+ 1 xml extensible markup language. + 2 xml lecture adapted from the work of dr. praveen madiraju of...

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1

XML

eXtensible Markup Language

2+XML Lecture

Adapted from the work of Dr. Praveen Madiraju of Marquette University

3+XML vs. HTML

HTML is a HyperText Markup language Designed for a specific application, namely, presenting and

linking hypertext documents

XML describes structure and content (“semantics”) The presentation is defined separately from the structure

and the content

4+ An Address Book asan XML document<addresses>

<person><name> Donald Duck</name><tel> 414-222-1234 </tel><email> [email protected] </email>

</person><person>

<name> Miki Mouse</name><tel> 123-456-7890 </tel><email>[email protected]</email>

</person></addresses>

5+Main Features of XML

No fixed set of tags New tags can be added for new applications

An agreed upon set of tags can be used in many applications Namespaces facilitate uniform and coherent descriptions of

data For example, a namespace for address books determines

whether to use <tel> or <phone>

6+Main Features of XML (cont’d) XML has the concept of a schema

DTD and the more expressive XML Schema

XML is a data model Similar to the semistructured data model

XML supports internationalization (Unicode) and platform independence (an XML file is just a character file)

http://www.unicode.org/

7+XML is the Standard forData Exchange Web services (e.g., ecommerce) require exchanging

data between various applications that run on different platforms

XML (augmented with namespaces) is the preferred syntax for data exchange on the Web

8+ XML is not Alone

XML Schemas strengthen the data-modeling capabilities of XML (in comparison to XML with only DTDs)

XPath is a language for accessing parts of XML documents

XLink and XPointer support cross-references

XSLT is a language for transforming XML documents into other XML documents (including XHTML, for displaying XML files) Limited styling of XML can be done with CSS alone

XQuery is a lanaguage for querying XML documents

9+The Two Facets of XML

Some XML files are just text documents with tags that denote their structure and include some metadata (e.g., an attribute that gives the name of the person who did the proofreading) See an example on the next slide XML is a subset of SGML (Standard

Generalized Markup Language)

Other XML documents are similar to database files (e.g., an address book)

10+XML can Describethe Structure of a Document <book year="1994">

<title>TCP/IP Illustrated</title><author>

<last>Stevens</last><first>W.</first>

</author><publisher>Addison-Wesley</publisher><price>65.95</price>

</book>

11+ The Structure of XML

XML consists of tags and text

Tags come in pairs <date> ... </date>

They must be properly nested good

<date> ... <day> ... </day> ... </date> bad

<date> ... <day> ... </date>... </day>

(You can’t do ... ... ... in HTML)

12+ A Useful Abbreviation

Abbreviating elements with empty contents:

 for 

<hr width=“10”/> for <hr width=“10”></hr>

For example:

<family>

<person id = “lisa”>

<name> Lisa Simpson </name>

<mother idref = “marge”/>

<father idref = “homer”/>

</person>

...

</family>

Note that a tag may have a set of attributes, each consisting of a name and a value

13+ XML Text

XML has only one “basic” type – text

It is bounded by tags, e.g.,

<title> The Big Sleep </title>

<year> 1935 </ year> – 1935 is still text

XML text is called PCDATA (for parsed character data)

It uses a 16-bit encoding, e.g., \&\#x0152 for the Hebrew letter Mem

14+XML Structure

Nesting tags can be used to express various structures, e.g., a tuple (record):

<person><name> Lisa Simpson</name><tel> 02-828-1234 </tel><tel> 054-470-777 </tel><email> [email protected] </email>

</person>

15+XML Structure (cont’d)

We can represent a list by using the same tag repeatedly:

<addresses><person> … </person><person> … </person><person> … </person><person> … </person>…

</addresses>

16+XML Structure (cont’d)

<addresses><person>

<name> Donald Duck</name><tel> 04-828-1345 </tel><email> [email protected] </email>

</person><person>

<name> Miki Mouse</name><tel> 03-426-1142 </tel><email>[email protected]</email>

</person></addresses>

17+ Terminology

The segment of an XML document between an opening and a corresponding closing tag is called an element

<person> <name> Bart Simpson </name>

<tel> 02 – 444 7777 </tel> <tel> 051 – 011 022 </tel>

<email> [email protected] </email> </person>

element

element, a sub-element of

not an element

18+An XML Document is a Tree

person

name emailtel tel

Bart Simpson

02 – 444 7777

051 – 011 022

[email protected]

Leaves are either empty or contain PCDATA

19+ Mixed Content

An element may contain a mixture of sub-elements and PCDATA

<airline>

<name> British Airways </name>

<motto>

World’s <dubious> favorite</dubious>

airline

</motto>

</airline>

20+The Header Tag

<?xml version="1.0" standalone="yes/no" encoding="UTF-8"?> Standalone=“no” means that there is an external DTD

You can leave out the encoding attribute and the processor will use the UTF-8 default

21+ Processing Instructions

<?xml version="1.0"?>

<?xml-stylesheet href="doc.xsl" type="text/xsl"?>

<!DOCTYPE doc SYSTEM "doc.dtd">

<doc>Hello, world!</doc>

<?pi-without-data?>

22+ Using CDATA

<HEAD1> Entering a Kennel Club Member

</HEAD1>

<DESCRIPTION>Enter the member by the name on his or her papers. Use the NAME tag. The NAME tag has two attributes. Common (all in lowercase, please!) is the dog's call name. Breed (also in all lowercase) is the dog's breed. Please see the breed reference guide for acceptable breeds. Your entry should look something like this:

</DESCRIPTION>

<EXAMPLE><![CDATA[<NAME common="freddy" breed"=springer-spaniel">Sir Fredrick of Ledyard's End</NAME>]]>

</EXAMPLE>

We want to seethe text as is,even though

it includes tags

23+ A Complete XML Document

http://www.personal.psu.edu/nna102/IST210/sample.xml

(linked from the schedule page)



24+ Well-Formed XML Documents

An XML document (with or without a DTD) is well-formed if Tags are syntactically correct

Every tag has an end tag

Tags are properly nested

There is a root tag

A start tag does not have two occurrences of the same attribute

An XML document must be well formed

25+Representing relational databases

A relational database for school:student: course:

enroll:

cno title credit

331 DB 3.0350 Web 3.0… … …

id name gpa

001 J oe 3.0002 Mary 4.0… … …

id cno

001 331001 350002 331… …

26+XML representation

<school>

<student id=“001”>

<name> Joe </name> <gpa> 3.0 </gpa>

</student>

<student id=“002”>

<name> Mary </name> <gpa> 4.0 </gpa>

</student>

<course cno=“331”>

<title> DB </title> <credit> 3.0 </credit>

</course>

<course cno=“350”>

<title> Web </title> <credit> 3.0 </credit>

</course>

27+XML representation

<enroll>

<id> 001 </id> <cno> 331 </cno>

</enroll>

<enroll>

<id> 001 </id> <cno> 350 </cno>

</enroll>

<enroll>

<id> 002 </id> <cno> 331 </cno>

</enroll>

</school>

+XML Introduction

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

processing for expressing database views. Document processing needs database

processing for storing and manipulating data.

As Internet usage increases, organizations want to make their Web pages more functional by displaying and updating data from organizational databases.KROENKE and AUER - DATABASE CONCEPTS (6th Edition)

Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

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+XML

XML, or Extensible Markup Language, was developed in the early 1990s. XML is a subset of SGML or Standard Generalized

Markup Language.

Today XML is a hybrid of document processing and database processing. It provides a standardized yet customizable way to describe

the content of documents. XML documents can automatically be generated from

database data and vice versa.

SOAP is an XML-based standard protocol for sending messages of any type, using any protocol over the Internet.

KROENKE and AUER - DATABASE CONCEPTS (6th Edition) Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

7-29

+XML (Cont’d)

XML is used for describing, representing ,and materializing database views.

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

structure, content and materialization. It is standardized but allows for extension by

developers. XML tags accurately represent the semantics of their

data.


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+SQL for XML Processing


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Figure 7-28: An SQL FOR XML Query

+Results ofSQL for XML Processing


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Figure 7-29: Results of the SQL FOR XML Query

+XLM Web Services

XML Web Services allow application functionality on one Web server to be shared and incorporated into Web applications on other Web servers.


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