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CS/INFO 430Information Retrieval

Lecture 20

Metadata 2

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Course Administration

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Cataloguing Online Materials: Dublin Core

Dublin Core is an attempt to apply cataloguing methods to online materials, notably the Web.

History

It was anticipated that the methods of full text indexing that were used by the early Web search engines, such as Lycos, would not scale up.

"... [automated] indexes are most useful in small collections within a given domain. As the scope of their coverage expands, indexes succumb to problems of large retrieval sets and problems of cross disciplinary semantic drift. Richer records, created by content experts, are necessary to improve search and retrieval."

Weibel 1995

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Dublin Core

Simple set of metadata elements for online information

• 15 basic elements

• intended for all types and genres of material

• all elements optional

• all elements repeatable

Developed by an international group chaired by Stuart Weibel since 1995.

(Diane Hillmann of Cornell has been very active in this group.)

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QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

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Dublin Core record for the Dublin Core Web Site

contributor: Dublin Core Metadata Initiative

description: The Dublin Core Metadata Initiative is an open forum engaged in the development of interoperable online metadata standards that support a broad range of purposes and business models...

title: Dublin Core Metadata Initiative (DCMI) Home Page

date: 2004-10-05

format: text/html (MIME type)

language: en (English)

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Dublin Core elements

Element Name: Title

Definition: A name given to the resource.

Comment: Typically, Title will be a name by which the resource is formally known.

Element Name: Creator

Definition: An entity primarily responsible for making the content of the resource.

Comment: Examples of Creator include a person, an organization, or a service. Typically, the name of a Creator should be used to indicate the entity.

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Dublin Core elements

Element Name: Subject

Definition: A topic of the content of the resource.

Comment: Typically, Subject will be expressed as keywords, key phrases or classification codes that describe a topic of the resource. Recommended best practice is to select a value from a controlled vocabulary or formal classification scheme.

Element Name: Description

Definition: An account of the content of the resource.

Comment: Examples of Description include, but is not limited to: an abstract, table of contents, reference to a graphical representation of content or a free-text account of the content.

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Dublin Core elements

Element Name: Publisher

Definition: An entity responsible for making the resource available

Comment: Examples of Publisher include a person, an organization, or a service. Typically, the name of a Publisher should be used to indicate the entity.

Element Name: Contributor

Definition: An entity responsible for making contributions to the content of the resource.

Comment: Examples of Contributor include a person, an organization, or a service. Typically, the name of a Contributor should be used to indicate the entity.

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Dublin Core elements

Element Name: Date

Definition: A date of an event in the lifecycle of the resource.

Comment: Typically, Date will be associated with the creation or availability of the resource. Recommended best practice for encoding the date value is defined in a profile of ISO 8601 [W3CDTF] and includes (among others) dates of the form YYYY-MM-DD.

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Dublin Core elements

Element Name: Type

Definition: The nature or genre of the content of the resource.

Comment: Type includes terms describing general categories, functions, genres, or aggregation levels for content. Recommended best practice is to select a value from a controlled vocabulary (for example, the DCMI Type Vocabulary [DCT1]). To describe the physical or digital manifestation of the resource, use the FORMAT element.

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Dublin Core elements

Element Name: 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 identify 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).

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Dublin Core elements

Element Name: Identifier

Definition: An unambiguous reference to the resource within a given context.

Comment: Recommended best practice is to identify the resource by means of a string or number conforming to a formal identification system. Formal identification systems include but are not limited to the Uniform Resource Identifier (URI) (including the Uniform Resource Locator (URL)), the Digital Object Identifier (DOI) and the International Standard Book Number (ISBN).

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Dublin Core elements

Element Name: Source

Definition: A Reference to a resource from which the present resource is derived.

Comment: The present resource may be derived from the Source resource in whole or in part. Recommended best practice is to identify the referenced resource by means of a string or number conforming to a formal identification system.

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Dublin Core elements

Element Name: Language

Definition: A language of the intellectual content of the resource.

Comment: Recommended best practice is to use RFC 3066 [RFC3066] which, in conjunction with ISO639 [ISO639]), defines two- and three-letter primary language tags with optional subtags. Examples include "en" or "eng" for English, "akk" for Akkadian", and "en-GB" for English used in the United Kingdom.

Element Name: Relation

Definition: A reference to a related resource.

Comment: Recommended best practice is to identify the referenced resource by means of a string or number conforming to a formal identification system.

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Dublin Core elements

Element Name: Coverage

Definition: The extent or scope of the content of the resource.

Comment: Typically, Coverage will include spatial location (a place name or geographic coordinates), temporal period (a period label, date, or date range) or jurisdiction (such as a named administrative entity). Recommended best practice is to select a value from a controlled vocabulary (for example, the Thesaurus of Geographic Names [TGN]) and to use, where appropriate, named places or time periods in preference to numeric identifiers such as sets of coordinates or date ranges.

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Dublin Core elements

Element Name: Rights

Definition: Information about rights held in and over the resource.

Comment: Typically, Rights will contain a rights management statement for the resource, or reference a service providing such information. Rights information often encompasses Intellectual Property Rights (IPR), Copyright, and various Property Rights. If the Rights element is absent, no assumptions may be made about any rights held in or over the resource.

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Qualifiers

Example: element qualifier

Example: Date

DC.Date.Created 1997-11-01

DC.Date.Issued 1997-11-15

DC.Date.Available 1997-12-01/1998-06-01

DC.Date.Valid 1998-01-01/1998-06-01

A qualifier refines the element name to add specificity

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Qualifiers

Example: value qualifiers

Example: Subject

DC.Subject.DDC 509.123 (Dewey Decimal Classification)

DC.Subject.LCSH Digital libraries-United States(Library of Congress Subject Heading)

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Dumbing Down Principle

"The theory behind this principle is that consumers of metadata should be able to strip off qualifiers and return to the base form of a property. ... this principle makes it possible for client applications to ignore qualifiers in the context of more coarse-grained, cross-domain searches."

Lagoze 2001

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Dumbing Down Principle

Qualified version

DC.Date.Created 1997-11-01

DC.Subject.LCSH Digital libraries-United States

Dumbed-down version

DC.Date 1997-11-01 a valid date

DC.Subject Digital libraries-United States a valid subject description

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Dublin Core with qualifiers

See the next two slides for an example of a Dublin Core record for a web site prepared by a professional cataloguer at the Library of Congress.

Note that the record does not follow the principle of dumbing-down.

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Theoretical Problems in Metadata: What to Catalog

The IFLA Model

Work A work is the underlying abstraction, e.g.,

• The Iliad

• The Computer Science departmental web site

• Beethoven's Fifth Symphony

• Unix operating system

• The 1996 U.S. census

This is roughly equivalent to the concept of "literary work" used in copyright law.

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IFLA Model

Expression. A work is realized through an expression, e.g.,

• The Illiad has oral expressions and written expressions

• A musical work has score and performance(s).

• Software has source code and machine code

Many works have only a single expression, e.g. a Web page, or a book.

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IFLA Model

Manifestation. A expression is given form in one or more manifestations, e.g.,

• The text of The Iliad has been manifest in numerous manuscripts and printed books.

• A musical performance can be distributed on CD, or broadcast on television.

• Software is manifest as files, which may be stored or transmitted in any digital medium.

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IFLA Model

Item. When many copies are made of a manifestation, each is a separate item, e.g.,

• a specific copy of a book

• computer file

[Works, expressions, manifestations and items are explored in CS 431, Architecture of Web Information Systems.]

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Theoretical Problems in Metadata: : Events

Version 1

New material

Version 2

Should Version 2 have its own record or should extra information be added to the Version 2 record?

How are these represented in Dublin Core or MARC?

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Theoretical Problems in Metadata: : Complex Objects

Complex objects

• Article within a journal• Page within a Web site• A thumbnail of another image• The March 28 final edition of a newspaper

Complete object

Sub-objects

Metadata records

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Theoretical Problems in Metadata: Packaging Rules

When an object consists of various parts, how should their interaction be described?

Example: An object on the Web may consist of several html pages with images, applets, etc.

Metadata Object Description Schema (MODS)http://www.loc.gov/standards/mods/

MPEG 21http://www.chiariglione.org/mpeg/standards/mpeg-21/mpeg-21.htm

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MPEG 21

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Theoretical Problems in Metadata: Flat v. linked records

Flat record

All information about an item is held in a single record (e.g., a Dublin Core record), including information about related items

convenient for access and preservation

information is repeated -- maintenance problem

Linked record

Related information is held in separate records with a link from the item record

less convenient for access and preservation

information is stored once

Compare with normal forms in relational databases

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Representations of Dublin Core: XML (with qualifiers)

<title>Digital Libraries and the Problem of Purpose</title>

<creator>David M. Levy</creator>

<publisher>Corporation for National Research Initiatives</publisher>

<date date-type = "publication">January 2000</date>

<type resource-type = "work">article</type>

<identifier uri-type = "DOI">10.1045/january2000-levy</identifier>

<identifier uri-type = "URL">http://www.dlib.org/dlib/january00/01levy.html</identifier>

<language>English</language>

<rights>Copyright (c) David M. Levy</rights>to be continued

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Dublin Core with flat record extension

Continuation of D-Lib Magazine record

<relation rel-type = "InSerial">

<serial-name>D-Lib Magazine</serial-name>

<issn>1082-9873</issn>

<volume>6</volume>

<issue>1</issue>

</relation>

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Theoretical Problems in Metadata: Many Languages

See:

Thomas Baker, Languages for Dublin Core, D-Lib MagazineDecember 1998, http://www.dlib.org/dlib/december98/12baker.html