PRACTICAL KNOWLEDGE REPRESENTATION FOR THE WEB
Frank van Harmelen Dieter Fensel AIFB
Kim KangilStructural Complexity Laboratory
CONTENTS
Existing Semantic mark-up languages
Symbol level comparison
Knowledge level comparison
conclusion
EXISTING SEMANTIC MARKUP LANGUAGES
HTML based HTML <META> - tags SHOE
HTML derived HTML <SPAN> - elements ; Ontobroker Cascading Style Sheets
XML RDF
HTML <META>-TAGS
SHOE
HTML <SPAN>-ELEMENTS
ONTOBROKER
CASCADING STYLE SHEETS
PROPERTIES
<meta>-tag Global property Anchor mechanism
SHOE Extension of meta tag Independent to location Arbitrary relation number Global property
<span>-elements Standard CLASS attribute, Structure for giving semantic is in a document
Ontobroker First order logic Similar to span-tag
CSS to separate structure information Style specification Can be used for adding semantic information
XML
-A Labeled tree-Nesting-DTD
RDF
-Data model -Resource-Property-Statement
-No assumption to add structural information ?- XML schema base
SYMBOL COMPARISON
Support of web technology
Avoiding duplication
Allowing nesting
AVOIDING DUPLICATION
Removing the duplicated expression to add semantic information and to render that
Reducing the cost to use in the Web
<meta> : non-standard, anchor mechanism <SHOE> : duplicated <XML>,<SPAN-tag> : use same information for
rendering and adding semantic information <RDF> : separation is intened
ALLOWING NESTING & SUPPORTING WEB TECHNOLOGY
In language design, Nesting of expression is the typcial way to use the scoping Xml, CSS, <SPAN> can support nesting RDF can’t support nesting with natural way
Supporting web technology means how well some languages can be spread out for using AI on the web Syntactical variety can be harmful to be
supported, ex. SHOE,Ontobroker
KNOWLEDGE COMPARISON
Factual knowledge : Data–model
Terminological knowledge : ontology
Inferential knowledge
FACTUAL KNOWLEDGE : DATA MODEL Various data model type
Meta-tag : basic html attribute mechanism XML & Span-tag : labeled trees Ontobroker : expression in F-logic , complicated
expression could be included to onto- attribute. Multiple inheritance of attributes.
RDF : use binary relation. extended by reificatoin SHOE : n-ary relation. Use attribute for classes,
multiple inheritance of attributes
RDF, Ontobroker, SHOE support object oriented type schema
RDF is property-centric ( don’t use attribute ) – don’t refine when it is inherited to sub classes. Sharing property is impossible
TERMINOLOGICAL KNOWLEDGE : ONTOLOGY
Specification of conceptualization vocabulary to describe domain.
Meta,span-tag is not making data-schema separately.
CSS make it , but just a list of category names. SHOE, Ontobroker provide explicit ontology.
Ontobroker has single centrally defined ontology. But SHOE could extend ontology locally.
DTD of xml is close to ontology,but just lexical nesting specification. Missing : ontological hierachical specification,
inheritance mechanism, range restrictions on attribute. RDF can describe ontology but, it needs
reification
INFERENCE KNOWLEDGE
SHOE : pure HORN rules Ontobroker : first order logic fragments Other things impossible. ?
CONCLUSION
On the symbol comparison , span-tag has much of functionality of XML
On the knowledge comparison, META and SPAN-tag is not rich. Surprising thing is, RDF and XML also don’t support to use ontology and inference
For using AI on realistic, large-scale Web application, Span-tag will good to support it.
RDF needs more development for representing ontology, inferential knowledge
Essentially, SHOE, Ontobroker ,these two AI based language is useful on the knowledge level feature
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