XML is a set of rules for building markup languages. It is not just glorified HTML or only for the i

1
Characterizing XML

• XML is a set of rules for building markup
  languages. It is not just glorified HTML or only
  for the internet.
• XML is a family of technologies that can do
  everything from formatting documents to filtering
  data.
• XML is a philosophy for information handling that
  seeks to maximize usefulness and flexibility of
  data by refining it to its purest and most
  structured form.

2
XML A Family of Technologies

• XML to Formatted Presentation (HTML, PDF, user
  created format, etc.)
• Combining what we wanted to previously keep
  separate markup and style.
• Why?
• Author can concentrate on meaning
• Designer can concentrate on appearance
• More options for presentation

3
XML Application DocBookhttp//www.oasis-open.or
g/docbook/

• DocBook a markup language (DTD) for technical
  documentation of computer hardware and software.
• Consists of several hundred elements.
• Elements include ltbibliographygt, ltkeywordgt,
  ltitemized listgt, ltfiguregt, lttablegt

4
DocBook vs. Word Processor

• lttablegt prevents a user from creating an image to
  hold data which cannot be searched.
• Papers would be easier to write! Each publisher
  could still use their own display format
  (different CSSs or XML Schemas) and users only
  need to worry about content.
• Searching for scientific papers on a topic would
  be easier and faster.
• Search methods not possible now could be done.
• Can search by element instead of just by keyword.
• Can have more complex querying

5
XML Applications and Tools

• XML Application a markup language derived from
  XML rules (e.g. DocBook)
• XML Software applications set of components,
  each performing a crucial step on an assembly
  line (XML processors)
• XML Tools commercially available programs that
  help a user work with XML

6
XML Processors

• Set of components, each performing a crucial step
  on an
• assembly line
• 1. Parser translate XML markup and data into
  tokens
• 2. Event Switcher routes tokens to event
  handling routines (CSS)
• 3. Tree Representation a tree structure is
  built if more complicated processing of an XML
  document is needed
• a. Simple hierarchy of nodes
• b. Object Model each node represented as an
  object
• 4. Tree Processor
• -traverses a tree so operations can be done on
  the tree model
• -validity checker to a full transformation
  engine

7
XML Software Applications
http//www.garshol.priv.no/download/xmltools/cat_i
x.html

• Editing and Composition
• Electronic Delivery
• Control Information and Development
• Conversion
• Document Storage and Management
• Parsers and Engines

8
XML Software Applications

• XML has a lot of different parts and at first
  seems to be very complex.
• Each part by itself is simple.
• There is no need to be an expert in all of XML to
  be able to use it productively.

9
XML Software Applications

• Editing and composition (Tools for interactive
  creation, modification and composition of XML
  documents.)
• XML Editors
• Text emacs, vi
• Graphical HTML-Kit, etc.
• Electronic delivery (Tools for electronic
  delivery and display of XML documents)
• XML Browsers
• Amaya (W3C) - HTML/XHTML browser/editor w/CSS and
  XLinks support
• InDelv XML Client XSLT style sheets for
  display, supports XPath and XPointer
• IE5.5 displays XML with CSS or XSLT
• Mozilla(Netscape) displays XML with CSS
• IBM Alphaworks DTD aware

10
XML Software Applications

• Control information and development (Tools for
  creating, modifying and documenting DTDs, XSL
  style sheets etc.)
• CSS Editors/DTD Editors (similar to XML editors
  some overlap)
• DTD Documenters
• LiveDTD - parses XML DTDs and generates
  documentation HTML files from the DTDs with
  cross-links to element and parameter entity
  definitions.
• DTD Generators
• Data Descriptors by Example -automatically
  generate an XML DTD or schema from a set of
  document instances.
• Rhythmyx XSpLit - claims to be able to
  automatically generate an XML DTD and an XSLT
  style sheet from a sample HTML document. The XSLT
  style sheet can then be combined with XML
  documents that conform to the XML DTD to produce
  HTML pages with the same design as the original,
  but with new content.
• SAXON includes a small application that can
  generate DTDs from sample input files
• DTD Parsers
• Schema Converters
• DTD2RELAX - converts a DTD into a RELAX schema
  module.

11
XML Software Applications

• Control information and development (cond)
• XSL Checkers
• XSL Lint checks XSLT style sheets for mistakes
• XSL Trace debugger for XSLT style sheets
• XSL Converters
• XSLT is a subset of the more general XSL, these
  programs convert from XSL to XSLT
• XSLT Editors
• XSLT Generators
• WH2FO - reads HTML files produced by Microsoft
  Word and converts it into an XML document, with
  two XSLT style sheets one for conversion back to
  HTML and one for conversion to XSL-FO (Extensible
  Style Sheet Language for Formatting Objects
  another subset of XSL)
• Rhythmyx XSpLit

12
XML Software Applications

• Conversion (Tools for scripted creation and
  modification of XML documents.)
• General N-converters convert from non-XML
  (usually word processing document) to XML
• General S-converters process XML documents
  (Transformation)
• Publishing Converters
• TeXML - an XML DTD and a Java application called
  TeXMLatte. TeXMLatte takes TeXML documents and
  converts them to TeX. This can be used with, for
  example, an XSL XML-to-TeXML conversion to
  produce TeX output from XML source documents.
  TeXML can also convert to plain text.

13
XML Software Applications

• Document Storage and Management (Tools for
  supporting document management, such as document
  databases and search engines.)
• XML document database systems (systems for
  persistently storing XML documents and providing
  access to their structure and individual parts.)
• Lore - a DBMS built specifically for the XML data
  model, complete with query language, query
  optimizer, indexing, multi-user support and
  recovery.
• XML-DBMS - a Java library that can be used to
  move data from XML to a relational database and
  also back again.
• XML search engines
• Xset - an XML search engine oriented towards
  performance. It keeps its working set in memory
  (using paging to support large documents) and can
  be accessed through RMI. The query language is
  very simple.
• sgrep - a general tool for searching and indexing
  text that supports XML (and SGML). It also has
  its own very powerful query language.

14
XML Software Applications

• Parsers and Engines (XML parsers, parsing
  toolkits, HyTime engines and DSSSL engines
• DOM implementations set of Java interfaces
  declaring methods that the developer should
  create
• DSSSL engines for formatting SGML docs
• RDF parsers
• SGML/XML parsers
• XLink/XPointer engines
• Jaxon - parse XPath expressions, and evaluate
  them against XML tree representation
• XML Middleware - General software packages for
  making XML-aware applications of some form.
• XML Parsers translate XML markup data into
  tokens to be processed
• XML Validators - Software for validating XML
  documents by other means than DTDs.
• XSL engines - Engines that support the XSL
  formatting objects specification.
• XSLT engines - Engines that support the XSL
  Transformations specification.

15
DTD vs. XML Schema

• DTD drawbacks
• Enforcing an elements range of occurrences
• A fruit_basket can have between 5 and 7 banana
  elements
• lt!ELEMENT fruit_basket (    (banana, banana,
  banana, banana, banana)     (banana, banana,
  banana, banana, banana, banana)     (banana,
  banana, banana, banana, banana, banana, banana)gt
• Enforcing a numbering scheme on child elements
• A fruit_basket can have 3 bananas each numbered 1
  through 3
• Cannot be done with a DTD
• lt!ELEMENT fruit_basket (banana)gtlt!ELEMENT
  banana EMPTYgtlt!ATTLIST banana banana_number (1
  2 3) "1" gt

16
DTD vs. XML Schema

• Enforcing an elements range of occurrences
• Use XML Schema
• ltxsdcomplexType name"fruit_basket"gt  
  ltxsdelement name"banana" minOccurs"9"
  maxOccurs"11"/gtlt/xsdcomplexTypegt

17
DTD vs. XML Schema

• Enforcing a numbering scheme on child elements
  XSLT style sheet
• ltxslstyle sheet xmlnsxsl"http//www.w3.org/1999
  /XSL/Transform"   xmlns"http//www.w3.org/1999/x
  html" version"1.0"gt   lt!-- Process
  fruit_basket element(s) --gt   ltxsltemplate
  match"fruit_basket"gt   lthtmlgt     
  ltbodygt         lt!-- Validate number of banana
  children in fruit_basket --gt        
  ltxslchoosegt            lt!-- Note escaped form
  of boolean gt and lt operators --gt           
  ltxslwhen test"count(banana) gt 8 and
  count(banana) lt 12"gt               lth3gt of
  banana children OKlt/h3gt           
  lt/xslwhengt            ltxslotherwisegt          
       lth3gtWhoops! of banana children is
  ltxslvalue-of select"count(banana)"/gtlt/h3gt      
        lt/xslotherwisegt        
  lt/xslchoosegt         lt!-- Set up table of info
  about banana children --gt         lttable
  border"1"gt            lttrgt              
  ltthgtbanana lt/thgt              
  ltthgtbanana_numberlt/thgt           
  lt/trgt            lt!-- Process all banana
  children of fruit_basket --gt           
  ltxslapply-templates select"banana"/gt        
  lt/tablegt     

18
DTD vs. XML Schema

• lt/bodygt   lt/htmlgt   lt/xsltemplategt
• lt!-- Process banana element(s) --gt  
  ltxsltemplate match"banana"gt      lt!-- Each
  banana element goes in its own table row --gt  
     lttrgt         ltthgtltxslvalue-of
  select"position()"/gtlt/thgt         lttdgt        
     lt!-- Test for banana's position matching
  banana_number attribute value--gt           
  ltxslchoosegt               ltxslwhen
  test"position() _at_banana_number"gt  
                 OK               lt/xslwhengt  
              ltxslotherwisegt                 
  ltstronggtWhoops!lt/stronggt... ltxslvalue-of
  select"_at_banana_number"/gt              
  lt/xslotherwisegt9557xnbo            
  lt/xslchoosegt         lt/tdgt      lt/trgt  
  lt/xsltemplategtlt/xslstyle sheetgt

19
Cascading Style Sheets

• Limitations to CSS
• Its simplicity limits more complex formatting
• Elements are processed in the order of their
  appearance
• Arithmetic operations on element positions or
  values cannot be done
• May be replaced by XSL-FO
• More detailed than CSS
• Is an XML application
• Is more closely tied to XMLs nested-container
  structure

20
XSLT (subset of XSL)

• XSLT (Extensible Style sheet Language for
  Transformation)
• Allows data in a document to be used later for
  applications that do searches, queries and other
  sophisticated operations.
• Transform a document into something else