Microsoft Office InfoPath is a Microsoft Office System application that is used to create form templates based on Extensible Markup Language (XML) and its associated technologies. XML is an industry-standard language for describing, organizing, and exchanging data. In InfoPath, form templates are based on XML technologies, and form data is saved or submitted in XML format. InfoPath makes use of the following XML technologies:

• XSL Transformation (XSLT) (XSL Transformation (XSLT): A language that is used to transform XML documents into other types of documents, such as HTML or XML. It is designed for use as part of XSL.)
• XML Schemas (XML Schema: A formal specification, written in XML, that defines the structure of an XML document, including element names and rich data types, which elements can appear in combination, and which attributes are available for each element.)
• Extensible Hypertext Markup Language (XHTML) (Extensible Hypertext Markup Language (XHTML): A markup language that extends HTML and reformulates it as XML.)
• XML Path Language (XPath) (XML Path Language (XPath): A language used to address parts of an XML document. XPath also provides basic facilities for manipulation of strings, numbers, and Booleans.)
• Document Object Model (DOM) (Document Object Model (DOM): A World Wide Web Consortium specification that describes the structure of dynamic HTML and XML documents in a way that allows them to be manipulated through a Web browser.)
• XML Signatures (XML Signature: An XML-based digital signature that can be used to help secure the data contained in XML documents. XML Signatures are a standard governed by the World Wide Web Consortium (W3C).)

 Note   You can learn more about these technologies by going to the World Wide Web Consortium (W3C) Web site and searching for each technology.

These technologies are governed by the World Wide Web Consortium (W3C) (World Wide Web Consortium (W3C): A consortium of commercial and educational institutions that oversees research and promotes standards in all areas related to the World Wide Web.), which recommends a specific set of rules, guidelines, and conventions for producing files that are easy to generate and process by different computers and applications. In addition to the XML technologies that InfoPath supports, InfoPath makes use of special processing instructions (processing instructions: Information stored in the prologue of an XML document. This information is passed through the XML parser to any application that uses the XML document.) and namespaces (namespace: A mechanism that uniquely qualifies element names and relationships to avoid name collisions on elements that have the same name but are coming from multiple sources.), and has a number of methods for accessing the DOM through the InfoPath object model.

Although it is not necessary to understand all of the details of these XML technologies, the following table will help you understand how these technologies are used in InfoPath.

Name	Description
XML	XML is the output format that is produced by an InfoPath form. XML is also used to contain the sample data that is displayed in the fields of a form before a user fills it out. InfoPath uses the XML version 1.0 standard.
XSLT	XSLT is the format of the view files that are produced when a form template is designed. InfoPath does not support the use of XSL Formatting Objects (XSL-FO) for the presentation of XML data, nor does it support the importing of arbitrary .xsl files. InfoPath uses the XSLT version 1.0 standard.
XML Schema	XML Schemas are used as the primary means of data validation (data validation: The process of testing the accuracy of data; a set of rules you can apply to a control to specify the type and range of data that users can enter.) in a form, and they provide the underlying structure of the XML document that is produced by the form template. In addition, an XML Schema is used to define the structure of the form definition (.xsf) file (form definition file: An XML file with an .xsf extension that contains information about all other files and components used within a form, including user interface customizations, XML Schemas, views, business logic, events, and deployment settings.) that is generated by InfoPath when a form template is designed. InfoPath does not support schemas that comply with the XML-Data Reduced (XDR) or Document Type Definition (DTD) specifications. InfoPath uses the XML Schema version 1.0 standard.
XHTML	XHTML is well-formed HTML and is primarily used when developing rich text areas. InfoPath uses the XHTML version 1.0 standard.
XPath	XPath expressions are used when binding (bind: To connect a control to a field or group in the data source so that data entered into the control is saved. When a control is unbound, it is not connected to a field or group, and so data entered into the control will not be saved.) controls to fields and groups in a form template's data source (data source: The collection of fields and groups that define and store the data for an InfoPath form. Controls in the form are bound to the fields and groups in the data source.). XPath expressions are also used for data validation and conditional formatting (conditional formatting: The process of changing the appearance of a control, including its visibility and read-write state, based on values entered into the form.) expressions. InfoPath uses the XPath version 1.0 standard.
DOM	The DOM is used to programmatically access the contents of the source XML document that a form template produces. It is also used to provide read-only access to the contents of the .xsf file. InfoPath uses the DOM version 1.0 standard.
XML Signature	XML Signatures are used to digitally sign InfoPath forms. If enabled, each InfoPath form can contain one or more digital signatures. InfoPath supports digital signing of portions of a form, as well as the form as a whole.
XML processor	The XML processor is used to load the source XML of a document into the dynamic memory of the computer, validate it using the XML Schema, and produce the view of the document by using XSLT. The XML processor supported by InfoPath is Microsoft XML Core Services (MSXML) version 5.0. Earlier versions of this processor are not supported.