Ora Lassila Research Fellow, Nokia Research Center December 2000

1 © NOKIA 04/19/23 - Ora Lassila

“I Was There…” – Memoirs of anRDF Working Group Member

or

Observations about theRDF Design Rationale

Ora Lassila

Research Fellow, Nokia Research Center

December 2000


RDF Timeline

1997 Spring Pre-WG work (e.g., PICS-NG), “authors’ meeting” @ MIT

1997 Summer M+S Working Group chartered, M+S first draft (for group review)

1997 October M+S first public draft

1997 November RDFS Working Group chartered

1998 April RDFS first draft (for group review)

1998 October M+S goes to “last call”

1999 January M+S goes to proposed recommendation

1999 February M+S goes to recommendation!

1999 March RDFS goes to proposed recommendation

1999 August RDF Interest Group formed

1999 October The “Cambridge Communiqué” published

2000 March RDFS goes to candidate recommendation


Motivation

• library metadata (Dublin Core)

• content rating (PICS)

• site maps

• some other applications…


Model

• Ora (from PICS-NG): frame-like model

• Guha: understanding which statements have been asserted, and which ones have not

• WG charter included mandatory PICS support• certain features, which cannot really be implemented in the model

itself, crept in (“aboutEachPrefix”)

• Acceptance & deployment was very important• “just simple enough” for the WWW community at large to accept

and deploy• “not too offensive” for the KR community so it could be used as a

starting point for something better• main challenge: managing expectations


Syntax

• Naming (e.g., “Pumpkin”)

• S-expressions vs. XML• in some sense, the choice of XML was an unfortunate one, because

it leads to a lot of confusion

• Namespaces were deemed necessary, and consequently an XML NS spec which supports RDF needs was “rammed through” at W3C

• issues with the namespace of attributes like “about”

• Interpretation of literals• XML Schema was supposed to provide “primitive” datatypes


Details, Details, Details, …

• RDF is supported by a number of other standards• XML• URI• HTTP (caching semantics)• …

• It is important to understand that RDF takes care of a lot of “dirty details” which we now no longer have to worry about


Type System & Ontology - RDF Schema

• Basic definition of “Class”• defined as a prototype rather than a classification

• Metaclass issues proved to be hard• ANSI X3J13 as an inspiration, but simplified• class Class and “class Metaclass” are the same thing

• “DisjointWith” and cardinalities: discussed but eventually rejected

• Domain & range proved to be hard (for the WG)• “subPropertyOf” vs. “subClassOf”


“Mysteries” of Domain & Range

y x

p c

type

domain Class

type

type

Property

type

type

type


Other Issues

• “Dueling press releases”• Netscape’s love for RDF vs. Microsoft’s marketing message• a lot of the RDF M+S work happened at the height of the so-called

“browser wars”

• WG member troubles• skill/experience vs. technical complexity mismatch

• RDFS vs. XML Schema• cf. the “Cambridge Communiqué”• RDFS still not a recommendation…


Questions?

• mailto:[email protected]

• mailto:[email protected]

Lauren Lassila (age 3 months) finds the RDF DesignRationale a perfect bedtime story.

yawn…

Ora Lassila Research Fellow, Nokia Research Center December 2000

Documents

Transcript of Ora Lassila Research Fellow, Nokia Research Center December 2000