3.4. Data Description Section of the DRM Abstract Model    (3X0Z)

The Data Description section of the DRM abstract model is shown in figure 3-1. It depicts the concepts that comprise the Data Description standardization area and the relationships between them. Concepts are expressed as boxes, while relationships are expressed as arrows. A concept group, an aggregation of related concepts, is also expressed in this section of the DRM abstract model as the Data Schema concept group.    (3X10)

NOTE: The “Document” concept below represents an example of one kind of data object.    (3X11)

http://colab.cim3.net/file/work/das/DRM_2.0/Figure_3_1.JPG    (3YP9)

The following are definitions for each of the concepts and relationships within the figure shown above. Conventions used are:    (3X12)

Data Schema: A representation of metadata, often in the form of data artifacts such as logical data models or conceptual data models. The Data Schema concept group is comprised of those concepts pertaining to the representation of structured data. A Data Schema provides a means to provision data sharing services that is independent of the values of the data in the data resource that it describes.    (3X17)

Entity: An abstraction for a person, place, object, event, or concept described (or characterized) by common Attributes. For example, “Person” and “Agency” are Entities. An instance of an Entity represents one particular occurrence of the Entity, such as a specific person or a specific agency.    (3X1A)

Data Type: A constraint on the type of physical representation that an instance of an Attribute may hold (e.g. "string" or "integer").    (3X1D)

Attribute:' A characteristic of an Entity whose value may be used to help distinguish one instance of an Entity from other instances of the same Entity. For example, an Attribute of a “Person” Entity may be “Social Security Number (SSN)”. An SSN is used to distinguish one person (i.e. one instance of a “Person” Entity) from another.    (3X1F)

Relationship: Describes the relationship [6] between two Entities.    (3X1H)

Digital Data Resource: A digital container of information, typically known as a file. A Digital Data Resource may be one of three specific types of data resources, each corresponding to one of the three types of data described earlier, and each described below (see “Structured Data Resource”, “Semi-Structured Data Resource”, and “Unstructured Data Resource”). It will be a container for the metadata about the data resource.    (3X1J)

Structured Data Resource: A Digital Data Resource containing structured data. This data can be accessed in a uniform manner, independent of data values, once the Data Schema is known.    (3X1M)

Semi-Structured Data Resource: A Digital Data Resource containing semi-structured data. This will generally consist in part of structured data and in part of unstructured data.    (3X1O)

Unstructured Data Resource: A Digital Data Resource containing unstructured data. Unstructured data is collection of data values that are likely to be processed only by specialized application programs.    (3X1Q)

Document: A file containing Unstructured and/or Semi-Structured Data Resources.    (3X1S)

NOTE: While a Document can contain structured data, it normally has explanatory material included, which would cause it to therefore be considered semi-structured. It is for this reason that there is no “contains” relationship from Document to Structured Data Resource. It is very important to separate Documents from Structured Data Resources because they are processed very differently. The difference between a Document and a Digital Data Resource, therefore, is that a Digital Data Resource can contained structured data.    (3X1V)

[6] It should be noted that the term "relationship" is used in two ways here. The concept named "Relationship" participates in relationships with other concepts in the abstract model, and also defines the relationship between entities when it is applied to a specific scenario.    (3YP7)