XML Schema Applications

XML Schema provides the separation of document structure and semantics that makes XML such a powerful language for a wide variety of uses.

Data Validation

XML Schemas define the structure of elements and attributes within an XML document, and offer a great deal of flexibility in designing and customizing content models for any kind of documentation requirements. XML parsers use XML Schema to validate the following aspects of XML instances:

  • Document structure, or syntax
  • Datatypes
  • Inclusion of required elements/attributes

This enables application designers to automate the control of user input in any of the many situations where XML is used including Web forms, publishing systems, databases and other backend storage mechanisms, data integration applications, Web services, etc.

Content Model Definition

XML Schema provides a powerful solution for modeling content based on a wide degree of variables. With extended support for both primitive and derived datatype definitions as well as user-defined types, XML Schema gives an enormous amount of flexibility to data modeling, applying programming concepts like inheritance and subclassing to data syntax. This gives content architects the ability to build extended models based on abstract components, and streamlines processes in large-scale documentation projects.

Data Exchange / Integration

XML Schema enables developers to define extensible document structures for XML data. Because XML Schema documents are based on XML syntax, they are programmatically accessible to developers and can add an enormous amount of flexibility to system architectures. XML Schemas can be stored along with other XML documents in XML architectures and data stores and manipulated, referenced, and styled using a growing number of XML companion tools like XPath, XQuery, XInclude/XPointer, and XSL/XSLT.

For example, used in conjunction with other XML technologies, such as XSLT and XML-enabled databases, global elements defined in XSDs can be processed consistently and uploaded to the appropriate database structure or even simultaneously output to HTML, RTF, PDF, and other formats using a methodology called single source publishing.

The data-oriented datatypes provided in XML Schema 1.1, in addition to the document-oriented datatypes in the previous version of the recommendation, facilitate complex document exchange and data integration scenarios, giving it exposure to the B2B and e-commerce architectures that traditionally employ other data formats such as EDI (electronic data interchange).

In addition, XML Schema’s support for namespaces enables XML documents to contain unique identifiers, and therefore incorporate more than one commonly used vocabulary at a time. A namespace declaration, or binding, is generally declared in an XML document via an IRI (Internationalized Resource Identifier), and is expressed by applying a prefix to relevant elements and attributes. Namespaces provide enormous opportunities for data exchange and integration, enabling entire XML frameworks to coexist within the same architecture. This is an extremely valuable asset for a global economy, where mergers and acquisitions, supply chain requirements, and industry standards often dictate heterogeneous data constructs.

Industry XML Standards

Industry XML standards aim to streamline and provide a basis for industry-wide data integration. Implementing a common XML vocabulary enables business partners to seamlessly exchange data across different systems and architectures. XML Schema provides a flexible and extremely portable method for defining these standards and has been used across an ever-growing number of industries including retail, telecommunications, financial services, human resources, healthcare, insurance, e-learning, and printing and publishing.

Global data integration based on XML documentation, exchange, and infrastructure standards seems, however, to be a long way off. Compliance is usually voluntary, and there are often several different industry-specific standards to choose from. In addition, many of these specifications are still evolving, making it business and technology decisions increasingly difficult.

Despite these hurdles, the ability to create a flexible and extensible architecture provided by XML Schema and other XML technologies enables early adopters and forward thinking companies to easily adapt to changing industry mandates with resources such as XSLT, XPath, XQuery, and XML-enabled databases.

There are several key industry standards efforts that have a strong following and are paving the way for data integration and interoperability. These include: DITA, DocBook, SCORM, ACORD, FIXML, cXML, and XBRL.