Intro. to XML & XML DB Bun Yue Professor, CS/CIS UHCL

Intro. To XML  XML stands for eXtensible Markup Language.  XML is a system for defining, validating, and sharing documents.  Main standard organization: World Wide Web Consortium (W3C),

Background: SGML  XML is a simplified version of the Standard Generalized Markup Language (SGML).  Both XML and SGML may be considered as meta-languages for creating markup languages.  A valid XML document is also a SGML document.

Background: HTML  XML uses: Elements for document structures Attributes to describe their properties  Unlike HTML, authors use XML to define and share vocabularies.  As a comparison, HTML has a fixed set of elements:,,, etc, but not or  HTML can be defined using XML: XHTML.

HTML Examples memo.xml: Bun Yue Everybody Hello, welcome!

HTML vs XML XMLHTML Meta-language for defining Markup lang. Markup language Data onlyData and display info Application structures; no intrinsic display info. Display information All applicationsMostly Web Client Application

Issues with HTML  No meaning on document structures.  Hard to support a Semantic Web  Example: human vs machine in: Bun Yue Introduction to XML vs Bun Yue Introduction to XML  HTML Scalping is hard!

Issues in HTML  A traditional HTML files put the following three major components in one document: Data contents Presentation design Programming logic  However, it may be desirable to have three different development teams to create the three components.  Results: difficult to create and maintain.

XML in Web Applications  XML assists in the separation of data from presentation.  Can database be used for the same purpose? Discuss!

Advantages of XML  Strict syntax with unambiguous structures for simpler and more meaningful processing.  Better modeling of application domain.  Validation for early error checking.  Extensible to fit requirements of different domains.  Human readable.  Abundance of tools.

Some Disadvantages of XML  Verbose  Text-based  Tree-based structures  …  This is not a complete list. We will revisit this issue later.

Core XML Standards  XML Specification: XML syntax.  XML Namespace: defining address spaces to avoid naming conflicts.  DTD (Document Type Definition): specifying grammars of XML vocabularies.  XML Schema: a newer and more powerful way to define XML grammars that is itself in XML format.

Core XML Standards  XLink: linking between XML documents.  XPointer: referring to parts of an XML document.  XPath: searching an XML document.  XQuery: XML query language in the line of SQL.

Core XML Standards  CSS (Cascading Stylesheet): a style sheet standard for viewing XML and HTML.  XSL (eXtensible Stylesheet Language): for displaying and transforming XML documents: XSLT: the XSL part for XML transformation. FO: formatting object, the display part of XSL.

Core XML Standards  DOM (Document Object Model): W3C standard for object and interface collections for manipulating XML documents (and HTML, etc).

Tools and Technology  XML Editors:  XML Parsers: DOM: create a document object (tree based) SAX: event driven  Querying: XPath XSLT XQuery

Tools and Technology  XML Server: serve XML Data source management Transformation Consumption support, e.g.  RESTful (Representational state transfer)  XQJ API (XQuery API for Java) Content and subscription management  XML DB: storage of collection of XML documents.

XML DB  Persistence and efficient access of collections of XML documents.  XML Enabled DB: DB provides features for production and consumption of XML. Underlying storage may not be in XML format: e.g. relations.

Native XML DB  XML document as the basic data model.  XML document as a fundamental storage unit.  Standalone or not. E.g. Oracle 11g XML DB native but part of 11g.

Querying  XQuery support

Questions