IT420: Database Management and Organization

XML21 April 2006

Adina Crăiniceanuwww.cs.usna.edu/~adina

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Overview

From HTML to XML DTDs Transforming XML: XSLT

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Introduction

Database processing and document processing need each other Database processing needs document processing for

transmitting/ expressing database views Document processing needs database processing for

storing and manipulating data Internet expansion made the need obvious

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XML

XML: Extensible Markup Language, developed in early 1990s

Hybrid of document processing and database processing It provides a standardized yet customizable way to

describe the content of documents A recommendation from the W3C

XML = data + structure XML generated by applications XML consumed by applications Easy access: across platforms, organizations

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XML

What is this? What does it mean?

<h2>Madison</h2>

HTML: How to display information on a browser.

HTML: no “semantic” information, i.e. no meaning ascribed to tags

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XML: Semantic information

<presidents> <name>Madison</name>

<US_cities> <Wisconsin> <name>Madison</name>

<US_Colleges> <name>Madison, U of Wisc</name> <name> Madison, James (JMU)</name>

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XML vs. HTML

XML is better than HTML because It provides a clear separation between document

structure content materialization

It is standardized but allows for extension by developers XML tags represent the semantics of their data

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Why is XML important with regard to databases? XML provides a standardized way to

describe, validate, and materialize any database view. Share information between disparate systems Materialize data anyway you want

Display data on web Display data on sales-person computer Display data on mobile device

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How does XML work?

Three Primary Components to XML Data has a structure

Document Type Declarations (DTDs) XML Schemas can be used to describe the

content of XML documents

Data has content XML document

Data has materializations Extensible Style Language: Transformations

(XSLT)

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If we want to share information is structure important? Structure provides meaning

10111011000101110110100101010101101010110110101….

What is the meaning of this bit stream??

The bit stream has meaning if we assign structure

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Example: XML DTD & Document

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XML DTD

XML document consists of two sections: Document Type Declaration (DTD)

The DTD begins with DOCTYPE <document_type_name>

Document data

XML documents could be Type-valid if the document conforms to its DTD Well-formed and not be type-valid, because

It violates the structure of its DTD It has no DTD

DTD may be stored externally so many documents can be validated against the same DTD

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Create XML Documents from Relational DB Data Most RDBMS can output data in XML

format MySQL: mysql –u root --xml For SQL Server:

SELECT . . . FOR XML RAW | AUTO, ELEMENTS | EXPLICIT

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Lab exercise

Restore some database in MySQL Open MySQL command line using

mysql –u root --xml

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XSLT

XSLT, or the Extensible Style Language may be used to materialize (transform) XML documents using XSL document From XML documents into HTML or into XML in

another format

XSLT is a declarative transformation language XSLT uses stylesheets to indicate how to

transform the elements of the XML document into another format

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Example: External DTD<?xml version="1.0" encoding="UTF-8"?><!ELEMENT customerlist (customer+)><!ELEMENT customer (name, address)><!ELEMENT name (firstname, lastname)><!ELEMENT firstname (#PCDATA)><!ELEMENT lastname (#PCDATA)><!ELEMENT address (street+, city, state, zip)><!ELEMENT street (#PCDATA)><!ELEMENT city (#PCDATA)><!ELEMENT state (#PCDATA)><!ELEMENT zip (#PCDATA)>

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Example: XML Document<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE customerlist SYSTEM "http://localhost/Support-Files-Chap-13-XML/CustomerList.dtd"> <?xml-stylesheet type="text/xsl" href="http://localhost/Support-Files-Chap-13-XML/CustomerList-StyleSheet.xsl"?><customerlist>

<customer><name>

<firstname>Michelle</firstname><lastname>Correlli</lastname>

</name><address>

<street>1824 East 7th Avenue</street><street>Suite 700</street><city>Memphis</city><state>TN</state><zip>32123-7788</zip>

</address></customer><customer>

<name><firstname>Lynda</firstname><lastname>Jaynes</lastname>

</name><address>

<street>2 Elm Street</street><city>New York City</city><state>NY</state><zip>02123-7445</zip>

</address></customer>

</customerlist>

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XSL Stylesheet for CustomerList

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Example: XML Browser

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Show XSL document example

CustomerList.xml

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XML Review

STRUCTURE: DTD or XML Schema CONTENT: XML document MATERIALIZATIONS: XSL document

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Sharing Data: Transparency

XMLdata

XSLTrans

ValidateDTD

DatabaseRaw data

ValidateDTD

XSLTrans

XMLdata

DatabaseRaw data

Business A Business B

Agreed uponstructure

SHARE

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Example XML Industry Standards Accounting

Extensible Financial Reporting Markup Language (XFRML) Architecture and Construction

Architecture, Engineering, and Construction XML (aecXML) Automotive

Automotive Industry Action Group (AIAG) XML for the Automotive Industry (SAE J2008)

Banking Banking Industry Technology Secretariat (BITS) Bank Internet Payment System (BIPS)

Electronic Data Interchange Data Interchange Standards Association (DISA) XML/EDI Group

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What About XML Queries?

Xpath A single-document language for “path

expressions” Not unlike regular expressions on tags E.g. /Contract/*/UnitPrice,

/Contract//UnitPrice, etc. XSLT

XPath plus a language for formatting output XQuery

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Conclusions

XML: The new universal data exchange format

Unlike HTML, XML = data + semantics STRUCTURE: DTD or XML Schema CONTENT: XML document MATERIALIZATIONS: XSL document

More flexible than relational model More difficult to query – research