Step Three: Description Set Development

Steps 3 and 4a in the DCAP process are closely related. Step 3 carefully and fully documents in human-readable form the intended Description Set (or general graph shape) of the set of related entities in the Domain Model. For example, a "description set" for a specific credential might, at a minimum, include resource descriptions for:

Step 3: Description Set Development

Thus, at the close of Step 3, the Credential Engine Technical Advisory Committee and the Credential Engine Technical Team will have created human-readable documentation for all classes and properties of which the CT description language (CT-DL) is comprised. In addition, an RDF schema is created using W3C's Resource Description Framework Schema (RDFS) for all properties and classes not borrowed from other namespaces such as

In addition, all descriptive datatype properties derived from the use cases and Credential Engine Technical Advisory Committee analysis are fully described. These class/property descriptions are also represented in table form following a well prescribed set of property/class attributes.

In Step 4a, the human-readable tables describing the classes and properties of the "description set" are transformed into one or more description set profiles by: (1) recasting the constrained Description Set into a machine-readable form using a Constraint Language; and (2) applying constraints on properties and classes to meet particular needs—e.g., the need for "full" and "thin" applications seen in Figure 4 of Step 2.

Selecting and Creating "Terms"—Properties & Classes:

During Steps 1-2, preliminary determinations are made regarding: (a) the types of entities that must be described to support the CT use cases; and (b) the kinds of statements that the metadata must make about each of those entities. Here in Step 3, the Credential Engine Technical Advisory Committee and the Credential Engine Technical Team determine whether the entities and the statements called for in the use cases and Credential Engine domain model already exist in publicly available RDF schemas. To support interoperability and broad adoption, the Committee should advise the reuse of publicly existing, and well recognized, classes and properties as opposed to unnecessary 'coining' of new terms. The Committee's initial focus should be the suitability of resource types and their accompanying properties with the goal of the CT-DL being chiefly comprised of extensions.

Documenting Table Properties:

Each resource class and each of their associated properties are documented in the Description Set with an individual table describing their attributes. The following table contains rows defining each attribute to be described.

Class or Property


Class (C) or Property (P)

Attribute Description



The Uniform Resource Identifier used to uniquely name/identify the term.



The human-readable label assigned to the term.



A statement that represents the concept and essential nature of the term.



Additional information about the term or its application.

Type of Term


The type of term—Class or Property—identified by RDF/RDFS URI.

Subproperty Of


The URI of a Property of which the described term is a Subproperty.

Has Range/Range Includes


The URI(s) of the Class(es) that are either inferred to be used (has range) or that are typically used (range includes) as objects of the property.

Has Domain/Domain Includes


The URI of the Class that is either inferred to be used (has domain) or that is typically used (domain includes) as subject of the property.

Subclass Of


The URI of a Class of which the described term is a Subclass.

At the conclusion of this part of the Step 3, each property and each resource type or class will have been explicitly defined in human-readable form.

Creating the RDF Schema

For properties and classes in the tables that are being newly coined by CTI, an RDF schema defining those properties and classes will be created using constructs from W3C's RDF Schema 1.1 data-modeling vocabulary for RDF data.

Credential Engine Namespace Policy for Classes & Properties

During Step 3, there will be properties—and likely some classes—that the Credential Engine project will have to formally define in an RDF schema because there are no suitable existing terms. Among those to be defined will be the properties and classes for a proposed extension to Since the means in RDF of identifying properties and classes is by URI, temporary URI conventions must be adopted until a determination of the permanent namespaces. Use of a temporary, experimental namespaces also precludes the premature use of the properties and classes in production systems during development and public vetting stages.

The following namespace designation shall be used during development ("ex"=experimental):

  1. Experimental namespace for newly CTI-coined properties and classes:
  1. Experimental namespace for CTI-developed controlled vocabularies (enumerations of "values")