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EDCS Reference Manual
EDCS Structure |
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Every concept has a definition, two ways to denote that concept (a label, a code), and ties to concepts in other documents (standards, specifications, dictionaries, publications).
The definition field of an EDCS Dictionary Entry is a precise statement of the nature, properties, scope or essential qualities of a concept embodied in the entry. Definitions are complete and concise, and may include the name or names for the concept as part of the definition.
The label field of an EDCS Dictionary Entry is a compact and human-readable designator that is used to denote a concept. Labels may include the name or names for the concept. Labels:
The code field of an EDCS Dictionary Entry is a compact, and not necessarily human-readable, designator that is used to denote a concept. Codes:
There is a one-to-one relationship between labels and codes in the same EDCS Dictionary. Therefore, a label and a code may be used interchangeably to denote the same concept.
Concepts in two documents (the EDCS and some external document) may be related in several different ways. Reference types, references, and supplemental references establish the relationship between an EDCS concept and an external concept.
To improve unambiguous communication across disparate domains, the goal is to bring together (consistently) concepts that are seen as "authoritative" in those domains. Typing references helps identify the degree to which an EDCS concept is viewed as "authoritative" in another community. It also may serve as a starting point for developing mappings from the specialized languages of communities to the cross-community language of the EDCS. Two types of reference (normative and informative) are insufficient to capture all of the possible relationships between the EDCS and another document. In the following, a specification is a document that meets the requirements to be normatively referenced by the EDCS, and the owner of such a specification is the organization responsible for maintaining the specification.
Prescriptive reference (PR): The concept in the EDCS is the same concept as defined in an external specification. The definition of the concept in EDCS may be different from the definition in the specification because of modifications to:
Authoritative reference (AR): The concept in the EDCS prescriptively references a concept from an external specification, and an agreement has been established between the owner of the EDCS and the owner of that specification to ensure that the concept authoritatively referenced is not changed without the agreement of the owner of the EDCS. In this case, a citation is provided in the references field.
Informative reference (IR): The concept from the EDCS is related to, or derived from, concepts in one or more external documents. In this case, one or more citations are provided in the references field.
Non-referenced (NR): No satisfactory prescriptive, authoritative, dictionary or informative reference is available in another document for re-use as a concept in the EDCS. The meaning of the definition of the concept is determined by using the appropriate dictionary definitions of the words comprising the definition, considering the context in which each word is used. In this case, no citation is provided in the references field.
Concepts may be used within the definition of other concepts. This creates a web of explicitly inter-related concepts, reduces the complexity of individual definitions, and ensures that concepts in, and across, dictionaries "fit together".
If an EC is used in the definition of another concept, this use is represented in the definition by placing the label for that EC in single angle brackets (< >) in the definition.
If an EA is used in the definition of another concept, this use is represented in the definition by placing the label for that EA in double angle brackets (<< >>) in the definition.
If an EE is used in the definition of another EE for the same enumerated EA, this use is represented in the definition by placing the label for that EE in triple angle brackets (<<< >>>) in the definition.
Classifications are typings-of-objects (in the EC Dictionary); attributes are states-of-objects (in the EA Dictionary). Attributes are, in effect, measures. Measures are typed in order to define the value storage mechanism being used. Attributes have one of the following value-types assigned:
Real-, integer-, and count-typed attributes may be either a single value or an interval (value-pair). Real-typed attributes have units of measure, which are captured in the EU Dictionary.
Measures may be missing, withheld, many-valued (for a partitioned range), etc. These value characteristcs are captured using concepts in the EV Dictionary.
While some measures are continuously valued (real, integer, count), others are discretely valued (e.g., null, boolean, enumeration). While the discrete values of null and boolean can be pre-defined, the discrete values of enumeration depend on the attribute concept -- hence attributes of value-type enumeration must declare their value domain (e.g., attribute colour has the value domain of {red, orange, yellow, green, ...} ). Concepts in the value domain of a measure (attribute) have their own EE Dictionary, and all of the mechanisms applied to classifications (which are typings-of-objects, as opposed to typings-of-discrete-values-of-measures) are applied to attribute enumerants.
Units characterize the measurement of quantities. Some quantities may have more than one appropriate unit-of-measure. Unit equivalence classes (in the EQ Dictionary) identify units that are comparable, and therefore values characterized by those different units of measure can be interconverted (e.g., foot-to / from-metre). A functional interface is defined, and implemented, to support such value conversions. While most units are compliant with the SI (Système International), some predate the SI. While they are supported, they are also deprecated (e.g., statute mile, hectare, knot, rad). Attribute values may be scaled in order to better support a community of interest (e.g., kilometres, hectopascal, milligrams). The ES Dictionary includes such concepts.
Concepts can be organized into groups (in the EG Dictionary) sharing a common "scope of application" or "theme" (e.g., living organisms, vehicles, space, land transportation). Concepts can be relevant to multiple groups (e.g., the U.S. Space Shuttle is relevant to both the vehicles and space groups). Classifications and attributes can be (multiply) grouped. Groups aid in searching the EDCS to find concepts of relevance to a coding task. Membership in a group does not affect/change the concept.
Groups are members of organizational schema (in the EO Dictionary), such that every classification or attribute concept is required to be a member of at least one group in that schema. This ensures that there are no "holes" in the coverage of the groups comprising a schema. Many schema (and their groups) can be defined; each from the perspective of a community-of-interest. Only one such schema is currently defined, general, however more can be easily added.
In order to support continuous evolution and growth of the EDCS, a low-overhead process of registration has been defined, allowing for the timely addition of new concepts to the EDCS. Additionally, a slower, measured process of deprecation has been defined for removing out-dated or inappropriate concepts from the EDCS.
In order to support the specification of rational subsets of the EDCS for use within a community, and constraints on the use of specific combinations of concepts from the EDCS, a profile mechanism has been defined. The base profile includes all concepts from all EDCS Dictionaries, and includes no constraints. Additional profiles may be defined through the registration process.
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