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Schemas or Vocabularies?

April 26, 2005

OASIS Symposium on the Future of XML Vocabularies

Bob DuCharme

LexisNexis

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Outline

• review Dublin Core

• “vocabularies”

• creating vocabularies (and maybe schemas): required and optional steps

• case study: PRISM

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Dublin Core• Dublin Core Metadata Initiative• dublincore.org• DCMI Metadata Terms: elements, element

refinements, encoding schemes, and vocabulary terms

• element: “A discrete unit of data or metadata. An element may contain subelements that are called qualifiers in Dublin Core. ”

• creator, date, description, format, identifier…

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“vocabulary”?

• list of words?

• DTD?

• schema? – W3C Schema? – RELAX NG schema?– RDF Schema?

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Mandatory step 1

Define your standard list of words:

• The actual words to use (PublishDate? publish-date?

PubDate?)

• Their meanings.

• (optional) Value restrictions, e.g.

– formatting, such as ISO 8601 for dates

(“2005-04-26T09:20”)

– list of values to choose from (Y/N, True/False, ISO 3166 country codes)

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Example Dublin Core definition

Term Name: format

URI: http://purl.org/dc/elements/1.1/format

Label: Format

Definition: The physical or digital manifestation of the resource.

Comment: Typically, Format may include the media-type or dimensions of the resource. Format may be used to determine the software, hardware or other equipment needed to display or operate the resource. Examples of dimensions include size and duration. Recommended best practice is to select a value from a controlled vocabulary (for example, the list of Internet Media Types [MIME] defining computer media formats).

Reference: [MIME] http://www.iana.org/assignments/media-types/

Type of Term:

element

Status: recommended

Date Issued: 1999-07-02

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Optional Steps 2 and 3

• Figure out the relationships of your labeled pieces of information

• Write it down in a machine-readable form

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RDF Schemas

“RDF user communities also need the ability to define the vocabularies (terms) they intend to use in those statements, specifically, to indicate that they are describing specific kinds or classes of resources, and will use specific properties in describing those resources…”

- W3C RDF Tutorial

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Validation?

“RDF classes and properties are in some respects very different from programming language types. RDF class and property descriptions do not create a straightjacket into which information must be forced, but instead provide additional information about the RDF resources they describe.”

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Flexibility

• advantage: more systems can adapt, politically easier to sell

• disadvantage: fuzziness, more work to adopt a standard

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PRISM

• Publishing Requirements for Industry Standard Metadata

• “Developing a standard XML metadata vocabulary for the publishing industry”

• http://www.prismstandard.org

• v 1.0: 2001; current version: 1.2

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PRISM 1. 2 “elements”General Purpose

Provenance Dates and Time Subject

Description

Relations Rights Controlled

Vocabs

Inline Markup

dc:

identifier

title

creator

contributor

description

language

format

type

prism:

category

dc:

publisher

source

prism:

distributor

edition

issn

issueName

number

startingPage

Volume

prism:

creationDate

expirationDate

modificationDate

publicationDate

releaseDate

receptionDate

dc:

coverage

subject

prism:

event

industry

location

person

organization

section

prism:

isCorrectionOf

hasCorrection

isPartOf

hasPart

isVersionOf

hasVersion

isFormatOf

hasFormat

References

isReferencedBy

isBasedOn

isBasisFor

isTranslationOf

hasTranslation

requires

isRequiredBy

isAlternativeFor

hasAlternative

dc:

rights

prism:

copyright

expirationTime

releaseTime

rightsAgent

prl:

geography

industry

usage

pcv:

broaderTerm

code

definition

Descriptor

label

narrowerTerm

relatedTerm

synonym

Vocabulary

pim:

event

industry

location

objectTitle

organization

person

quote

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PRISM DTDs

• metadata vs. data:– article titles, bylines– identifying inline entities

• PRISM Aggregator DTD (PAM)

• Two levels of compliance– level one: well-formed XML, dc:identifier– level two: RDF profile, rdf:about

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PRISM RDF Schema

• Tony Hammond, Nature Publishing Group

• under “contributed resources” on PRISM website

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Lessons Learned

• Which works best for your industry: vocabulary, DTD, XSD, RNG…

• Layered approach a good option

• Say what you mean

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Schemas or Vocabularies?

April 26, 2005

OASIS Symposium on the Future of XML Vocabularies

Bob DuCharme

LexisNexis