Intro. to XML & XML DB

Intro. to XML & XML DB

Bun YueProfessor, CS/CISUHCL

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), http://www.w3.org/XML/.

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: <p>, <body>, <li>, etc, but not <chapter> or <bun>

HTML can be defined using XML: XHTML.

HTML Examplesmemo.xml:

<?xml version="1.0"?><memo priority="very high"><from>Bun Yue</from><to>Everybody</to><body>Hello, welcome!</body></memo>

HTML vs XML

XML HTML

Meta-language for defining Markup lang.

Markup language

Data only Data and display info

Application structures; no intrinsic display info.

Display information

All applications Mostly Web Client Application

Issues with HTML No meaning on document structures. Hard to support a Semantic Web Example: human vs machine in:<h2>Bun Yue</h2><h2>Introduction to XML</h2>vs<instructor>Bun Yue</instructor><course>Introduction to XML</course> 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

Intro. to XML & XML DB

Documents