2.7 XML Standards at a Glance

The various standard building blocks covered in this chapter are summarized in Table 2.5. For each of these standard building blocks, we give a brief summary of their role in the overall XForms architecture.

We conclude this chapter with a brief summary of existing implementations of the various standard building blocks described in this chapter in Table 2.6. This serves to illustrate the advantages resulting from designing XForms based on existing standards. XForms implementations can be put together using the implementations of these building blocks in much the same manner as the XForms specification itself.

Table 2.5. XML Standards at a Glance

Standard	Role in XForms
XML	Encapsulates structured instance data. XML DOM provides underlying model. Serialized instance data is I18N ready.
Namespaces	Partition space of element and attribute names . Enable different XML vocabularies to coexist. Create modular XForms applications. Key to integrating XForms into XML host languages.
Schema	Enables object-oriented descriptions of XML. Provides rich set of data types. Enables off-the-shelf validation. Captures static constraints in the model.
XPath	Locators address portions of an XML instance. Locators used to bind controls to the model. Locators used to bind model properties. A side-effect free expression language. Expresses dynamic properties within XForms.
DOM2	Cross-platform API for eventing . Used to attach behavior . Enables hosting XForms processors in a browser.
XML Events	XML access to DOM2 Events. Defines common XML markup for eventing. Attaches event handlers in XForms documents. Enables declarative authoring in place of scripts.

Table 2.6. Implementations of Relevant W3C Standards

Standard	Implementation
XML Schema	Apache xerces on all platforms MSXML.dll on Windows
XPath	Apache Xalan on all platforms Mozilla on all platforms MSXML.dll on Windows
DOM2 events	Mozilla on all platforms Internet Explorer
XML Events	Apache xerces on all platforms All XForms implementations
XForms	X-Smiles ”an open source XML browser FormsPlayer ”an XForms plug-in for IE Novell XForms technology preview IBM XForms technology preview for Mozilla and IE