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