Quality

Category

Aspect

Provides identity

yes

Identity principle

single

Rigidity

rigid

Dependency

mandatory

Allowed supertypes

Category, Mixin

Allowed subtypes

Subkind, Role, Phase

Forbidden associations

ComponentOf, SubCollectionOf, MemberOf, SubQuantityOf, Derivation

Abstract

True

Definition

A «Quality» is a particular type of intrinsic property which has a structured value. Qualities are things that are existentially dependent on the things they characterize, called their bearers. Types stereotyped as «Quality» are also rigid. OntoUML differentiates between three types of qualities:

• Perceivable, which capture qualities that could be measured by an agent with the appropriate instrument, like weight, height, color and speed.

• Non-Perceivable, which represent properties which cannot be directly measured by an instrument, like currency.

• Nominal, which are used to make reference to an individual, like one’s name, a book’s ISBN or a credit card number.

Notice some examples of qualities in the next figure:

You can define different types of geometrical structures for a quality value using dimensions and domains. Here is an example:

Constraints

C1: A «Quality» must always be connected, through a «Characterization» to another type.

C2: The multiplicity of the characterized end (opposite to the quality) must be exactly one. Therefore, the following examples are forbidden.

C3: Qualtities cannot have as ancestors the following types: «Kind», «Quantity», «Collective», «Subkind», «Role», «RoleMixin», «Phase», «Relator», «Mode».

C4: Qualtities cannot have as descendants the following types: «Kind», «Quantity», «Collective», «RoleMixin», «Category», «Mixin», «Relator», «Mode».

Common questions

Q1: Can I represent the property “height” as an attribute instead of a «Quality»?

A1: Yes. The decision to represent attributes or qualities is entirely up to you. It is useful to represent properties as qualities when you want to define different escales for the same characteristic. For instance, if you want to model that a Person has a “height” property, which can be measured in meters or centimeters you should explicitly represent the Height quality.

Examples

No examples yet…