XML Web Services
One of the main reasons the web succeeded today is it simplicity due to which it can be omnipresent. Web services are the new generation we applications. They are self starting applications that run on their own platforms and are accessible on the web easily. Web services architecture is very simple to understand and is divided into tiers.
What is a web service platform?
A basic web service platform is XML or Extensible Markup Language. XML or the Extensible Markup language is a meta-language which allows you to compose languages in it to develop an interface between the client and the service. This technology works with the help of a middle ware; the XML converts the data to a middleware request and then converts it back to XML.
What are the various platforms?
The various web services with web platforms are XML plus HTTP, XML plus Soap, XML plus UDDL, XAML, XMS, XLANG and the XKMS respectively.
SOAP: SOAP or the Simple Object Access Protocol is used mainly to exchange web based messages between computer networks. It is a protocol that performs Remote Procedure Calls (RPC). SOAP is being further developed by the W#C workgroup which maintain the group of protocols that work with the Extensible Markup Language. SO presently SOAP is not being used and is kept at bay for further research.
UDDI: UDDI or the Universal Description, Discovery and Integration Service are a dynamic protocol used along with the Extensible markup language to find other web services on the internet. UDDI’s functionalities are very similar to the CORBA and also act as a Domain Name Server for service for various business applications. The UDDI is dependant on the SOAP in a way that the UDDI sends requests disguised as SOAP messages. It is still not accepted as a standard protocol for XML because of its limitations in terms of dependency on SOAP which itself is under scrutiny and undergoing changes.
XLANG: XLANG is an extension of WSDL or the Web Services Description Language. WSDL is a XML based service which helps the communication between web services. XLANG service is also used to undo some complex operations. In fact the main usage of this protocol is to undo the operations which are very important form the commercial aspect of these applications.
XAML: Transaction Authority Markup Language acts as a compensatory language for the XLANG. XAML is also a service that is used to undo operations but in this case the XAML does not restrict only to two phased applications like between a buying and paying transaction, or a selling and receiving transaction. It leaves other options open for a two way transaction to be undone.
XKMS: XML Key Management Specification is mainly use to create digital certificates or signatures with XML applications. XKMS is further divided into two services the XKISS and the X-KRSS. The XKMS protocol depends on the XML, WSDL and the SOAP largely.
Since the beginning XML or the Extensible Markup Language has been growing constantly different standards are being asset and different technologies have been evolving. For XML users it may be extremely difficult to keep up with the ever changing spaces and new entries. The word standard has to be redefined when it comes to XML because there are so many standards of usage already and more are being added. However there are some core standards in XML which can be considered as a dictionary of fixed terms. These terms form the basis of what is expressed in the Extensible Markup Language.
Canonical XML or the C14n
Canonical XML allows the creation of XML documents in XML syntax without changing the meaning of syntax or causing any syntax errors and creates a representation of the XML document physically. This is a standard method of creating a physical representation of an XML document.
XML processors find information on how to resolve a URL in a XML catalog. It also has the capability of substituting one resource with the other. Catalog processing is an integral part of the XML parsing.
XML information set or the Infoset
XML information set enables to list an XML document in as series of objects or in a series of descriptions that have specialized properties. This series also provides information on the XML document.
XML Name spaces
XML namespaces enables the users to provide universal names attributes for elements in an XML document. For example namespaces like head and body can be used which are otherwise used to describe anatomy of a human body.
RELAX NG is a kind of language editor which can be used to describe, define and also provide limitations for XML language. It is a grammar based schema language. Schema means something which can be used to limit and define terms in language.
Schematron is also a schema language but it is a rules based language. It just creates rule and not limitations. These rules define and limit the XML language.
DSDL or Document Schema Definition Languages
Document Schema Definition Languages or the DSDL provides a framework for the validation and core processing of Extensible Markup Language. It contains individual specifications ether in small groups or in experts and they are all well defined. The DSDL framework of specifications can be used separately or collectively for XML validation.
Uniform Resource Identifiers (URL) and International Resource Identifiers (IRI)
The Uniform Resource Identifiers is a tool used to identify resources that are of HTTP, XML, and Multimedia in nature. International Resource Identifiers are tools used to locate URL’s, XML documents, http documents from the international resources on the internet.
W3C XML Schema
W3C XML schema is one of the schema languages to define and limit the XML language. It also forms the foundation for a few standards in XML message or data binding.
XML Inclusions or Include
XML Inclusions or XInclude has the capability of including or merging all XML documents and also ahs added features. One large document can be merged with smaller ones.
XML Linking Language or XLink
XML Linking language or XLink is a framework which enables a facility to create links in a XML document. It is used to create simple links which are essential for XML documents.
XML base or the Extensive Markup Language Base is the tools which enables the merging of ML elements with the URI’s or the Universal resource Identifiers and the IRI"S or the International Resource Identifiers. It provides a platform where these both the XML documents and the URI’s and IRI’s can associate with each other.
XML ID provides an environment for expressing the unique identifiers and attributes which are used to identify the elements of the XML document.
XML or Extensible Markup Language
The XML or the Extensible Markup Language is a derivation of the SGML or the Standard Generalized Markup Language. While the SGML was a very rigid format the XML is a much more relaxed environment to work with.
XML Path Language or the XPath
XPath is considered to be the most successful of all the XML technologies today. It forms syntax or a data model to identify different parts of XML document.
X Pointer Framework
The XPointer Framework refers to the fragments and their locations in a XML document. It brings similar URL’s which use hashes to point a particular link of a HTML document together.
Apart from the standards for XML documents there are some XML processing standards like the Cascading Style sheets, Document Object model, Remote Events for XML, Simple API for XML, State Chart XML, SOAP, SQL with XML extensions, XML Binding Language, XForms, XML Processing Model and the Extensible stylesheet Language Transformations (XSLT).
Some of the key XML vocabularies are
- Atom Syndication Format, Darwin
- Information Typing Architecture (DITA), DocBook, Mathematical Markup
- Language (MathML), Open Document Format for Office Applications (Open
- Document), Resource Description Framework (RDF), Synchronized
- Multimedia Integration Language (SMIL), Scalable Vector Graphics
- (SVG), Voice Extensible Markup Language (VoiceXML), XML Bookmark
- Exchange Language (XBEL), XHTML, XQuery 1.0: An XML Query Language,
- Extensible Stylesheet Language Formatting Objects (XSL-FO), XUpdate
Several organizations have been involved in creating standards for an XML document for the XML users like the World Wide Web consortium which is also commonly referred to as W3C an they usually issue recommendations rather than standards. Another of these is the International Organization for Standardization which probably leads the others and the most of active of all.
Organization for the Advancement of Structured Information Standards (OASIS) has its own standards and has been approved and recommended by the Oasis team. The last is the Internet Engineering task Force is an organization which thrives on public opinion gathered from collecting reviews over the Internet. They collect Internet drafts and RFC’s or Request for Comment, almost anyone with a computer and Internet can submit the RCF or the Internet Draft and voice their opinions.
The XML community has gained tremendous mileage in the past for its activities in spite of its varying standards and shortcomings it has remained a huge success.