What is Web Service – Complete Guide | Part 2

What is Web Service – Complete Guide | Part 2

Web Services – Technologies Used

For the representation and structuring of data in messages received / sent is used XML (eXtensible Markup Language). Calls to operations, including input / output, are encoded in SOAP (Simple Object Access Protocol, XML-based). Services (operations, messages, parameters, etc..)

Are described using WSDL (Web Services Description Language). The process of publication / research / discovery of Web services using the UDDI (Universal Description, Discovery and Integration).

XML (Extensible Markup Language)

Extensible Markup Language (XML) is the basis on which Web services are built. XML provides the description, storage, transmission format for exchanging data through Web Services and also to create Web Services technologies to exchange data.

The syntax of XML technologies used in Web Services specifies how data is represented generally defines how and with what qualities of service data is transmitted, details how the services are published and discovered. Web Services decode the various parts of XML to interact with various applications.

SOAP (Simple Object Access Protocol)

SOAP (Simple Object Access Protocol) is based on a remote invocation of a method and this needs to specify the address of the component, the method name and arguments to this method. These data are formatted in XML with certain rules and sent normally over HTTP for this component. Does not define or impose any semantics, whether the programming model, whether the semantics of specific implementation.

This is extremely important because it allows either the service or the client that invokes the service are applications built on different programming languages. For this reason, SOAP has become an accepted standard to be used with Web Services, a technology built on XML and HTTP.

Thus, it is intended to ensure interoperability and intercommunication between different systems through the use of XML and HTTP transport mechanism or another, for example, SMTP. SOAP allows XML documents, sending and receiving on the Web supporting a common protocol for transferring data to an effective communication network, i.e., SOAP provides transportation data to Web Services.

Regarding the Web, SOAP is an RPC protocol that runs over HTTP (or SMTP, or other) in order to overcome the constraints of security / firewalls usually imposed on the classical RPC (RMI, DCOM, CORBA / IIOP) supporting XML messages. Instead of using HTTP to request an HTML page to be viewed in a browser, sends a SOAP message using the XML HTTP request and receives a response, if any, through the HTTP response. To ensure smooth transmission of XML message, the HTTP server such as Apache or IIS (Microsoft Internet Information Server) receives SOAP messages and to validate and understand the format of the XML document defined in the SOAP v1.1 specification.

WSDL (Web Services Description Language)

It stands for Web Services Description Language, XML-based standard for describing the service as in COM, where he brings up the Web service methods. It functions as a kind of “TypeLibrary” Web service, and is used to validate the method calls.

The WSDL (Web Services Description Language) is a specification developed by W3C that describes the Web Services according to an XML format.

WSDL is extensible to allow description of services and their messages regardless of message formats and network protocols that are used. However, it is common to use the MIME (Multipurpose Internet Mail Extensions) and HTTP: / / SOAP.

The WSDL describes the services available to the network through a semantic XML, this provides the necessary documentation to be called a distributed system and the procedure required for this communication is established. While SOAP specifies the communication between a client and a server, the WSDL describes the services offered.

UDDI (Universal Description Discovery and Integration)

Protocol developed for organizing and registering Web services. The UDDI (Universal Description Discovery and Integration) is an initiative currently under development through industrial consortium of UDDI was originally promoted by IBM, Microsoft and Arriba, aiming to accelerate the interoperability and use of Web services, the proposal for a name registration service organizations and service description.

A UDDI registry contains three types of information:

  • General information of each organization, such as name, address, and phone contacts;
  • Information services for organizations and business categories;
  • Technical information about the services provided by organizations.

UDDI provides three main functions, known as publication, discovery and connection:

1) Posted: allows an organization to disclose (s) your service (s) (s),

2) discovery: Allows the customer service, Find a service,

3) connection (bind): Allows the customer service, can connect and interact with the service.

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It is the consortium that ensures the integration of Web Services to always ensure that Web Services can “talk to itself”.

Ongoing Initiatives

The success that Web Services might provide necessarily entails the willingness of the industry by sharing and openness of the processes of standardization and the resulting own specifications. A significant part of this process has been developed under the W3C. However, it should also be noted that other efforts and consortia have been developed, such as UDDI, ebXML, or XML / EDI.

For example, ebXML is an effort sponsored by UN / CEFACT and OASIS, whose aim is to produce a set of specifications to enable e-business collaborations. The ebXML standard can be seen as an extension to feature description, publication and service discovery (defined in the UDDI), to discuss the following issues: how to specify business processes as Web services to identify the participants and their contributions; or trading patterns that exist in the collaboration between participants.

These aspects are treated including the following specifications:

1) schemes for specifying business processes, BPSS (business process specification schema),

2) agreements of cooperation protocols, CPA (collaboration protocol agreement),

3) or profiles of cooperation protocols, CPP (Collaboration protocol profile).

Contribution from companies

The main companies in addition to promote and actively participate in several consortia standards, are incorporating into their own infrastructure development and application support implementation of standards related to Web Services.

Among other important development is the Microsoft platform,. Net, Sun’s “Java ONE (Open Net Environment),” Hewlett-Packard, “e-speak” and IBM, “IBM Web Services.”

Evolution of Web Services — New Business Models

Only time will tell who is right: if the skeptics and conservative, if that risk and achieve the vision. With the concept of Web services perhaps most important is not the technology itself, but a whole discussion around the economic and political factors that may raise this paradigm and business models that may emerge.

It seems natural to the emergence of new doors, not for people to consult and use, but for applications, i.e., for services to register / publish in order to become known, discovered and used. These service portals (technically consists of services UDDI registries and / or ebXML) can be defined at global, regional, business domains for horizontal or vertical.

New Technological Requirements

However and of course, new problems and technology requirements are placed with the concept of Web Services: First, the level of these services and modeling of business processes in which those participating.

Aspects such as service composition, workflow coordination, identification and privacy, security, negotiations, contracts and payments, exception handling, categorization and taxonomies of services, etc.., Should be properly investigated and dealt with that this paradigm can come to present a broad consensus and success.

Web Services — Advantages and Disadvantages

Web Services are models that have emerged for the development of typical applications of electronic business, involving and supporting the establishment of cooperation and negotiation in an open, dynamic and distributed among different partners.

Web services may eventually represent a significant success because there is a significant effort on the part of most industrial partners involved in the standardization of technologies.

The underlying technologies for Web Services (such as HTTP, SOAP, WSDL, UDDI, XML) are open, widely circulated and agreed. On the other hand, there is potential to be a real independence of programming languages (Java, C + +, VB, Delphi, C #), the computer architectures and operating systems, allowing an evolution smoother and economic rationale for this computational model.

However, there is a criticism that demonstrates fear or false hope that investments in web services may ensue. One such criticism relates to the fact that SOAP is less efficient than the existing RPC systems. For example, messages (with their envelopes and description of types) exchanged between the parties are described in text / XML while in the classical RPC is exchanged in binary format.

However, this disadvantage is offset significantly by the ease of interoperability between services, with no known issues of security / firewalls, and the ease of hiding the details of owners of infrastructure support.

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