XLink, XPointer

1
XLink,XPointer

• Boanerges Aleman Meza

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Outline

• ID, IDREF
• XLink
• XPointer
• their use in XML Databases

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ID, IDREF

• ID
• unique identifier
• IDREF, IDREFS
• reference(s) to an existing ID

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ID, IDREF
ltbibgt ltauthor idRSgtltfirstnamegtRoselt/firstna
megt ltlastnamegtSedgewicklt/lastnamegtlt/authorgt
ltauthor idTFgtltfirstnamegtTravislt/firstnamegt
ltlastnamegtForresterlt/lastnamegtlt/authorgt
ltbook authorRSgt lttitlegtAlgorithms in
Javalt/titlegt ltisbngt0-201-51059-6lt/isbngt
ltpricegt46.25lt/pricegt lt/bookgt ltbook
authorTFgt lttitlegtJava Beans
Designlt/titlegt ltisbngt0-201-54330-3lt/isbngt
ltpricegt42.25lt/pricegt lt/bookgt
lt/bibgt
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XLink

• specifies constructs to describe links
• describes a syntax for links and their
  characteristics
• uses XML namespaces for XLink vocabulary

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XLink

• Simple Links
• Backward compatible and easy
• travel from one end to another
• Extended Links
• associates an arbitrary number of resources
• resources can be remote and/or local

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XLink - Simple Links

• ltbook
• xmlnsxlink"http//www.w3.org/1999/xlink"
• xlinktype"simple"
• xlinkhref"forrester.xml" gt
• lttitlegtAlgorithms in Javalt/titlegt
• ltisbngt0-201-51059-6lt/isbngt
• ltpricegt46.25lt/pricegt
• lt/bookgt

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XLink - Simple Link Attributes

• xlinktype"simple"
• xlinkhref URI target of this link
• xlinktitle
• xlinkshow new embed replace
• xlinkactuate onRequest onLoad none
• xlinkrole description of this link
  content

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XLink - Extended Links

• ltbook
• xmlnsxlink"http//www.w3.org/1999/xlink"
• xlinktype"extended" gt
• lttitlegtAlgorithms in Javalt/titlegt
• ltisbngt0-201-51059-6lt/isbngt
• ltpricegt46.25lt/pricegt
• ( local remote )
• lt/bookgt

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Extended Links - Remote Resources

• ltreview
• xmlnsxlink"http//www.w3.org/1999/xlink"
• xlinktype"locator"
• xlinkhref"review56.xml" gt
• lt/reviewgt

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Extended Links - Local Resources

• ltreview
• xmlnsxlink"http//www.w3.org/1999/xlink"
• xlinktype"resource" gt
• ... any-content ...
• lt/reviewgt

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Extended Links

• ltbook ... gt
• ltreview ... gt
• ltreview ... gt
• ltreview ... gt
• ltreview ... gt
• lt/bookgt

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XPointer

• is built on top of the XPath (intra-document)
• extensions to XPath allow it to
• be used in URI references to address into
  resources (inter-document)
• address points and ranges as well as whole nodes
• locate information by string matching

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XPointer id(), id shourcut

• bib.xmlxptr( id( "RS" ) )
• bib.xml"RS"
• ltauthor idRSgt
• ltfirstnamegtRoselt/firstnamegt
• ltlasttnamegtSedgewicklt/lasttnamegt
• lt/authorgt

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XPointer root()

• bib.xmlxptr( / )
• ltbibgt
• ltauthorgt . . . lt/authorgt
• ltauthorgt . . . lt/authorgt
• .
• .
• ltbookgt . . . lt/bookgt
• ltbookgt . . . lt/bookgt
• .
• .
• lt/bibgt

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XPointer child
bib.xmlxptr( id( "RS" )/childfirstname )
bib.xmlRS/firstname ltfirstnamegtRoselt/firstname
gt

• bib.xmlxptr( id( "RS" )/child )
• bib.xmlRS/
• ltfirstnamegtRoselt/firstnamegt
• ltlasttnamegtSedgewicklt/lasttnamegt

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XPointer range

• bib.xmlxptr(id("RS")/range-to(id("TF")) )
• ltauthor idRSgtltfirstnamegtRoselt/firstnamegt
• ltlastnamegtSedgewicklt/lastnamegtlt/authorgt
• . . .
• ltauthor idTFgtltfirstnamegtTravislt/firstnamegt
• ltlastnamegtForresterlt/lastnamegtlt/authorgt
• resulting fragment is not guaranteed to be
  well-formed

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Comments about XLink

• over 4 years First Working draft ?
  Recommendation status
• little activity
• interest shifted to RDF and Topic Maps
• describes the way resources are presented to the
  user
• onRequest
• embed

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Their use in XML Databases

• XPointer
• not a query language
• What does it mean "support XLink ?
• In a Web Browser?
• In an XML Database?
• "support XPointer ?

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Their use in XML Databases

• ID, IDREF
• (validating parser)
• XLink / XPointer
• referential integrity ? ensure links point to
  valid documents/fragments
• query results processing ?

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References

• http//www.w3.org/TR/xlink/
• http//www.w3.org/TR/xptr/
• http//www.xml.com