![23
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 see
the text as is,
even though
it includes tags](https://image.slidesharecdn.com/xml2-150305003325-conversion-gate01/85/Xml-2-23-320.jpg)
Xml (2)
- 2. 2 Introduction and Motivation Dr. Praveen Madiraju Modified from Dr.Sagiv’s slides
- 3. 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. 4 An Address Book as an XML document <addresses> <person> <name> Donald Duck</name> <tel> 414-222-1234 </tel> <email> donald@yahoo.com </email> </person> <person> <name> Miki Mouse</name> <tel> 123-456-7890 </tel> <email>miki@yahoo.com</email> </person> </addresses>
- 5. 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. 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)
- 7. 7 XML is the Standard for Data 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. 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. 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. 10 XML can Describe the 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. 11 XML Syntax W3Schools Resources on XML Syntax
- 12. 12 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 <i> ... <b> ... </i> ...</b> in HTML)
- 13. 13 A Useful Abbreviation Abbreviating elements with empty contents: • <br/> for <br></br> • <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
- 14. 14 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., Œ for the Hebrew letter Mem
- 15. 15 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> lisa@cs.huji.ac.il </email> </person>
- 16. 16 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>
- 17. 17 XML Structure (cont’d) <addresses> <person> <name> Donald Duck</name> <tel> 04-828-1345 </tel> <email> donald@cs.technion.ac.il </email> </person> <person> <name> Miki Mouse</name> <tel> 03-426-1142 </tel> <email>miki@yahoo.com</email> </person> </addresses>
- 18. 18 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> bart@tau.ac.il </email> </person> element element, a sub-element of not an element
- 19. 19 An XML Document is a Tree person name emailtel tel Bart Simpson 02 – 444 7777 051 – 011 022 bart@tau.ac.il Leaves are either empty or contain PCDATA
- 20. 20 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>
- 21. 21 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
- 22. 22 Processing Instructions <?xml version="1.0"?> <?xml-stylesheet href="doc.xsl" type="text/xsl"?> <!DOCTYPE doc SYSTEM "doc.dtd"> <doc>Hello, world!<!-- Comment 1 --></doc> <?pi-without-data?> <!-- Comment 2 --> <!-- Comment 3 -->
- 23. 23 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 see the text as is, even though it includes tags
- 24. 24 A Complete XML Document http://www.mscs.mu.edu/~praveen/Teaching/fa
- 25. 25 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
- 26. 26 Representing relational databases A relational database for school: student: course: enroll: cno title credit 331 DB 3.0 350 Web 3.0 … … … id name gpa 001 Joe 3.0 002 Mary 4.0 … … … id cno 001 331 001 350 002 331 … …
- 27. 27 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>
- 28. 28 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>
Editor's Notes
- #14: &lt;number&gt;