PRACTICAL KNOWLEDGE REPRESENTATION FOR THE WEB Frank van Harmelen Dieter Fensel AIFB Kim Kangil Structural Complexity Laboratory

CONTENTS Existing Semantic mark-up languages Symbol level comparison Knowledge level comparison conclusion

EXISTING SEMANTIC MARKUP LANGUAGES HTML based HTML - tags SHOE HTML derived HTML - elements ; Ontobroker Cascading Style Sheets XML RDF

HTML -TAGS

SHOE

HTML -ELEMENTS

ONTOBROKER

CASCADING STYLE SHEETS

PROPERTIES -tag Global property Anchor mechanism SHOE Extension of meta tag Independent to location Arbitrary relation number Global property

-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 : non-standard, anchor mechanism : duplicated, : use same information for rendering and adding semantic information : separation is intened

ALLOWING NESTING & SUPPORTING WEB TECHNOLOGY In language design, Nesting of expression is the typcial way to use the scoping Xml, CSS, 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