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XML Schema Interfaces

Extensible Markup LanguageExtensible Markup Language (XML) plays an important role in the exchange of a wide variety of data via the Web or other means. Interfacing is the most important aspect to conducting Web business, and how easily it can be carried out is a major concern of businesses today. This article touches upon the various advantages of using XML Schema Interfaces, and why Application Developers should support schema design. XML Schemas describe and specify the structure, grammar, and restriction over data in an XML document, this language is also referred to as XML Schema Definition (XSD). The purpose of an XML Schema is to communicate shared vocabularies by allowing devices to execute rules developed by people. In 2001, the World Wide Web Consortium (W3C) approved XML Schema as an official recommendation.

With the use of a standards-based format that is flexible, XML offers a significant advantage in how data is described and exchanged by Web-based applications. XML Schemas are an area of XML syntax that in some ways are comparable to DTDs (Document Type Definition). DTDs were the original way in which to specify the grammar for an XML file format. They are less complex than XML Schema documents and pose many disadvantages. An XML Schema is a key component or XML-based alternative to DTDs, only more powerful. XML Schemas evolved as a way of providing rich data typing capabilities for elements and attributes as well as providing Object-oriented design principles.


One of the advantages XML Schemas have over DTDs is the support of a larger variety of data types. With this type of support, it is easier to define data restrictions and patterns, convert and validate the data, describe allowable document content, and use data from databases. XML Schemas also allow documentation from schemas to define column labels or tags within interface devices, and have the ability to move documentation into the schema itself. The use of an extensible Schema definition permits the creation of other data types, the reuse of the Schema in other Schemas, and the ability to reference multiple Schemas in the same document.

An XML structure describes the interface of a programmatic class, and the discovery of computer application classes become possible with Simple Object Access Protocol (SOAP). XML Schemas can also be queried and manipulated by XSLT to generate an instance of data from its associated schema generically. The ability to have Dynamic and Auto-Schemas are other advantages over DTDs.

From a developers’ standpoint, XML Schemas are easy to create, and provide rich data typing capabilities for elements and attributes. Although XML has stringent syntax rules, well-formed documents can still contain errors, and with an XML Schema most errors can be found with validating software. The ability to use an XML editor and parser on your Schema files, and transform your Schema with XSLT is considered a great benefit. Another plus, is not having to learn a new language, and having the ability to manipulate a Schema with the XML DOM.

XML Schemas can secure data communication with the use of namespaces, which can define data types without the worry of name collisions. When data is being transferred, it is crucial that both parties (sending/receiving) share the same content expectations. XML Schemas allow the sender to subscribe the data in which the receiving end will understand. A Schema also enables the concept of primitive libraries that could reside anywhere on the net.

Since the overall purpose of XML Schemas is to provide a means in which to validate XML documents with the use of rules, in the future, Schemas could be used for legal documents, XSLT transformations (changing it from a text manipulation language to a data manipulation language), or by providing Schema variants, XSD could make it possible to have several transformations for providing flexibility into the B2B sphere.

As you have read, Schemas provide a means of defining the structure, content, and semantics of XML documents which can be shared amongst documents, databases, and computers alike. The use of XML Schemas and XML Schema Interfaces are a very important part of the future, and designing and developing applications that make use of this flexible concept is advantageous to all.

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