XML Documentation

Extensible Markup Language (XML) provides a significant advance in how data is described and exchanged by Web-based applications using a simple, flexible standards-based format. Hypertext markup language (HTML) enables universal methods for viewing data; XML provides universal methods for working directly with data.

• XML, DTD, and Schemas
• XML Glossary
• Data Types

XML, DTD, and Schemas

XML is the universal language for data on the Web. It gives developers the power to deliver structured data from a wide variety of applications to the desktop for local computation and presentation. XML allows the creation of unique data formats for specific applications. It is also an ideal format for server-to-server transfer of structured data.

The document type definition (DTD) defines the valid syntax of a class of XML documents. That is, it lists a number of element names, which elements can appear in combination with which other ones, what attributes are available for each element type, etc. A DTD uses a different syntax from that used by XML documents.

Schemas combine concepts from DTDs, relational databases, and object-oriented design. Schemas, outlined in the XML-Data proposal submitted to the W3C, can describe the structure of XML documents, databases, direct-label graphs, and other, similar organizations of data. Schemas supply additional semantic information to documents that are not available in DTDs and contain new facilities such as data types, inheritance, and extensibility. In addition, schemas use the same syntax as XML documents, rather than the unique syntax used by DTDs. Schema components are reusable through the facility of XML namespaces.

See www.microsoft.com/xml/  for more information.

Notes:

• Support for data types in PC-SPAN 4 may be added in the future. It will require the usage of schemas. No changes in Span XML files containing business data will be needed to take advantage of data typing.  The XML-Data data typing mechanism has already been wired into the IE5 code -- string, number, int, float, fixed, boolean, data, time, uuid, uir, and other types are supported.

• Support for default element values may also be added in the future.  Again, no changes in Span XML files will be needed.

XML Glossary

Element - fundamental logical unit of an XML document, used to store the system's data.

• The commas (,) between elements indicates that they must occur in succession.
• The plus (+) after an element indicates that it may be repeated more than once but must occur at least once.
• The question mark (?) after an element makes it optional, but only one may appear.
• An element with no punctuation must occur exactly once.
• The vertical bar (|) indicates an "or" relationship.
• The asterisk (*) indicates that the content is optional (may occur zero or more times).
• EMPTY indicates that an element has no textual content. Empty elements may contain attributes only.
• Parsed character data (#PCDATA) is text that will be examined by the parser for entities and markup.

Attribute - source of additional information about an element, used for meta-data (e.g. datatypes).

• Character data (CDATA) type attributes may contain only character data.
• The value of an enumerated type attribute must match one of the values listed. Values must appear in parentheses and separated by OR (|) symbols.
• Attribute may be required (#REQUIRED), optional (#IMPLIED), or have a default value in quotes.
• All attribute values must be quoted.

Entity - a reference to other data that often acts as an abbreviation or a shortcut.

Data Types

The following table lists the data types supported by the MSXML parser in Microsoft® Internet Explorer 5.0.