CM322: Advanced Web Technologies

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CM322 Advanced Web Technologies
Verifying XML with DTDs Les Carr IAM Research
University of Southampton
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Session 2

• XML Verification
• DTDs and Valid XML
• XML Namespaces
• Example XML Vocabulary SMIL

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XML Verification

• Well-formed XML document
• conforms to basic XML syntax
• contains only built-in character entities
• Validated XML document
• conforms to the grammar of a specific data type
• uses any predeclared entities
• specified by Document Type Declaration

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XML Type Declaration

• A DTD specifies the grammar for a simple data
  structure
• ordering
• repeatability
• labelling
• vocabulary / schema / ontology
• DTD defined in an external entity
• overridden by local definitions

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XML Type Declaration

• Element declarations
• lt!ELEMENT para contents of paragt
• just text
• lt!ELEMENT para (PCDATA)gt
• ltparagtHere is some text. No italics
• allowed.lt/paragt

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XML Type Declaration

• just a sequence of elements
• lt!ELEMENT person (name, email, phone)gt
• ...
• ltpersongt
• ltnamegtLeslt/namegt
• ltemailgtlac_at_ecs.soton.ac.uklt/emailgt
• ltphonegt44 23 8067 5145lt/phonegt
• lt/persongt

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XML Type Declaration

• just a choice of elements
• lt!ELEMENT person (name email staffno)gt
• ...
• ltpersongt
• ltnamegtLeslt/namegt
• lt/persongt

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XML Type Declaration

• element repetition can be controlled
• ? optional
• required and repeatable
• optional and repeatable
• element can be grouped with ( )
• lt!ELEMENT customer (
• ((surname, initials) custid),
• purchases , visits )gt

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XML Type Declaration

• mixed content (text interspersed with elements)
• lt!ELEMENT para
• (PCDATA italic bold
• link image)
• -- optional repeatable choice group
• with PCDATA as first item --
• gt

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XML Type Declaration

• no content
• lt!ELEMENT image EMPTY gt
• any content
• lt!ELEMENT buffer ANY gt

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XML Type Declaration

• Attribute declarations
• lt!ATTLIST para
• security security attribute info
• author author attribute info
• id id attribute info gt
• Each attribute has a type and default
• lt!ATTLIST para
• security (privatepublic) "public"
• author CDATA IMPLIED
• id ID REQUIRED gt

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XML Type Declaration

• Attribute types
• CDATA, NMTOKEN(S), ENTITY(-IES), ID, IDREF(S),
  enumeration
• Default values
• string
• token
• IMPLIED
• REQUIRED
• FIXED (must precede default)

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XML Entities

• Entities can be strings
• lt!ENTITY cc "Clifford Chance"gt
• Entities can be external files
• Entities can be binary data formats
• lt!ENTITY pic1 SYSTEM "me.gif" NDATA gifgt
• lt!NOTATION gif SYSTEM "gifviewer.exe"gt

lt!ENTITY chap1 SYSTEM "../src/ch1.xml"gt lt!ENTITY
disc PUBLIC "-//CC//Standard Disclaimer//EN"
"/lib/stddisc.xml"gt
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XML Entities

• Entities must be declared in a DTD
• lt!DOCTYPE Book
• lt!ENTITY chap1 SYSTEM "ch1.xml"gt
• gt
• Entities can be used in text or attributes
• ltbookgtchap1 chap2 chap3lt/bookgt
• ltpara title"This amp That"/gt
• ltimage src"pic1" alignleft/gt

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XML Entities

• Parameter entities provide macro expansion within
  a DTD
• use '' instead of ''
• prefix name by '' in declaration
• lt!ENTITY common "name address phone"gt
• lt!ELEMENT stuff ( common email )

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XML Namespaces

• Namespaces allow different designers to create
  different elements and attribute names for
  different purposes.
• e.g. MS catalogue
• lttablegt element for screen layout
• lttablegt element for describing furniture

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XML Namespaces

• Namespace is identified with a URL
• Namespace is referred to by a prefix
• Any name from that namespace is referred to by a
  qualified name
• prefixname
• e.g. lthtmltablegt
• or ltpara MoDclassificationrestrictedgt

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XML Namespaces

• Namespace is defined
• at the document root
• by the xmlns attribute prefix
• ltcatalog xmlnshtml"http//www.w3c.org/TR/REC-htm
  l40"gt
• lthtmltablegt
• lttable materialpinegtltpricegt120lt/pricegtlt/tablegt
• ltchair materialpinegtltpricegt34lt/pricegtlt/chairgt
• lt/htmltablegt
• lt/cataloggt

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SMIL

• W3C Standard for Synchronised Multimedia
• XML format
• regions
• sequences
• parallels
• audio, video
• pictures

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SMIL

• ltsmilgt
• ltbodygt
• ltseq id"Herengracht_Stroll"gt
• ltimg id"map" src"map.gif" dur"3s"/gt
• ltimg id"hg168" src"h168.gif" dur"3s"/gt
• ltimg id"hg218" src"h218.gif" dur"3s"/gt
• ltimg id"hg284" src"h284.gif" dur"3s"/gt
• lttext type"text/plain" id"Credits"
• src"dataThanks20to..." dur"indefinite"/gt
• lt/seqgt
• lt/bodygt
• lt/smilgt

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SMIL

• Vocabulary
• regions are spaces on the display device
• seqs are sequential orderings of
• pictures, sounds, videos, text
• all of which appear one after the other
• pars are parallel orderings of
• pictures, sounds, videos, text
• all of which appear at the same time

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SMIL

• Constraints
• each content item must appear in a region
• each picture, video etc is assigned a duration
• seq duration is sum of media durations
• finishes when last element has completed
• par duration is max of media durations
• finishes when longest element has completed

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SMIL

• Vocabulary gets quite complex!
• DTD has to reflect this

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References

• XML Applicationshttp//www.oasis-open.org/cover/
  xml.htmlapplications
• XML Namespaces by Examplehttp//www.xml.com/xml/p
  ub/1999/01/namespaces.html
• SMILhttp//www.w3.org/AudioVideo

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Exercise 1

• The simple XML file book.xml has a DTD in
  books.dtd
• Use the validator and the DTD to help correct the
  errors in badbooks.xml

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Exercise 2

• Write a DTD for the well-formed XML document you
  created in the previous session.
• Use validate.html to check it in Explorer as
• an external entity
• an internal subset

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Exercise 3

• The files day1.xml, day2.xml and day3.xml
  describe three days out, giving various
  activities and breaks from an E-travel-agency.
• Construct a DTD that can be used to validate all
  three files.