much the same way as HTML, is
    in the form of tags(e.g., lttaggt, ltnamegt, ltpricegt,
    ltwifegt, and so forth).

XMLThe Backbone of Web Services
  • XML namespaces
  • Name Conflicts
  • In XML, element names are defined by the
    developer. This often results in a conflict when
    trying to mix XML documents from different XML

XMLThe Backbone of Web Services
  • This XML carries HTML table information
  • This XML carries information about a table (a
    piece of furniture)

XMLThe Backbone of Web Services
  • Solving the Name Conflict Using a Prefix
  • Name conflicts in XML can easily be avoided
    using a name prefix.

XMLThe Backbone of Web Services
  • XML Namespaces - The xmlns Attribute
  • When using prefixes in XML, a so-called namespace
    for the prefix must be defined.
  • The namespace is defined by the xmlns attribute
    in the start tag of an element.
  • The namespace declaration has the following
    syntax. xmlnsprefix"URI".

XMLThe Backbone of Web Services
  • The namespace URI is NOT used by the parser to
    look up information.

Web Service Stack
Basic Web Service Usage Scenario
Web Services Implementation
  • Application Server (web service-enabled)
  • provides implementation of services and
    exposes it through WSDL/SOAP
  • implementation in Java, as EJB, as .NET (C)
  • SOAP server
  • implements the SOAP protocol
  • HTTP server
  • standard Web server
  • SOAP client
  • implements the SOAP protocol on the client site

SOAP Simple Object Access Protocol
  • SOAP consists of
  • Envelope construct defines the overall
    structure of messages
  • Encoding rules define the serialization of
    application data types
  • SOAP RPC defines representation of remote
    procedure calls and responses
  • Binding framework binding to protocols such
    as HTTP, SMTP
  • Fault handling
  • Soap supports advanced message processing
  • forwarding intermediaries route messages
    based on the semantics of message
  • active intermediaries do additional
    processing before forwarding messages, may modify

SOAP Simple Object Access ProtocolSOAP Messages
  • SOAP messages consist of
  • Envelope top element of XML message
  • Header general information on message such as
    security (optional)
  • Body data exchanged (required)
  • Header
  • elements are application-specific
  • may be processed and changed by
  • intermediaries or recipient
  • Body
  • elements are application-specific
  • processed by recipient only

SOAP Simple Object Access ProtocolExample
SOAP Message
SOAP Simple Object Access ProtocolProtocol
  • Bindings to different protocols possible HTTP,
  • Different HTTP bindings HTTP POST, HTTP GET
  • standard HTPP POST for request-response

WSDL Web Service Description Language
  • Description of Web services in XML format
  • abstract description of operations and their
    parameters (messages)
  • binding to a concrete network protocol (e.g.
  • specification of endpoints for accessing the
  • Structure of a WSDL document

WSDL Web Service Description Language
Overview of Defining WSDL Services
  • Define in XML Schema the message types used when
    invoking the service MT1, MT2 etc.
  • Define (named) messages by using these types,
  • message m1 has type MT1
  • message m2 has type MT2 etc.
  • Define Services that consist of one or more
    operations each operation is implemented by the
    exchange of messages
  • service S offers operation O1 for executing O1
    first send a request message m1, then a response
    message m2 is returned
  • Define a Binding B to a specific protocol, e.g.
  • service S is implemented in SOAP the SOAP
    messages are constructed from the abstract
    messages m1 and m2 by, e.g. inlining the message
    as body of SOAP messages
  • Service S is provided with binding B at the
    following URI's (called ports)

WSDL Web Service Description Language
Example Overall Document Structure

WSDL Web Service Description Language
Example Definition of Types

WSDL Web Service Description Language
Example Definition of Messages and PortType

WSDL Web Service Description Language
Example Definition of Binding and Service

WSDL Web Service Description LanguagePortTypes
  • WSDL supports 4 message patterns that an endpoint
    (service provider!) can support for an operation
  • one-way message is sent to service provider
    without expecting response
  • request-response request is sent to service
    provider expecting response
  • solicit-response provider sends a message and
    expects response
  • notification message is sent by service provider
  • Message patterns are distinguished by the use of
    input/output elements
  • one way
  • request/response

UDDI Universal Description Discovery and
  • Universal Description and Discovery and
  • UDDI consists of
  • A specification for how to build a registry of
    business, services and how to connect to them
  • A standards committee that is working on revising
    and improving the specification
  • Agreement to operate solutions that conform to
    the specification

UDDI Universal Description Discovery and
  • UDDI Business Registry consist of
  • White pages general information regarding
  • Yellow pages arranged by geography or industry
  • Green pages list protocols supported by each
  • Information stored in XML format
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