HOME

TheInfoList




The term Web service (WS) is either: * a service offered by an electronic device to another electronic device, communicating with each other via the
World Wide Web The World Wide Web (WWW), commonly known as the Web, is an information system An information system (IS) is a formal, sociotechnical Sociotechnical systems (STS) in organizational development is an approach to complex organizational ...
, or * a server running on a computer device, listening for requests at a particular port over a network, serving web documents (HTML,
JSON JSON (JavaScript Object Notation, pronounced ; also ) is an open standard An open standard is a standard Standard may refer to: Flags * Colours, standards and guidons * Standard (flag), a type of flag used for personal identification Norm ...
,
XML Extensible Markup Language (XML) is a markup language #REDIRECT Markup language In computer text processing, a markup language is a system for annotation, annotating a document in a way that is Syntax (logic), syntactically distinguishable fro ...

XML
, images). In a Web service a Web technology such as
HTTP The Hypertext Transfer Protocol (HTTP) is an application layer An application layer is an abstraction layer that specifies the shared communications protocols and Interface (computing), interface methods used by Host (network), hosts in a c ...
is used for transferring machine-readable file formats such as
XML Extensible Markup Language (XML) is a markup language #REDIRECT Markup language In computer text processing, a markup language is a system for annotation, annotating a document in a way that is Syntax (logic), syntactically distinguishable fro ...
and JSON. In practice, a web service commonly provides an
object-oriented Object-oriented programming (OOP) is a programming paradigm Program, programme, programmer, or programming may refer to: Business and management * Program management, the process of managing several related projects * Time management * P ...
Web-based interface to a database server, utilized for example by another Web server, or by a
mobile app A mobile application, also referred to as a mobile app or simply an app, is a computer program In imperative programming In computer science, imperative programming is a programming paradigm that uses Statement (computer science), statements t ...
, that provides a user interface to the end-user. Many organizations that provide data in formatted HTML pages will also provide that data on their server as XML or JSON, often through a Web service to allow
syndication Syndication may refer to: * Broadcast syndication, where individual stations buy programs outside the network system * Print syndication, where individual newspapers or magazines license news articles, columns, or comic strips * Web syndication, w ...
, for example, Wikipedia's
Export An export in international trade International trade is the exchange of capital, goods, and services across international borders or territories because there is a need or want of goods or services. In most countries, such trade rep ...
. Another application offered to the end-user may be a mashup, where a Web server consumes several Web services at different machines and compiles the content into one user interface.


Web services (generic)


Asynchronous JavaScript And XML

Asynchronous JavaScript And XML (AJAX) is a dominant technology for Web services. Developing from the combination of HTTP servers, JavaScript clients and
Plain Old XMLPlain Old XML (POX) is the basic XML, sometimes mixed in with other, blendable specifications like XML Namespaces, Dublin Core, XInclude and XLink. This contrasts with complicated, multilayered XML specifications like those for web services or Re ...
(as distinct from
SOAP Soap is a salt (chemistry), salt of a fatty acid used in a variety of cleansing and lubricating products. In a domestic setting, soaps are surfactants usually used for washing, bathing, and other types of housekeeping. In industrial settings, ...

SOAP
and W3C Web Services), now it is frequently used with
JSON JSON (JavaScript Object Notation, pronounced ; also ) is an open standard An open standard is a standard Standard may refer to: Flags * Colours, standards and guidons * Standard (flag), a type of flag used for personal identification Norm ...
as well as, or instead of, XML.


REST

Representational State Transfer (REST) is an architecture for well-behaved Web services that can function at Internet scale. In a 2004 document, the W3C sets following REST as a key distinguishing feature of Web services:


Web services that use markup languages

There are a number of Web services that use markup languages: * JSON-RPC. *
JSON-WSP JSON-WSP is a web service protocol that uses JSON for service description, requests and responses. It is inspired from JSON-RPC, but the lack of a service description specification with documentation in JSON-RPC sparked the design of JSON-WSP. The ...
* Representational state transfer (REST) versus
remote procedure call#REDIRECT remote procedure call In distributed computing, a remote procedure call (RPC) is when a computer program causes a procedure ( subroutine) to execute in a different address space (commonly on another computer on a shared network), which is ...
(RPC) *
Web Services Conversation Language The Web Service Conversation Language (WSCL) proposal defines the overall input and output message sequences for one web service The term Web service (WS) is either: * a service offered by an electronic device to another electronic device, communi ...
(WSCL) *
Web Services Description Language The Web Services Description Language (WSDL ) is an XML-based interface description language An interface description language or interface definition language (IDL), is a specification language used to describe a Component-based software engineeri ...
(WSDL), developed by the
W3C The World Wide Web Consortium (W3C) is the main international standards organization A standards organization, standards body, standards developing organization (SDO), or standards setting organization (SSO) is an organization whose primary f ...
*
Web Services Flow LanguageWeb Services Flow Language 1.0 (WSFL) was an XML programming language proposed by IBM in 2001 for describing Web service, Web services compositions. Language considered two types of compositions. The first type was for describing business processes a ...
(WSFL), superseded by
BPEL The Web Services Business Process Execution Language (WS-BPEL), commonly known as BPEL (Business Process Execution Language), is an OASIS In geography Geography (from Greek: , ''geographia'', literally "earth description") is a fi ...
*
Web template A web template system in web publishing lets web designers and developers work with ''web templates'' to automatically generate custom web pages, such as the results from a search. This reuses static web page elements while defining dynamic eleme ...
*
WS-MetadataExchangeWS-MetaDataExchange is a web service The term Web service (WS) is either: * a service offered by an electronic device to another electronic device, communicating with each other via the World Wide Web upright=1.35, A global map of the web ind ...
*
XML Interface for Network Services XML Interface for Network Services (XINS) is an open-source technology for definition and implementation of internet applications, which enforces a specification-oriented approach. Specification-oriented approach The specification-oriented appro ...
(XINS), provides a POX-style web service specification format


Web API

A
Web API A web API is an application programming interface In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processes and devel ...

Web API
is a development in Web services where emphasis has been moving to simpler representational state transfer (REST) based communications. Restful APIs do not require XML-based Web service protocols (
SOAP Soap is a salt (chemistry), salt of a fatty acid used in a variety of cleansing and lubricating products. In a domestic setting, soaps are surfactants usually used for washing, bathing, and other types of housekeeping. In industrial settings, ...

SOAP
and WSDL) to support their interfaces.


W3C Web services

In relation to W3C Web services, the
W3C The World Wide Web Consortium (W3C) is the main international standards organization A standards organization, standards body, standards developing organization (SDO), or standards setting organization (SSO) is an organization whose primary ...

W3C
defined a Web service as: W3C Web Services may use SOAP over HTTP protocol, allowing less costly (more efficient) interactions over the Internet than via proprietary solutions like EDI/B2B. Besides SOAP over HTTP, Web services can also be implemented on other reliable transport mechanisms like
FTP The File Transfer Protocol (FTP) is a standard communication protocol used for the transfer of computer files from a server to a client on a computer network. FTP is built on a client–server model architecture using separate control and data c ...
. In a 2002 document, th
Web Services Architecture Working Group
defined a Web services architecture, requiring a standardized implementation of a "Web service."


Explanation

The term "Web service" describes a standardized way of integrating Web-based applications using the
XML Extensible Markup Language (XML) is a markup language #REDIRECT Markup language In computer text processing, a markup language is a system for annotation, annotating a document in a way that is Syntax (logic), syntactically distinguishable fro ...

XML
, SOAP, WSDL and UDDI open standards over an
Internet Protocol The Internet Protocol (IP) is the network layer In the seven-layer OSI model The Open Systems Interconnection model (OSI model) is a conceptual model A conceptual model is a representation of a system, made of the composition of concept C ...
backbone. XML is the data format used to contain the data and provide metadata around it, SOAP is used to transfer the data, WSDL is used for describing the services available and UDDI lists what services are available. A Web service is a method of communication between two electronic devices over a network. It is a software function provided at a
network address A network address is an identifier for a node In general, a node is a localized swelling (a "knot A knot is an intentional complication in Rope, cordage which may be practical or decorative, or both. Practical knots are classified by function, ...
over the Web with the service ''always-on'' as in the concept of utility computing. Many organizations use multiple software systems for management. Different software systems often need to exchange data with each other, and a Web service is a method of communication that allows two software systems to exchange this data over the Internet. The software system that requests data is called a ''service requester'', whereas the software system that would process the request and provide the data is called a ''
service provider A service provider (SP) provides organizations with consulting, legal, real estate, communications, storage, processing. Although a service provider can be an organizational sub-unit, it is usually a third party or outsourced supplier, including tel ...
''. Different software may use different programming languages, and hence there is a need for a method of
data exchange Data exchange is the process of taking data structured under a ''source'' schema and transforming it into a ''target'' schema, so that the target data is an accurate representation of the source data.A. Doan, A. Halevy, and Z. Ives.Principles of da ...
that doesn't depend upon a particular programming language. Most types of software can, however, interpret XML tags. Thus, Web services can use XML files for data exchange. Rules for communication different systems need to be defined, such as: * How one system can request data from another system. * Which specific parameters are needed in the data request. * What would be the structure of the data produced. (Normally, data is exchanged in XML files, and the structure of the XML file is validated against a .xsd file.) * What error messages to display when a certain rule for communication is not observed, to make
troubleshooting Troubleshooting is a form of problem solving Problem solving consists of using generic or ad hoc Ad hoc is a List of Latin phrases, Latin phrase meaning literally 'to this'. In English, it generally signifies a solution designed for a sp ...

troubleshooting
easier. All of these rules for communication are defined in a file called
WSDL The Web Services Description Language (WSDL ) is an XML-based interface description language An interface description language or interface definition language (IDL), is a specification language used to describe a Component-based software engineeri ...
(Web Services Description Language), which has a .wsdl extension. (Proposals for Autonomous Web Services (AWS) seek to develop more flexible Web services that do not rely on strict rules.) A directory called
UDDI Web Services Discovery provides access to software systems over the Internet using standard protocols. In the most basic scenario there is a ''Web Service Provider'' that publishes a service and a ''Web Service Consumer'' that uses this service. W ...
(Universal Description, Discovery, and Integration) defines which software system should be contacted for which type of data. So when one software system needs one particular report/data, it would go to the UDDI and find out which other systems it can contact for receiving that data. Once the software system finds out which other systems it should contact, it would then contact that system using a special protocol called
SOAP Soap is a salt (chemistry), salt of a fatty acid used in a variety of cleansing and lubricating products. In a domestic setting, soaps are surfactants usually used for washing, bathing, and other types of housekeeping. In industrial settings, ...

SOAP
(Simple Object Access Protocol). The service provider system would first validate the data request by referring to the WSDL file, and then process the request and send the data under the SOAP protocol.


Automated design methods

Automated tools can aid in the creation of a Web service. For services using WSDL, it is possible to either automatically generate WSDL for existing classes (a bottom-up model) or to generate a class skeleton given existing WSDL (a top-down model). * A developer using a bottom-up model writes implementing classes first (in some programming language) and then uses a WSDL generating tool to expose methods from these classes as a Web service. This is simpler to develop but may be harder to maintain if the original classes are subject to frequent change. * A developer using a top-down model writes the WSDL document first and then uses a code generating tool to produce the class skeleton, to be completed as necessary. This model is generally considered more difficult but can produce cleaner designs and is generally more resistant to change. As long as the message formats between the sender and receiver do not change, changes in the sender and receiver themselves do not affect the Web service. The technique is also referred to as ''contract first'' since the WSDL (or contract between sender and receiver) is the starting point. * A developer using a Subset WSDL (SWSDL) (i.e. a WSDL with the subset operation in the original WSDL) can perform Web service testing and top-down development.


Criticism

Critics of non-RESTful Web services often complain that they are too complex and based upon large software vendors or integrators, rather than typical
open source Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use the source code, design documents, or content of the product. The open-source model is a decentralized softwa ...
implementations. There are also concerns about performance due to Web services' use of XML as a message format and SOAP/HTTP in enveloping and transporting.


Regression testing of Web services

Functional and non-functional testing of Web services is done with the help of WSDL parsing.
Regression testing Regression testing (rarely ''non-regression testing'') is re-running functional testing, functional and non-functional testing, non-functional tests to ensure that previously developed and tested software still performs after a change. If not, tha ...
is performed by identifying the changes made to upgrade software. Web service regression testing needs can be categorized in three different ways, namely, changes in WSDL, changes in the code, and selective re-testing of operations. We can capture the above three needs in three intermediate forms of Subset WSDL, namely, Difference WSDL (DWSDL), Unit WSDL (UWSDL), and Reduced WSDL (RWSDL), respectively. These three Subset WSDLs are then combined to form Combined WSDL (CWSDL) that is further used for regression testing of the Web service. This will help in Automated Web Service Change Management (AWSCM), by performing the selection of the relevant test cases to construct a reduced test suite from the old test suite. Web services testing can also be automated using several test automation tools like SOAP UI, Oracle Application Testing Suite (OATS),Web Services Testing using Oracle Application Testing Suite
/ref> Unified Functional Testing, Selenium, etc.


Web service change management

Work-related to the capture and visualization of changes made to a Web service. Visualization and computation of changes can be done in the form of intermediate artifacts (Subset WSDL). The insight on the computation of change impact is helpful in testing, top-down development and reduce regression testing. AWSCM is a tool that can identify subset operations in a WSDL file to construct a subset WSDL.


See also

* List of Web service frameworks * List of Web service protocols *
List of Web service specificationsThere are a variety of specifications associated with web services. These specifications are in varying degrees of maturity and are maintained or supported by various standards bodies and entities. These specifications are the basic web services fram ...
*
Middleware Middleware is a type of computer software Software is a collection of instructions that tell a computer A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations automatically. Modern com ...

Middleware
*
Service-oriented architecture In software engineering Software engineering is the systematic application of engineering approaches to the software development, development of software. A software engineer is a person who applies the principles of software engineering to desig ...
(SOA) *
Web Map Service A Web Map Service (WMS) is a standard protocol developed by the Open Geospatial Consortium The Open Geospatial Consortium (OGC), an international voluntary consensus standards organization A standards organization, standards body, standards de ...


Notes


References


External links


Messaging Design Pattern
documentation a
SOA Patterns
* Th
Web Services Activity
page at
W3C The World Wide Web Consortium (W3C) is the main international standards organization A standards organization, standards body, standards developing organization (SDO), or standards setting organization (SSO) is an organization whose primary ...

W3C

Web Services Architecture
the W3C Working Group Note (11 February 2004)
Investigating Web Services on the World Wide Web
the analysis presented at the WWW2008 conference
Guide to Secure Web Services
(SP 800-95) at
NIST The National Institute of Standards and Technology (NIST) is a physical sciences Physical science is a branch of natural science that studies abiotic component, non-living systems, in contrast to life science. It in turn has many branches, e ...
{{DEFAULTSORT:Web Service Web services