Dublin Core Qualifiers and A Grammar for Dublin Core
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Transcript of Dublin Core Qualifiers and A Grammar for Dublin Core
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