Applying XML

1
Applying XML

• Mark A. Cohen
• Instructor of Computer Information Science
• Lock Haven University
• February 22, 2005

2
Computers Need Structure

• Johnny Smith first entered this world on July 4th
  1969. He resides in Philadelphia, PA and is
  employed full-time with the National Parks
  Service.
• If you feed this text to a computer, can it
  figure out that we are talking about a person
  named Johnny Smith. Can it tell where Johnny
  lives, works, or when he was born?

3
Proprietary Data Formats

• To solve this problem software developers have
  created custom formats that have structure, and
  are therefore easier for computers to read
• Each application often has its own custom format,
  and the format is often in binary form
• Custom formats require custom parsers
• Binary formats are hard for people to read
• Binary formats can be platform specific
• For programs to communicate, they need to be able
  to understand multiple formats and have multiple
  parsers

4
XML to the Rescue

• XML adds structure text (by marking it up) so
  it can be read by a computer.
• ltpersongtltfirstgtJohnnylt/firstgt ltlastgtSmithlt/lastgt
  first entered this world on ltdobgtJuly 4th
  1969lt/dobgt. He resides in ltlivesgtPhiladelphia,
  PAlt/livesgt and is employed full-time with the
  ltemployer typefull-timegtNational Parks
  Servicelt/employergtlt/persongt.

5
Advantages of XML

• You only need one parser
• Structure makes it easier to for computers to
  read and text-based so it is easy to read by
  humans
• Text-based data is portable across platforms
• Applications can talk more easily and share data
  if they speak the same language

6
The Parsing is Free!

• Document doc db.parse(urlString)
• Element elem doc.getDocumentElement()
• NodeList nl elem.getElementsByTagName(first")
• for (int n0 nltnl.getLength() n)
• Element first (Element)nl.item(n)
• System.out.pritnln
• (first.getFirstChild())

7
Many Applications

• The ability to parse data without having to write
  a parser is a wonderful thing. Just how
  wonderful can be demonstrated by looking at the
  many ways XML is being applied.
• HTML?
• New Programming Languages
• Databases
• Simple Remote Procedure Calls
• Configuration Files
• Transforming Data into Many Formats

8
Is HTML XML?

• Is this valid HTML?
• ltulgt
• ltligtltpgtThe answer is yes!
• lt/ulgt
• Is it valid XML? The answer is no because it is
  not well-formed Not every tag has a closing tag.
  For this reason, parsing HTML is much harder
  than parsing XML.
• XHTML is HTML that conforms to the rules of
  well-formed XML.

9
XML-Based Programming Languages

• The ability to get a parser for free makes it
  really easy to create new programming languages.
• The syntax checking is free
• Language designers can focus on implementing the
  language
• Since XML is a standard, XML based tools will
  work with any XML-based programming language

10
Scalable Vector Graphics (SVG)

• ltsvggt
• ltrect x"1" y"1"
• width"1198" height"398"
• fill"none"
• stroke"blue"
• stroke-width"2"gt
• lt/rectgt
• ltrect x"400" y"100"
• width"400" height"200"
• fill"yellow" strokeblue"
• stroke-width"10" /gt
• lt/rectgt
• lt/svggt

You can viewing an SVG program in a web browser
by installing a free SVG viewer from
http//www.adobe.com/svg/viewer/install/
11
Jelly

• ltjjelly xmlnsj"jellycore"gt
• ltjchoosegt
• ltjwhen test"user.locale'de_AT'"gt
• Servus user.name
• lt/jwhengt
• ltjotherwisegt
• Hello user.name
• lt/jotherwisegt
• lt/jchoosegt
• lt/jjellygt

12
XML Database Queries

• ltxsqlquery xmlnsxsql"urnoracle-xsql"gtSELECT
  name, ageFROM peopleWHERE name Tom
• lt/xsqlquerygt
• ltROWSETgt  ltROW num"1"gt    ltNAMEgtTomlt/NAMEgt    
  ltagegt21lt/agegt  lt/ROWgt
• lt/ROWSETgt

13
Remote Procedure Calls

• ltmethodCallgt
• ltmethodNamegtgetPricelt/methodNamegt
• ltparamsgt
• ltparamgt
• ltvaluegt
• ltsymbolgtIBMlt/symbolgt
• lt/valuegt
• lt/paramgt
• lt/paramsgt
• lt/methodCallgt

14
Configuration Files

• ltoutlookgt
• ltprofile nameMarkgt
• ltsendFormatgthtmllt/sendFormatgt
• ltrecFormatgtplain-textlt/recFormatgt
• ltfontgtCourier New 12ptlt/fontgt
• ltdeleteOnClosegttruelt/deleteOnClosegt
• ltmailfoldergtc\mail\marklt/mailfoldergt
• lt/profilegt
• ltprofile nameLisagt
• ltsendFormatgtrtflt/sendFormatgt
• ltrecFormatgtplain-textlt/recFormatgt
• ltfontgtArial 10ptlt/fontgt
• ltdeleteOnClosegttruelt/deleteOnClosegt
• ltmailfoldergtc\mail\lisalt/mailfoldergt
• lt/profilegt
• lt/outlookgt

15
Easy Parsing Means Simple Transformations
Cohen, Mark Phone [phone] email
mark_at_b.c
ltcontactgt ltfirstgtMarklt/firstgt
ltlastgtCohenlt/lastgt ltphonegt111-2222lt/phonegt
ltemailgtmark_at_b.clt/emailgt lt/contactgt
Parse Transform
Mark Cohen can be reached at 111-2222, or via
email at mark_at_b.c.
ltpersongt ltnamegtMark Cohenlt/namegt lt/persongt
16
XSLT

• Since transforming XML is so useful, a special
  XML-based programming language was created to
  simplify the task
• ltxsltemplate matchfirstgt
• For a good time call ltxslvalue-of
  select./gt!
• lt/xsltemplategt
• For a good time call Johnny!