4 Classification schema

REFERENCE FROM group_schema    --  ISO 10303-41
  (group);



REFERENCE FROM management_resources_schema    --  ISO 10303-41
  (classification_assignment);
(*



NOTE 1   The schemas referenced above are specified in the following part of ISO 10303:

group_schema	ISO 10303-41
management_resources_schema	ISO 10303-41

NOTE 2   See Annex D for a graphical representation of this schema.

4.1 Introduction

4.2 Fundamental concepts and assumptions

For many different entity types defined within ISO 10303, an instance may stand for a class or set of things. The fact that an instance stands for a class or set of things can be made explicit by creating a compound instance of:

• the entity type class defined in this part of ISO 10303, and
• another entity type defined in ISO 10303.

Members can be specified for an instance of the entity type class. An instance of the entity type class can be involved in set theory relationships, such as union or intersection, with other instances of the entity type class.

NOTE    Instances of the entity types product, product_definition_formation and product_definition in ISO 10303-41 can be classes. In order to allow set theory relationships for these classes, an application protocol or application module can define a subtype of:

• product_definition_formation (from ISO 10303-41);
• class (from this part of ISO 10303).

EXAMPLE 1   Pump model 'XYZ_123' is a product_definition_formation and a class. This class is a class_by_extension.

EXAMPLE 2   The set of pumps enumerated in maintenance contract '98/1234' is a class. This class is a class_by_intension.

EXAMPLE 3   The relationship between individual pump 'X/85/4567' and pump model 'XYZ_123', that indicates the model of the pump, is a classification.

EXAMPLE 4   The relationship between individual pump 'X/85/4567' and the set of pumps enumerated in maintenance contract '98/1234', that indicates it is one of the set, is a classification. The complete set of pumps covered by the contract can be defined by an instance of the entity type complete_membership.

EXAMPLE 5   The set of pumps that are both within maintenance contract '98/1234' and of pump model 'XYZ_123' can be defined by the set theory relationship intersection.

4.3 classification_schema type definitions

4.3.1 classification_select   

NOTE  This empty extensible select requires extension in a further schema to ensure that entities that refer to it have at least one valid instantiation.

EXPRESS specification:

*)
TYPE classification_select = EXTENSIBLE SELECT;
END_TYPE;
(*

4.3.2 complete_membership_select   

NOTE  This empty extensible select requires extension in a further schema to ensure that entities that refer to it have at least one valid instantiation.

EXPRESS specification:

*)
TYPE complete_membership_select = EXTENSIBLE SELECT;
END_TYPE;
(*

4.4 classification_schema entity definitions

4.4.1 class   

A class is a type of group that is a set.

NOTE 1   The term 'set' is defined in clause 3.3. In this part of ISO 10303, 'set' and 'class' are synonyms.

NOTE 2   The meaning of this entity is identical to:

• the entity class defined in ISO 10303-214; and
• the entity class defined in ISO 15926-2.

NOTE 3   A class can consist of all things with a particular set of properties. Hence information about the consequences of possessing the set of properties can be assigned to the class. If a thing is classified as being a member of such a class, then a set of properties possessed by the thing can be deduced.

NOTE 4   This entity may be instantiated as a compound instance involving another entity from ISO 10303.

NOTE 5   The distinction between a class_by_extension and a class_by_intension can be imprecise. For example, the set of items produced by a particular production run could be regarded as either. The entity type class is not specified as abstract, so an application protocol or application module can decide to ignore the distinction.

EXPRESS specification:

*)
ENTITY class
  SUBTYPE OF (group);
END_ENTITY;
(*

4.4.2 class_by_extension   

EXPRESS specification:

*)
ENTITY class_by_extension
  SUBTYPE OF (class);
END_ENTITY;
(*

4.4.3 class_by_intension   

EXPRESS specification:

*)
ENTITY class_by_intension
  SUBTYPE OF (class);
END_ENTITY;
(*

4.4.4 classification   

A classification is a type of classification_assignment that is a relationship between

• set S and
• thing x,

that indicates thing x is a member of set S.

NOTE    The meaning of this entity is identical to the entity classification defined in ISO 15926-2.

EXPRESS specification:

*)
ENTITY classification
  SUBTYPE OF (classification_assignment);
  classified : classification_select;
DERIVE
  classifier : class := SELF\classification_assignment.assigned_class;
END_ENTITY;
(*

Attribute definitions:

classified: the member of the classifier.

classifier: the class that has the classified as a member.

4.4.5 complete_membership   

A complete_membership is a type of classification_assignment that is a relationship between

• set S and
• enumerated things x_i,

that indicates set S contains each of the things x_i and nothing else.

EXPRESS specification:

*)
ENTITY complete_membership
  SUBTYPE OF (classification_assignment);
DERIVE
  containing_set : class := SELF\classification_assignment.assigned_class;
END_ENTITY;
(*

Attribute definitions:

containing_set: the class that contains the members and nothing else.

4.4.6 complete_membership_of_empty_set   

EXPRESS specification:

*)
ENTITY complete_membership_of_empty_set
  SUBTYPE OF (complete_membership);
END_ENTITY;
(*

4.4.7 complete_membership_of_non_empty_set   

EXPRESS specification:

*)
ENTITY complete_membership_of_non_empty_set
  SUBTYPE OF (complete_membership);
  members : SET[1:?] OF complete_membership_select;
END_ENTITY;
(*

Attribute definitions:

members: the elements of the containing_set.

4.5 classification_schema subtype constraint definition

4.5.1 classification_or_complete_membership

EXPRESS specification:

*)
SUBTYPE_CONSTRAINT classification_or_complete_membership FOR classification_assignment;
  ONEOF (classification,
         complete_membership);
END_SUBTYPE_CONSTRAINT;
(*

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