XML course notes

Expand - Collapse

XML course
- http://www.vtc.com/products/introtoxml.htm
- self describing markup language
- XSL - extensible stylesheet language
  - XSLT
    - translations
    - query against original data
  - XSL-FO
    - formatting options
    - will take over from css
  - XPATH
    - language on how to write the queries
    - lets us parse through the documents
  - XLINK
    - link to a document
    - link back to original doc
    - link within current document
  - XPOINTER
    - link to a position in a file
    - eg like a href # in html
  - refer to www.w3.org to see specs on each of these + new developments
- XML basics
  - <?xml version="1.0" ?>
    - definition and spec version
      - attributes such as:
      - encoding="unicode"
        
        unicode is default if encoding character set is not specified
      - standalone="no"
        
        means this doc cannot be viewed on it's own. a translation document is required also to interpret this doc
      - standalone="yes"
        
        means the browser can display this document as is without requiring another document to translate it
    - <? ?> is a processing statement, the application or browser will process this instruction
  - <people>
    - root element
  - <husband>Mark</husband>
  - </people>
- xml editors
  - notepad / text editor
  - XML Spy
    - www.altova.com
  - XML Writer
    - www.xmlwriter.com
  - editiX
    - www.editix.com
  - morphon xml editor
    - www.morphon.com
  - emile (mac)
    - www.in-progress.com/emile
- 5 basic rules to make a well formed document
  - 1. tags are case sensitive
  - 2. opening tags must have closing tags
  - 3. tags must be properly nested
  - 4. attribute values require quotes
  - 5. root element required
- element
  - an element is a complete description of a piece of data
  - consists of the start tag, the data and the end tag
  - empty element
    - eg <br></br>
    - or <br />
- attributes
  - eg <husband employed="yes">
  - could also represent this using elements rather than as an attribute:
    <husband>
    <name>Mark</name>
    <age>45</age>
    <employed>yes</employed>
    </husband>
- values
  - make each element represent one piece of data/value only
- special characters
  - common symbols
    - < <
    - > >
    - " "
    - ' '
    - & &
    - use decimal values
      - & = &
    - CR, LF, TAB from version xml 1.0
    - xml version 1.1 can use all the ascii codes except for NUL
- comments
  - 
  - comments may be displayed or dropped from the browser or application. this is correct as per the spec
- schema
  - describes the structure of the document
  - usually the schema is a separate document
  - what data is allowed
  - what data is required
  - how data is organised
  - checks the structure of the data not the actual value of the data
- DTD or XSD
  - DTD - document type definition
    - not XML based
    - de facto standard
    - defines the XML document structure
      - defines what elements can/must appear
      - defines what order the elements must be in
      - information about the data the elements contain
      - element attributes information / requirements
      - DTD does not determine what the root element is
      - DTD does not show the number of instances of elements
      - DTD does not include the data types
      - DTD does not include the symantic meaning of an element
        
        eg whether data is a name or a date
    - can be defined inline or in a separate document (external)
    - DTD elements
      - elements are the allowed / required tags
      - created with an element declaration
        
        <!ELEMENT ElementName Type>
      - 4 types of elements
        
        empty tag - does not contain content
        
        element-only
        
        contains only child elements
        
        mixed
        
        combination of child elements and character data
        
        any
        
        any content allowed
      - DTD element options
        
        * means can appear zero or more times
        
        + means one or more times
        
        ? means zero or one time
        
        | means or
        
        no symbol means the child element must appear only once
  - XML Schema
    - XSD - XML Schema Definition
    - RELAX NG
    - W3C XML Schema Language