The generic product description resource is made up of schemas that reflect the different kinds of data that may be associated with a product. The application_context_schema allows for the description of the conditions under which a given instance of the generic product description resource was defined. The product_definition_schema supports the description of data that relates to a particular product. The product_property_definition_schema supports the description of the properties of this product, for example, its shape and material. The product_property_representation_schema specifies the ways in which a property of a product may be represented. The relationships between these schemas are shown in Figure 1.

• Application context: a product_definition is defined in at least one application context and may be used in zero, one, or many application contexts. A single application context may be used to define zero, one, or more product_definitions.
• Product property definition: a product_definition may have one or more property definitions associated with it;
• Property representation: each property definition may be represented in one or more ways. The only property that is expanded in this edition of this part is shape.

E.2.1 acyclic_object_relationship

The template described in this clause is used in various ISO 10303 integrated resources. It is a function that detects cyclic definitions.

The acyclic_object_relationship function determines whether the graph of instances of the entity data type object that contains relation as one of its links contains a cycle. This function may be used to evaluate either a object_relationship or any of its subtypes.

Let Z be a set of instances of the entity data type object. The initial content of Z is the content of the set provided by the parameter relatives. Let R be the instance of object referred to by the attribute relation.relating_object. The functions looks for the instances of specific_relation that refer to R through their attribute object_relationship.related_object. It adds to Z the set of instances of object that are referred to by these instances of specific_relation through their attribute object_relationship.relating_object.

The function then recursively applies the same search for each new element of Z until each branch of the graph has been fully explored or until a cycle has been detected. The function detects a cycle and returns FALSE if, at any stage of the search, an instance proposed for addition to Z already exists in Z. Otherwise, it returns TRUE.

NOTE 1   Calls to functions based on this template should be done as follows.

WR1: acyclic_object_relation (SELF, [SELF.related_object], '....' );

FUNCTION acyclic_object_relationship
	(relation		   : object_relationship;
	 relatives	 	   : SET [1:?] OF object;
	 specific_relation : STRING) : BOOLEAN;
		
  LOCAL
	x 			   : SET OF object_relationship;
  END_LOCAL;
		
  IF relation.relating_object IN relatives THEN
	RETURN (FALSE);
  END_IF; 			   -- IN is based in instance equality
	  
  x := QUERY (oor <* bag_to_set (USEDIN
  	   (relation.relating_object,
  	    'OBJECT_SCHEMA.' +
  	    'OBJECT_RELATIONSHIP.' +
  	    'RELATED_OBJECT')) |
  	     specific_relation IN TYPEOF (oor));
  REPEAT I := 1 TO HIINDEX(x); 			   -- pre-checked loop
    IF NOT acyclic_object_relationship
    	   (x[i],
    	    relatives + relation.relating_object,
    	    specific_relation) THEN
      RETURN(FALSE);
    END_IF;
  END_REPEAT;
	  
  RETURN(TRUE);
END_FUNCTION;
	

relation: (input) the candidate object_relationship to be checked.

NOTE 2   The instance of the object_relationship entity specified in the relation parameter of acyclic_object_relationship function is either an object_relationship entity or one of its subtypes.

relatives: (input) the set of instances of the entity data type object that defines the domain for the detection of cycles.

specific_relation: (input) the fully qualified entity name of the entity data type object_relationship or of one of its subtypes.

E.3.1 object_relationship

The template described in this clause is used in various ISO 10303 integrated resources. It supports the description of graphs of like objects.

An object_relationship relates two objects with a description of their relationship.

ENTITY object_relationship;
  name		  : label;
  description 	  : text;
  relating_object : object;
  related_object  : object;
END_ENTITY;
	

name: the label by which the object_relationship is known.

description: the text that characterizes the object_relationship.

relating_object: one of the instances of object that is a part of the relationship.

NOTE 1   The meaning of this attribute can be defined in the annotated EXPRESS schemas that use or specialize this entity, or in an agreement of common understanding between the partners sharing this information.

related_object: the other instance of object that is a part of the relationship. If one element of the relationship is dependent upon the other, this attribute shall be the dependent one.

NOTE 2   The meaning of this attribute can be defined in the annotated EXPRESS schemas that use or specialize this entity, or in an agreement of common understanding between the partners sharing this information.

In order to constrain the population of instances of the basic_attribute_schema, the following rule may be used in EXPRESS schemas that use or specialize the constructs of this part of ISO 10303. The rule attribute_x_not_allowed enforces the restriction that the attribute x of any instance of the entity data type entity_type not be present.

NOTE    Such a rule can only be specified in cases in which the referenced attribute is optional.

RULE  attribute_x_not_allowed FOR (entity_type) ;
WHERE
	  wr1: SIZEOF (QUERY (ent <* entity_type | EXISTS (ent.x))) = 0;
END_RULE;
	

The EXPRESS elements specified in the management_resource_schema are used to associate management type data with product data in specific application interpreted models. This clause describes the EXPRESS mechanism that is used to make these associations.

The ABSTRACT SUPERTYPE statement from the EXPRESS language is used in the management_resource_schema to define template structures that are used to associate management type data with product data in an application interpreted model.

The approval_assignment entity from the management_resource_schema defines a template structure that is used to associate approvals with product data.

ENTITY approval_assignment
  ABSTRACT SUPERTYPE;
   assigned_approval : approval;
  DERIVE
     role            : object_role := get_role (SELF);
WHERE
   WR1 : SIZEOF (USEDIN (SELF, 'BASIC_ATTRIBUTE_SCHEMA.' +
					 'ROLE_ASSOCIATION.ITEM_WITH_ROLE')) <= 1;
END_ENTITY; -- approval_assignment
	

These template structures are used in application interpreted models in which the management type data is to be associated with product data, in the following way:

• a SELECT type, and the necessary EXPRESS USE and REFERENCE statements, that defines the EXPRESS elements that are to have a particular kind of management type data associated with them is specified;
• an entity, and the necessary EXPRESS USE and REFERENCE statements, that is a SUBTYPE of the required template structure and that has an attribute that is of the type of the SELECT type is specified.

If approvals are assigned to drawing sheet revisions and drawing revisions, the following SELECT type would be defined:

TYPE approval_item = SELECT
     (drawing_sheet_revision,
      drawing_revision );
END_TYPE;
	

The following applied_approval_assignment entity could be used to associate approval with drawing sheet revisions and drawing revisions:

ENTITY applied_approval_assignment
    SUBTYPE OF (approval_assignment);
    item : approval_item;
END_ENTITY;
	

NOTE    In order to facilitate interoperability among application protocols, subtypes of the entity data type xxx_assignment are conventionally named applied_xxx_assignment in the application interpreted models.

In the management_resource_schema each abstract xxx_assignment entity has a role attribute. This attribute allows the characterization of the resource construct xxx with respect to the product data to which it will be assigned.

For example, in particular instances of the entity data type applied_contract_assignment, the derived attribute role can refer to instances of the entity data type object_role with name 'does not apply', or 'is the binding agreement for the production of', in order to characterize the role of a contract with respect to a particular product.

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