Attributes and Values
Describing Entities
Attributes and values
Attributes—also known as characteristics,
properties, or elements—are the categories we
use to describe a specific kind of entity more
precisely.
Values are a way to describe the possible
contents of an attribute.
INF 384C, Spring 2009
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Examples of attribute/value pairs
For Web pages, some attribute/value pairs might
be:
Attribute
Value
Address
Date modified
Links to other pages
A valid URL
A date in MM/DD/YYYY format
A list of valid URLs
INF 384C, Spring 2009
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More examples of attribute/value pairs
For restaurants that I to which I might consider taking my
sister when she visits Austin over spring break, potential
attribute/value pairs might be:
Attribute
Value
A scale to represent the restaurant’s
uniqueness as an Austin or Texas experience
Grease quotient
The number of margaritas required to cut
through the richness of the food
Ease of transport
A percentage that represents the likelihood
that I can get us there, park, and get us
home without harming us, others, or property
Sense of place
INF 384C, Spring 2009
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Schemas, or attribute sets
A schema is a set of attributes and associated value
parameters designed to describe a particular type of
entity.
Schemas may be encoded in a particular syntax for
manipulation by people or computers.
Schemas may also be associated with rules for creating
records (that is, assigning attributes and values to
specific resources).
INF 384C, Spring 2009
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Dublin Core: a schema
The Dublin Core is a metadata schema for describing
(primarily) information resources. It includes a set of
elements (attributes) and associated value parameters.
A goal of Dublin Core is to provide a simple set of
standard attributes that apply to most documents. By
making it easy to comply with Dublin Core standards,
interoperability of metadata between different
collections may be facilitated.
INF 384C, Spring 2009
Slide 6
Dublin Core elements (attributes)
“Simple” Dublin Core includes 15 basic elements. When assigning metadata to
resources, all elements are optional and repeatable.
In “qualified” Dublin Core, there are 3 additional elements, and some elements
can be refined. For example, Abstract is a refinement of the Dublin Core
Description element, making the element more specific.
To support the interoperability goal, metadata authors must assume that
qualifiers may be “dumbed down” if systems don’t support them. That is, an
Abstract element may be “dumbed down” back to the Description element.
INF 384C, Spring 2009
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Dublin Core values
The values for Dublin Core elements may come from controlled
vocabularies. For some elements, potential vocabulary encoding
schemes are identified (such as the “DCMIType vocabulary” for
the Type element).
For example, the creator of metadata for a particular collection
might specify that values for the Subject element must be selected
from the Library of Congress Subject Headings (LCSH) and not
by entering free keywords.
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Audience for Dublin Core records
The “audience” for Dublin Core metadata may be a
person, or it may be a computer, using the metadata to
facilitate search or do other processing.
INF 384C, Spring 2009
Slide 9
Dublin Core element descriptions
Hillman’s usage guide provides a label, text description,
usage guidelines, and examples for each element.
You may find this format useful in thinking about how
to create similar descriptions and guidelines for your
schema assignment.
INF 384C, Spring 2009
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Title element
Label: Title
Element Description: The name given to the resource. Typically, a Title will be a name
by which the resource is formally known.
Guidelines for creation of content:
If in doubt about what constitutes the title, repeat the Title element and include the
variants in second and subsequent Title iterations. If the item is in HTML, view the
source document and make sure that the title identified in the title header (if any) is
also included as a Title.
Examples:
Title="A Pilot's Guide to Aircraft Insurance"
Title="The Sound of Music"
INF 384C, Spring 2009
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Type element
Label: Resource Type
Element Description: The nature or genre of the content of the resource. 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 DCMIType vocabulary ). To describe the physical or digital
manifestation of the resource, use the FORMAT element.
Guidelines for content creation:
If the resource is composed of multiple mixed types then multiple or repeated Type elements should be used to
describe the main components. Because different communities or domains are expected to use a variety of type
vocabularies, best practice to ensure interoperability is to include at least one general type term from the
DCMIType vocabulary in addition to the domain specific type term(s), in separate Type element iterations.
Examples:
Type="Image"
Type="Sound"
Type="Text"
Type="simulation”
INF 384C, Spring 2009
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Dublin Core power?
Some Dublin Core elements may not be that easy to
describe after all, but in its goal of facilitating
interoperability, DC focuses on descriptive power, not
exploitative.
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Summary
• A schema is a set of attributes to describe a defined group of
entities, along with associated value parameters and usage
guidelines. We use the schema to produce metadata records that
describe specific objects.
• Dublin Core is a schema for describing information resources in
a way that facilitates interoperability between metadata systems.
•
• Defining attributes in a way that makes it clear how to create
records with them can be quite challenging, even for seemingly
basic descriptive attributes.
INF 384C, Spring 2009
Slide 14