Pervasive ecommerce with XML

1
Pervasive e-commerce with XML

• Babak Esfandiari
• Carleton University
• Ottawa, Canada

2
XML introduction

• eXtensible Markup Language
• a markup language for documents containing
  structured information (Walsh)
• this structure is defined mainly with a set of
  tags
• subset of SGML
• HTML can be seen as an instance of XML (it is not
  really though, but that is not important)

3
XML example

• lt?xml version"1.0" ?gt
• lt!-- a simple tagset for museumsgt
• ltMuseum name"Louvre"gt
• ltcitygt Paris
• lt/citygt
• lt/Museumgt

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DTD

• Document Type Definition
• Describes the XML tagset
• lt!DOCTYPE Museum
• lt!ELEMENT Museum (city)gt
• lt!ATTLIST Museum name CDATA REQUIREDgt
• lt!ELEMENT city (PCDATA)gt
• gt
• Not mandatory (!)

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XML - what for?

• content is independent from rendering
• meta-data makes search easier
• standard tags enable data interchange across
  tools
• format for data and object persistence, human
  readable and editable
• no need for a custom parser anymore

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TourTags

• The purpose of TourTags.org is to foster
  dialogue within the community in order to arrive
  at open standards for conducting electronic
  commerce by settling on common tag sets and
  methods in which they are to be used.
• supports IFITTs RMSIG

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XML and TourTags

• derive a tagset from RMSIG specs
• discuss/modify the tagset
• use the tagset for B2B (ebXML)
• allow device-neutral access to business info
• we have a process

8
The Acronym Hell Diagram

• our process is a series of transformations

HTML
UML
ebXML
XML
WML
XMI
Web form
Voice XML
XML/ DTD
registration
document
display
meta-data
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Meta-data

• Why not directly model tags?
• Tags are not for modeling!
• Lack of a graphical notation
• Semantically poor
• Hard to represent relationships
• XML can be seen as one possible mapping of a
  model
• The RMSIG has chosen UML

UML
XMI
XML/ DTD
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Meta-data

• UML Unified Modeling Language
• Object-oriented
• Graphical
• Covers
• Requirements
• Static representation
• Activities and processes

UML
XMI
XML/ DTD
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Meta-data

• A UML class diagram

UML
XMI
XML/ DTD
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Meta-data

• But we need the tags!
• Is it possible to transform UML into XML?
• We can use XMI
• XMI is the direct textual representation of UML
  using the XML format
• Most UML tools support XMI

UML
XMI
XML/ DTD
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Meta-data

• A sample XMI document
• ltClassgt
• ltnamegtMuseumlt/namegt
• ltfeaturegt
• ltAttributegt
• ltnamegtnamelt/namegt
• lt/Attributegt
• lt/featuregt
• lt/Classgt

UML
XMI
XML/ DTD
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Meta-data

• We still need to transform XMI into our XML
  tagset
• Since a DTD describes the structure of an XML
  document, it is the ideal target!
• What is the easiest way to do the concrete
  transformation?

UML
XMI
XML/ DTD
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Transformations

• Different methods
• Parsing use existing XML parsing libraries based
  on standard APIs (SAX, DOM) with a programming
  language
• Transformations
• specify the transformations in a (yet another)
  XML document called an XSLT stylesheet
• Use an XSLT processor (Saxon, XT, )

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XSLT example (excerpt)

• ltxslstylesheetgt
• ltxsltemplate match"Class"gt
• blah ltxslvalue-of select"name"/gt blah
• ltxslapply-templates select"feature/Attribute"/gt
  
• lt/xsltemplategt
• ltxsltemplate match"feature/Attribute"gt
• ltxslvalue-of select"name"/gt
• lt/xsltemplategt
• lt/xslstylesheetgt

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XSLT example

• The XSLT in the previous slide, applied on the
  Museum XMI, should generate something like
• blah Museum blah name
• Nothing exciting but you get the idea!

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Meta-data

• Some of the issues in the transformation from XMI
  to DTD
• Ambiguity in choice of attributes and elements -gt
  open for discussion!
• Inheritance compound the inherited attributes
• Composition recursively add sub-elements, or use
  separate documents
• DTDs support for primitive types is limited XML
  schema an alternative

UML
XMI
XML/ DTD
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Registration

• The resulting DTDs can now be used for B2B
  e-commerce
• We now have a domain ontology to base
  transactions on!
• We can use this ontology to
• Publish/advertize a business
• Search for a business
• We need a registry to enable that

ebXML
Web form
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Registration

• ebXML is one of the leading consortiums for
  e-business
• It describes a standard for B2B registries
• Third parties (TourTags?) have the opportunity to
  create and host such registries
• To access such registries and allow publishing
  and search, Web forms are an intuitive front-end
  interface
• Guess what

ebXML
Web form
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Registration

• We can use the DTDs and XSLT to generate such web
  forms!
• The web forms for publishing and search are very
  similar
• Each leaf element or attribute becomes a field to
  fill in
• Better support (than DTDs) for data types would
  allow for a better customization of the data
  fields

ebXML
Web form
Museum name
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Registration

• Different deployment scenarios are possible for
  registries
• Traditional Client/server
• Peer to peer
• Decentralized
• Less resource intensive

ebXML
Web form
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Document rendering

• The result of a registry search is an XML
  document that follows the structure specified by
  our DTD
• Such a document does not contain any instructions
  for rendering (i.e. display)
• This is a good thing!

HTML
XML
WML
Voice XML
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Search and rendering

• rendering adapted to device
• XML -gt HTML for web browser
• XML -gt WML for cell phones
• XML -gt VoiceXML for regular phones
• Yes, we can use XSLT again!
• No duplication of data!
• No need to maintain redundant documents!

HTML
XML
WML
Voice XML
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Conclusion

• A completely XML-based process that takes us from
  the inception of a domain ontology to the
  delivery of business info
• The process relies on a series of transformations

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References

• xml.org
• rmsig.org
• tourtags.org
• ebxml.org
• It had to be on the web!