A Service Web is a computer program allowing the communication and the exchange of information between heterogeneous applications and systems in distributed environments. It is thus about a whole of functionalities exposed on Internet or a Intranet, by and for applications or machines, without human intervention, and in real-time .

There exist several technologies behind the term Services Web :

• the Services Web of the type REST entirely expose these functionalities like a whole of resources (URI) identifiable and accessible by syntax and semantics from the protocol HTTP. The Services Web of the type REST are thus based on the architecture of the basic Web and its standards: HTTP and URI.

• the Services Web *** remotely expose these same functionalities in the form of achievable services. Their specifications rest on the standards SOAP and WSDL to transform the problems of integration inherited the world Middleware into objective of interworking. The standards *** are often décriés like were their ancestors CORBA, RMI or DCOM: complex technologies inherited the old principle RPC, strongly coupled and with difficulty intéropérables in heterogeneous environments. A contrario, the Web is by nature a platform intéropérable.

The Services Web of the type REST

Introduction

The World Wide Web is a application conceived according to architecture REST. The architecture of the Web thus replaces the concepts applicatifs customers and waiters by the concepts agents and resources . Agents interact with resources to create, reach, modify or remove a resource. Until now, one spoke especially about the interaction between user agents , mainly the navigators with the resources.

Today, one speaks more and more about the interaction between agents resources ; i.e. the relation between the resources: a resource becomes the agent of another resource, but remains itself a resource accessible by other agents. It is exactly the architecture described by the example of applicative implementation of the Mashups. The Services Web thus treat agents resources where the traditional procedure of the Web speaks about user agents. but the two concepts rest on same architecture: REST

There are not thus basic differences between the interaction of a navigator with a resource and that of a Service Web with a resource. The principal difference is at the level of the format of the representation of the data: HTML for the navigators or user agents, XML or JSON for the Services Web or agents resources…

One can thus define a Service Web like the implementation software of a resource, identified by a URL, and accessible by using protocols Internet. The agents deal with the contents, of the representation of their state, not of the type of contents. It is thus necessary to see the Services Web like the means of handling information, and not like a simple service provider.

Denominations

• Services Web RESTful
• Agents Resources
• Software Robots

The Services Web ***

Introduction

The Services Web *** indicate the software implementation of the specifications *** and rest all on a whole of protocols and basic standards used for the exchange of information between application S in heterogeneous environments:

• the protocol SOAP for the exchange of messages.

• the file WSDL for the description of the messages, their type of data…
• a possible entry in a directory UDDI

These Services Web *** are in addition defined according to the type of architecture SOA

The software written in various Computer programming languages and on various platforms can employ Services Web *** to exchange data through Data-processing networks like Internet. The OASIS and the World Wide Web Consortium (W3C) are the coordination committees responsible for the architecture and the standardization of the Web services. To improve interworking between the achievements of service Web, the organization WS-I developed a series of profiles to make evolve/move the future implied standards.

Used standards

• List of the specifications of the Services Web ***

Advantages

• the Web services provide the interworking between various Logiciel S functioning on various platforms.
• the Web services use standard and open protocols.
• the protocols and the Formats of data are with the format text as far as possible, thus facilitating the comprehension of the total operation of the exchanges.
• Based on the protocol HTTP, the Web services can function through many Avoid-fires without requiring changes on the rules of filtering.

Disadvantages

• the standards of Web services in certain fields are currently recent.
• the Web services suffer from weak performances compared with other approaches of the data processing distributed such as the RMI, CORBA, or DCOM.
• By the use of the protocol HTTP, the Web services can circumvent the security measures installation through the Firewall S .

Scenarios

The Web services implement logic trade made consumable (one consumes a service Web ⇒ to use) by the use of standards (mainly TCP/IP, URI/URN/URL, MIME, HTTP/smtp /.. , SOAP, SSL/TLS,… for transport, then XML for the contents), which allows any technology using these standards of being able to exploit it, thus facilitating the Interopérabilité applications.

The creation of Web services is justified by orientated architecture service, i.e. the will to make available a service which implements a logic trade hidden with users.

Within the framework of contracts of exchange of information in Business to Business (undertaken ↔ undertaken), as in Business to Consumer (undertaken ↔ customer/user), another interest for which Web services are employed is the fact that they are based on the protocol HTTP (which uses port 80 per defect). To include/understand this, keep in mind that many companies were protected by employing Firewall S which filter and block much traffic of Internet for safety reasons. In this medium, much of (almost all them) ports are closed with the traffic inbound and leaving and the administrators these firewalls are not eager to open them. Port 80, however, is always open because it is employed by the protocol HTTP used by the Navigateurs Web. With this advantage, the services Web represent a kind of Tunneling.

Platforms

Web services can be deployed by employing a software of Serveur of application:

• JAX-WS 2.x which constitutes the implementation of reference of Java EE is Open Source and integrated in GlassFish and usable in other environments. Its extension WSIT (so called " Project Tango") propose an implementation of WS-ReliableMessaging, WS-SecureConversation, WS-Trust,…

• Axis and the waiter of Jakarta Tomcat (two projects Open source of Apache Software Foundation)
• XFire of CodeHaus offers a framework Java with an approach different of Axis: http://xfire.codehaus.org/
• ColdFusion MX of Macromedia
• Waiters HTTP IIS of Microsoft (with the framework .NET)
• WebLogic of BEA
• WebSphere Application Server of IBM (based on the waiter of Apache and the platform of J2EE)
• Oracle Waiter Application of Oracle Corporation
• ZenWorks of Novell
• Library for the developers of services Web in NuSOAP
• gSOAP: library for the developers of services Web in c++
• JBoss Server Application of the JBoss company. Component of the JEMS (JBoss Enterprise Middleware System) of which also formed part the framework of relational Persistence Hibernate.

See too

Internal bonds

• REST
• Service Oriented Structures (SOA)
• XML
• Simple Object Access Protocol (SOAP)
• Web Services Description Language (WSDL)
• AJAX, or Asynchronous JavaScript And XML
• Smart customer

External bonds

• http://ws.apache.org/axis/ Project Apache Axis .
• http://ws.apache.org/axis2/ Project Apache Axis2 .
• http://jax-ws.dev.java.net JAX-WS 2.x .
• http://msdn2.microsoft.com/fr-fr/webservices/default.aspx Microsoft .
• http://www.w3.org/2002/ws/ W3C .
• http://www.ws-i.org/ WS-I .

Random links:

Nicolas Perrot d' Ablancourt | Approximation of the continuous mediums | Stygie | Aude Gros To bleat | Rene Taveneaux