Issue 431: make methodology clear
Taking into account the discussion in the crm-sig list about Place vs. SpaceTimeVolume, Martin proposes to add in the CRM, in the section Terminology, definition of "Class", to add an adequate variant of
"It is per definitionem wrong for all CRM concept to argue with the meaning of the label. Labels can only be wrong wrt to the scope note. Per definitionem they do not constitute definitions."
In the 45th joint meeting of the CIDOC CRM SIG and SO/TC46/SC4/WG9; 38th FRBR – CIDOC CRM Harmonization meeting, the sig sided with adding a clause conveying the meaning that the label of a class is not its definition –along the lines of that proposed by MD: “It is per definitionem wrong for all CRM concepts to argue with the meaning of the label. Labels can only be wrong with respect to the scope note. Per definitionem they do not constitute definitions.”
HW: MD is to update the definition of class in the Terminology section of the CRM, by adding the aforementioned clause.
Heraklion, October 2019
Posted by Martin on 16/1/2020
Here my proposal, in italics the additions, at three places:
A class is a category of items that share one or more common traits serving as criteria to identify the items belonging to the class. These properties need not be explicitly formulated in logical terms, but may be described in a text (here called a scope note) that refers to a common conceptualisation of domain experts. The sum of these traits is called the intension of the class and constitutes its definition. In the CRM, a class is identified by an alphanumeric code and a name, for mnemonic reasons, which should not be regarded as definition. A class may be the domain or range of none, one or more properties formally defined in a model. The formally defined properties need not be part of the intension of their domains or ranges: such properties are optional. An item that belongs to a class is called an instance of this class. A class is associated with an open set of real life instances, known as the extension of the class. Here “open” is used in the sense that it is generally beyond our capabilities to know all instances of a class in the world and indeed that the future may bring new instances about at any time (Open World). Therefore a class cannot be defined by enumerating its instances. A class plays a role analogous to a grammatical noun, and can be completely defined without reference to any other construct (unlike properties, which must have an unambiguously defined domain and range). In some contexts, the terms individual class, entity or node are used synonymously with class.
E21 Person is a class. To be a person may actually be determined by DNA characteristics, but we all know what a person is. The scope note of E21 Person clarifies the exact sense of this class in contrast to other possible meanings of ‘person’ in natural languages. A person may have the property of being a member of a Group, but it is not necessary to be member of a Group in order to be a Person. We shall never know all persons of the past. There will be more persons in the future.
A scope note is a textual description of the intension of a class or property.
Scope notes are not formal modelling constructs, but are provided to help explain the intended meaning and application of the CIDOC CRM’s classes and properties. Basically, they refer to a conceptualisation common to domain experts and disambiguate between different possible interpretations. They constitute approximate definitions. The name of a class is a mnemonic help for the content of the scope note and not part of the definition. Illustrative example instances of classes and properties are also regularly provided in the scope notes for explanatory purposes.
The following naming conventions have been applied throughout the CIDOC CRM:
· Classes are identified by numbers preceded by the letter “E” (historically classes were sometimes referred to as “Entities”), and are named using noun phrases (nominal groups) using title case (initial capitals) as mnemonics for the content of the scope note. For example, E63 Beginning of Existence.
· Properties are identified by numbers preceded by the letter “P,” and are named in both directions using verbal phrases in lower case as mnemonics for the content of the scope note. Properties with the character of states are named in the present tense, such as “has type”, whereas properties related to events are named in past tense, such as “carried out.” For example, P126 employed (was employed in).
Posted by Carlo on 17/1/2020
Works very well for me, I’d sharpen it a bit by replacing
"A class is associated with an open set of real life instances, known as the extension of the class”.
“In any interpretation, or possible world, a class is associated with a set of real life individuals, known as the extension of the class in that interpretation. The sum of the extensions over all interpretations equals to the intension of the class."
Posted by Martin on 17/1/2020