Definition of Attribute
Definition Last Updated 17-Dec-2015 12:51
An attribute is a state comprising one or more characteristics, i.e. observables1Though not necessarily under all circumstances, it must be observable in principle. or tags, that has been attributed2i.e. given to, from the latin attribuere (to give to) formed by composing ad (to) and tribuere (to give), typically implying intrinsicality or innateness; the appropriate verb for connecting characteristics to places and times in the absence of identified entities would be allocate, ad (to) and locare (to place). to a specific entity (i.e. some thing that has been identified3See the article on Entity for information on the identification of entities.). If the characteristic is named4Here name means a simple designator, such as mass; the characteristic whose name is mass could also be described as, “the intrinsic constant of proportionality between force and acceleration”. In general, anything that designates may be called a name, but some things are more naturally names than others., it may also be referred to as a property.
Distinct entities may have attributes bearing the same name: the assignment of characteristics to things is achieved via the specification of observations; this is discussed in detail in the main article.
[Attribute] is [state] attributed to [entity]
[State] attributed to [entity] is [attribute]
[Entity] has [state] as [attribute]
Article Last Updated 17-Dec-2015 12:51
Note that although entities may have attributes, entities must first be identified before anything can be attributed to them. Identification is performed by the application of rules (containing criteria that constitute a reference description or standard for the identification of something) to the values of observables. Attributes are therefore ontologically secondary to observables – they are only attributes because they belong to an entity.
Thus, when modelling, there is no fundamental type attribute: an attribute is just a set of characteristics that has been associated with an entity. An “attribute” that is not related to an entity5And so, by definition, not really an attribute. is just the concept of a characteristic that something might – or might not – actually have.
Note that characteristic in the definition is a noun; whilst a particular value of an attribute might be characteristic of (adjective) something (e.g. Colour: green, characteristic of plants), a characteristic defines the nature of the observation and its measurement or assessment.
Measurements are typically absolute and objective (though subject to errors, systematic and random) whereas assessments such as “good” or “bad”, “high” or “low” are typically subjective or relative, and prone to their own particular kinds of errors. Attributes such as “good”, “high”, etc. may be considered secondary or derived attributes as they are typically derived by relating some measured characteristic to one or more reference values and therefore have implied criteria.
It is also important to be clear about the distinction between parts of an entity and characteristics of an entity.
Parts vs Attributes
Section Last Updated 17-Dec-2015 12:51
An animal may have legs, a car may have wheels; are legs and wheels attributes or ( ) parts?
Firstly, we can say that whilst legs and wheels can be observed, they are not observables: observables are intrinsic characteristics such as length or mass, whose values are independent of any entity identification. However, in order to be able to say, “There’s a leg,” one must have performed an identification whose result is “leg”. Therefore, since one cannot refer to (point at) specific legs or wheels without having previously circumscribed and identified them as entities, they are not independent of identification and so cannot be observables as defined.
Could legs or wheels be tags, the only other kind of characteristic, instead?
Again the answer is no. A tag says something about an entity; what does a leg say about an animal it belongs to other than, “I am the leg of…”, which is clearly a relationship – and relationships require the identification of entities. For “I am the leg of…” to make sense, the leg has to be an identifiable entity, and if it’s an identifiable entity then the most natural conclusion is that it’s a part.
Thus, anything that can be identified as an entity within another entity is a part and not an attribute of the latter.
That having been said, the number of legs possessed by an animal is a characteristic: legs can be counted and thus number of legs is an observable.
Note also that an attribute may itself be compound: the (physical) size of an object might be specified in terms of length, width and height and these might be individual attributes or they might be grouped together as a single size attribute with slots for the three individual values. When an attribute has parts, the parts are not attributes of the attribute, they are just parts of it – but they are attributes of the object, i.e. any part of a compound attribute of an entity is also an attribute of that entity.
Discussion of how one distinguishes an intrinsic, dependent part (such as my liver) from an independent part (the marble I swallowed for a dare) is deferred to another time.
Physical objects are typically coloured, i.e. have an attribute called “Colour”. In giving a value for the colour of something we might use simple colour words (red, purple, orange), or a formal colour-space measurement in terms of the brightness of red, green and blue colour components (RGB system). Whether we wish to use words or RGB pixel values only affects the data type of the attribute.
Notes [ + ]
|1.||⬆||Though not necessarily under all circumstances, it must be observable in principle.|
|2.||⬆||i.e. given to, from the latin attribuere (to give to) formed by composing ad (to) and tribuere (to give), typically implying intrinsicality or innateness; the appropriate verb for connecting characteristics to places and times in the absence of identified entities would be allocate, ad (to) and locare (to place).|
|3.||⬆||See the article on Entity for information on the identification of entities.|
|4.||⬆||Here name means a simple designator, such as mass; the characteristic whose name is mass could also be described as, “the intrinsic constant of proportionality between force and acceleration”. In general, anything that designates may be called a name, but some things are more naturally names than others.|
|5.||⬆||And so, by definition, not really an attribute.|