Attributes and Values Describing Entities

Metadata At the most basic level, metadata is just another term for description, or information about an entity. In creating a descriptive schema, you are creating a template for assigning metadata to a particular group of items in a structured way.

Types of metadata Gilliland defines five types of metadata: Administrative. Descriptive. Preservation. Technical. Use.

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.

Examples of attribute/value pairs For Web pages, some attribute/value pairs might be: Attribute Value Address A valid URL Date modified A date in MM/DD/YYYY format Links to other pages A list of valid URLs

More examples of attribute/value pairs For restaurants to which I might consider taking visitors to Austin, potential attribute/value pairs might be: Attribute Value Sense of place A scale from 1-10 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 Thinking ahead to Wilson’s two kinds of power, the Web site attributes from the previous slide are very much descriptive. They help me to specify an existing item that I know about. But attributes, as we have seen, can also be optimized for a specific context. of course, while these exploitative attributes might be very useful, they are also limited to a very particular situation and may be quite difficult to define in a way that can be easily operationalized, in other words, where I can explain to other potential contributors of resources and metadata what the attributes mean and how the values should be assigned. So in many cases we likely want attributes that represent some middle ground between these two examples. However, don’t dismiss the potential usefulness of “subjective” attributes and values like this. This is where things get interesting. This is where I might actually learn something that I didn’t know before, or at least get an idea of what other people think, even if I decide that I don’t agree. The challenge with these is to define the value space precisely enough that people using the schema--and by that I mean people adding new instances, or new descriptions, as well as people reading the descriptions--can get a reasonable idea of what I mean when I say something like “grease quotient” and that these values can be used to consistently and coherently differentiate between the entities described.

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). .

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.

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.

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.

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.

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.

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"

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”

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.