XML: XPath XLINK

1
XML XPath XLINK

• Spring 2002
• Dr. Sergio Davalos

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XML Path Language XPATH

• View XML document as a tree
• Directory/subdirectories/files
• Nodes
• Node types root, element, attribute, text,
  comment, processing instruction, namespace
• XPath tree root node/ root node and element
  nodes contain lists of child nodes
• Child nodes are element, comment, text,
  processing instruction
• Attribute and namespace describe the environment
  in which the parent node
• Figure 11.2
• Descendent text nodes
• Document order
• Figure 11.4

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Other

• Location Path expression for navigating a tree
  from node to node sequence of location steps
• Axes
• Context node
• Content for searching
• Forward axes, reverse axes
• Node test refine set of selected nodes
• Location path using axes and node tests
• Axisnotest for predicate
• Child -select all child of context node
• Childtext() all text elements child
• Child/childtest() grandchildren of context
  node
• Body all element body of context node
• //body for /descendent-or-
• selfnode()/childbody

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Continued

• Head body
• Union of two children element nodes of the
  context nod
• Head/title last() - uses the predicate last
  to select the last bold element contained in the
  head element
• Pointers within XSL, XSLT

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XLINK, XPointer, XInclude, Xbase

• Hypertext
• XLINK
• XLINK and DTDs
• XPointer
• XML Inclusions
• XML XBase (XBASE)

6
Hypertext

• What is it linked segments of information
• Link names and Types
• Power of links
• Problems navigation, searching
• Compromise XLINK

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XLINK

• HTML link a element and href
• XML linking language XLINK
• XLINK links resources documents, audio, video,
  db.
• Movie could be linked to its sound track
• Song linked to information about the artist
• Available when information is accessed - song
  played
• Link to a set of resources

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XLINK

• Simple links
• ltbook xlinktypesimple xlinkhref/textbooks/x
  mlHowToProgram.xmlgt
• Local resource links to remote resource
• Use an arc

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XLINK

• ltbook
• xlinktypesimple
• xlinkhrefabout.xml
• xlinkrolehttp//www.davalos.com/xlink/contact
• Xlinktitle gt
• Role is a URI that references a resources that
  describes the link
• Title descriptive title for the link
• Figure 14.2 page 375

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Figure 14.4

• ltbook
• xlinktypesimple
• xlinkhrefabout.xml
• xlinkrolehttp//www.davalos.com/xlink/contact
• xlinktitle About S. Davalos
• xlinkshow new
• XlinkactuateonRequestgt
• Role is a URI that references a resources that
  describes the link
• Title descriptive title for the link
• Show new display resource in new window
• Replace (replace current resource, embed
  replace current element, other, none
• Actuate - onRequest, onLoad, other, none

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Extended links

• Extended links multiple combinations of local
  and remote resources
• Unidirectional
• multidirectional (go back) - access all links to
  all linked documents Figure 14.7
• Figure 14.8 (rendered 14.9)
• ltauthor xlinklabel authorDeitel identifies
  the resource
• arcrole -
• to
• from
• type locator where resources located
• - resource local resource

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XLINK

• Arc information
• ltarcElement
• xlinktype arc
• XlinkfromJavaBook
• Xlinkarcrolehttp//deitel.com/xlink/info
• Xlinkto authorDeitel

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XLINK and DTDs

• Can define links in DTD
• Figure 14.13

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XPointer

• Use XPointer to link specific parts of a resource
• Specific locations (nodes in a XPath tree) or
  ranges of location in an XML document
• pointerlocation within the document

15
XML Inclusions

• XInclude include one XML in another