T. Baker / 23 Sep 2000

Dublin Core Qualifiers and

A Grammar for Dublin Core

Thomas BakerDC-8, National Library of Canada, Ottawa

4 October 2000

T. Baker / 23 Sep 2000

A pidgin for digital tourists

• Metadata is language• DC: small language -- pidgin -- for

searching across domains using a few familiar attributes

• "Pidginization": tourists learning simple phrases to order beer in an unfamiliar language

• We are all "tourists" on the global Internet.• A pidgin for using the Web to find

resources across multiple domains.

T. Baker / 23 Sep 2000

A grammar of Dublin Core

• http://www.gmd.de/People/Thomas.Baker/DC-Grammar.html

• By design not as subtle as mother tongues, but easy to learn and extremely useful in practice

• Pidgins: small vocabularies (Dublin Core: fifteen special nouns, lots of optional adjectives)

• Simple grammars: sentences (statements) follow a simple fixed pattern...

T. Baker / 23 Sep 2000

Resource has property

DC:CreatorDC:TitleDC:SubjectDC:Date...

X

implied subject

impliedverb

one of 15properties

property value(an appropriateliteral)

[optional qualifier]

[optional qualifier]

qualifiers(adjectives)

T. Baker / 23 Sep 2000

Resource has Date "2000-06-13"Revised

ISO8601

Resource has Subject "Languages -- Grammar"LCSH

T. Baker / 23 Sep 2000

Element Refinements• Make the meaning of an element narrower or more

specific.– a Date Created versus a Date Modified– an IsReplacedBy Relation versus a Replaces

Relation• A refined element shares the meaning of the

unqualified element, but with a more restricted scope.

• A client that does not understand a specific element refinement term should be able to ignore the qualifier and fall back on the broader meaning of the element.

T. Baker / 23 Sep 2000

Value Encoding Schemes• Pointers to standard encoding schemes that help

interpret or parse an element value• Says that the value is

– a term selected from a controlled vocabulary (e.g., Library of Congress Subject Headings)

– a string formatted in a standard way (e.g., "2000-01-01" as an ISO8601 expression of a date)

• If an encoding scheme is not understood by a client or agent, the value should still be "appropriate" and usable for discovery.

• Even if its scheme is unknown, a value should not be misleading.

T. Baker / 23 Sep 2000

Dumb-Down Principle for qualifiers• The fifteen elements should be usable and

understandable with or without the qualifiers• Like saying that nouns can stand on their own

without adjectives• If your search engine encounters an unfamiliar

qualifier, look it up somewhere -- or just ignore it!

• To test whether a qualifiers are "good", cover the qualifiers with your hand and ask:– Does the statement still make sense?– Is it correct?

T. Baker / 23 Sep 2000

Resource has Date "2000-06-13"Revised

ISO8601

Resource has Subject "Languages -- Grammar"LCSH

T. Baker / 23 Sep 2000

Review and approval status

• DCMI Usage Committee reviews proposals for qualifiers

• Evaluates proposals in light of grammatical principles (are the qualifiers ignorable?)

• Tiered model of approval status (tentative): proposed, conforming, recommended, obsolete

T. Baker / 23 Sep 2000

History of a new process• 1998, Nov: DC-7, element-specific

working groups form to propose useful qualifiers

• 1999, Oct: DC-8, breakout groups review proposals against principles; the Usage Committee forms

• 2000, Jan: intended deadline passes• 2000, Feb: formal principles reformulated

in Usage Committee• 2000, Jul: first qualifiers are published

T. Baker / 23 Sep 2000

A not-so-good example

Resource has Creator "Last.name: Smith

First.name: John

Type: Person

Affiliation: IBM"

T. Baker / 23 Sep 2000

Value Components: proposed as a third type of qualifier -- and rejected

Property PropertyProperty Property

Type Title Date Creator

Information resource

HASA

HA

SA

HA

SA

HASA

"J.Smith"

VC VC

HA

SAHASA

Type

"Person"

Affiliation

"IBM"

T. Baker / 23 Sep 2000

Perhaps we should move them to...

Element ElementElement Element

Type Title Date Creator

Information resource

HASA

HA

SA

HA

SA

HASA

"J.Smith"

VC VC

HA

SAHASA

Type

"Person"

Affiliation

"IBM"

T. Baker / 23 Sep 2000

...a Core Element Set for Agents?

Property

Name

PropertyProperty Property

Value

Type Affiliation Birthdate Name

Person (or Corporation)

"J.Smith" "IBM" "Person" "1947-03-30"

HASA

HA

SA

HA

SA

HASA

T. Baker / 23 Sep 2000

Richer metadata languages• Complexification compromises the pidgin• Richer vocabularies and grammatical

structures needed for describing multiple related entities (resources, the people who created them, their life-cycle events...)

• Plenary II: Modular management of complexity– Application profiles– Structured metadata for richer description

• DCMI Architecture Working Group

T. Baker / 23 Sep 2000

thomas.baker@gmd.de