representing_value_w

Template:— representing_value_w_tolerances (rep_val_tol)

Date: 2008/03/10 09:26:28
Revision: 1.25

Cover Contents Description Model diags.Input params.Ref. params.Instantiation path Instance diags.Characterizations Issues

This section specifies the template representing_value_w_tolerances.

NOTE An explanation of a template and the associated instantiation path is provided in the Template overview section.

Description

This template describes how to represent tolerances for any associated a property value.

This can be defined as the upper and lower tolerance limits associated with a particular value and unit.

EXAMPLE The design weight (property) of an item is declared as 35 kilograms and the tolerance associated with that value may allow the weight to increase (+) 0.5 kg, (e.g. to 35.5kg) or to decrease (-) 4.0kg, (e.g. to 31kg).

NOTE The upper and lower values are taken to equate to the traditional +/- (plus and minus) engineering tolerance definition that may be associated with a particular value (and unit). Hence the 'lower' limit should always be negative.

Model diagrams

The EXPRESS-G diagram in Figure 1 shows the templates and EXPRESS entities that are required to represent the template "representing_value_w_tolerances". The text highlighted in blue shows the template parameters.

Figure 1 — An EXPRESS-G representation of the Information model for representing_value_w_tolerances

The graphic for the template to be used in other EXPRESS-G diagrams is shown in Figure 2 below.

Figure 2 — The graphical representation of representing_value_w_tolerances template

Input parameters

The following input parameters are defined for this template:

value (Type= 'TYPE (any_number_value)' )

The value of the property. The datatype is always 'any_number_value' and should not be registered together with the value, i.e. enter the value as a number, without datatype.

upper_limit (Default=0,Type='REAL')

The tolerance upper limit.

lower_limit (Default=0,Type='REAL')

The lower tolerance limit of the property value. This value should always be negative as upper_limit and lower_limit represent offsets from value, specifying a range of values defined as [value+lower_limit, value+upper_limit].

unit (Type='CLASS')

The class name of the unit in which the value is expressed.

The following classes and their sub-classes can be used:

classifications: "Unit" (urn:plcs:rdl:std:Unit)

unit_ecl_id (Default=urn:plcs:rdl:std,Type='URN')

The identifier of the External_class_library storing the definition of the class referenced by the parameter @unit.

si_unit (Type='BOOLEAN')

Value should be set to true if the unit is a SI base unit defined by ISO, i.e. kilogram (kg) for Mass, second (s) for Time, metre (m) for Displacement, ampere (A) for Electrical current, kelvin (K) for Temperature, mole (mol) for Amount of substance, and candela (cd) for Luminous intensity. If this is not the case it should be set to false.
Note that the representation of true and false depends on exchange format. In Part 21 (a STEP file) true is represented by the string ".T.", and false by ".F.", while in Part 28 (XML) they are represented by text strings "true" and "false".

context (Type='CLASS')

The name of the class being used to classify the representation context (Numerical_representation_context) of the property. The 'Representation context' defined below is a root classification. Other (subclasses) of this may be used instead.

The following classes and their sub-classes can be used:

classifications: "Representation_context" (urn:plcs:rdl:std:Representation_context)

context_ecl_id (Default=urn:plcs:rdl:std,Type='URN')

The identifier of the External_class_library storing the definition of the class referenced by the parameter @context.

Reference parameters

The following reference parameters are defined for this template:

representation(Type='ENTITY (Property_value_representation)')

Allow the Property_value_representation entity instantiated in this path to be referenced when this template is used.

Note: The Property_value_representation entity can be referenced in a template path by:

%^target = $representing_value_w_tolerances.representation%

where target is the parameter to which the Property_value_representation is bound.

num_rep_cntxt(Type='ENTITY (Numerical_representation_context)')

Allow the Numerical_representation_context entity instantiated in this path to be referenced when this template is used.

Note: The Numerical_representation_context entity can be referenced in a template path by:

%^target = $representing_value_w_tolerances.num_rep_cntxt%

where target is the parameter to which the Numerical_representation_context is bound.

Uniqueness constraints

The following parameter combinations specify a uniqueness constraint:

Unique constraint: Unique numerical representation context

Each instance of the entity (Numerical_representation_context) within the data set shall be uniquely identified by a combination of the following parameters on this template (representing_value_w_tolerances) namely: context, context_ecl_id.
The instance is referenced by the following template parameter: num_rep_cntxt.

There will be one numerical context for the representation of a value.

Instantiation path

The instantiation path shown below specifies the entities that are to be instantiated by the template.

A description of templates and the syntax for the instantiation path is provided in the Templates Help/Information section.

-- Instantiate Property_value_representation entity
Property_value_representation

-- Set the Property_value_representation attributes id, name and description to be ignored
Property_value_representation.id = '/IGNORE'
Property_value_representation.name = '/IGNORE'
Property_value_representation.description = '/IGNORE'

-- Bind the Property_value_representation to the parameter ^representation.
-- The parameter is a reference parameter so the Property_value_representation
-- entity can be referred to when this template is used.
%^representation = Property_value_representation%

-- Instantiate Numerical_representation_context and assign
-- Property_value_representation at it
%^num_rep_cntxt = Numerical_representation_context%

-- Set the Numerical_representation_context attributes id and kind to be ignored
Numerical_representation_context.id = '/IGNORE'
Numerical_representation_context.kind = '/IGNORE'
^representation.context_of_items -> ^num_rep_cntxt

-- Assign reference data for kind of Numerical_representation_context
/assigning_reference_data(
    items=^num_rep_cntxt,
    class_name=@context,
    ecl_id=@context_ecl_id)/

-- Instantiate Value_with_tolerances and assign
-- Property_value_representation to it
^representation.items -> Value_with_tolerances

-- Set the Value_with_tolerances attributes
Value_with_tolerances.name = '/IGNORE'
Value_with_tolerances.upper_limit = @upper_limit
Value_with_tolerances.lower_limit = @lower_limit

-- Instantiate template representing_numerical_item
-- for value
/representing_numerical_item(
    value= @value,
    unit= @unit,
    unit_ecl_id= @unit_ecl_id,
    si_unit= @si_unit)/

-- Bind ref param ^item in just instantiated template
-- representing_numerical_item to ref param ^item in this template,
-- and point attribute Value_with_tolerances.item_value to it
%^item = $representing_numerical_item.item%
Value_with_tolerances.item_value -> ^item

The following entities are instantiated with attributes as specified:

Entity in path	Value	Inherited from
Property_value_representation.id	'/IGNORE'	Representation.id
Property_value_representation.name	'/IGNORE'	Representation.name
Property_value_representation.description	'/IGNORE'	Representation.description
Numerical_representation_context.id	'/IGNORE'	Representation_context.id
Numerical_representation_context.kind	'/IGNORE'	Representation_context.kind
Value_with_tolerances.name	'/IGNORE'	Representation_item.name
Value_with_tolerances.upper_limit	@upper_limit	—
Value_with_tolerances.lower_limit	@lower_limit	—

Instance diagrams

The instance diagram in Figure 3 shows an example of the EXPRESS entities and templates that are instantiated by the template:

/representing_value_w_tolerances(value='ANY_NUMBER_VALUE(35)', lower_limit='-4.0', upper_limit='0.5', unit='kilogram', unit_ecl_id='urn:plcs:rdl:std', si_unit='.T.', context='Representation_context', context_ecl_id='urn:plcs:rdl:std')/

(an illustration of the consolidated representing_value_w_tolerances template is shown in Figure 4 below.)

Figure 3 — Entities instantiated by representing_value_w_tolerances template.

The instance diagram in Figure 4 shows the graphic symbol for the template that is to be used in other instance diagrams. The example template is:

Figure 4 — Instantiation of representing_value_w_tolerances template

Characterizations

The following section details how the representing_value_w_tolerances template can be optionally characterized by assigning other constructs to it. These are characterizations commonly applied to the template. The ISO 10303-239 EXPRESS model may enable other assignments to the entities instantiated by the template.

The EXPRESS-G diagram in Figure 5 shows the possible characterizations of the template "representing_value_w_tolerances".

Figure 5 — Characterizations for representing value with tolerances template

The following characterizations may apply:

Characterization Assigning time (and Dates)

NOTE this characterization is optional.

Time (and dates) can be associated with the assignment of a property value representation as shown in Figure 5, by using the templates assigning_time. An example of this is provided below.

Figure 6 — Characterization by date of representing_value_w_tolerances template

The date of creation of the property value representation is represented by using the template assigning_time to assign a date and time to Property_value_representation (reference parameter ^representation in template representing_value_w_tolerances). The date and time assignment is classified as: "Date actual creation" (urn:plcs:rdl:std:Date actual creation) to indicate that it is the date (and time) when the property value representation was actually created. This is illustrated in Figure 6.

Other dates may be assigned instead.

Characterization Assigning organization or person

NOTE this characterization is optional.

An Organization (or a Person_in_organization) can be associated with the property value representation (see the ^representation reference parameter), as in Figure 5. The creating organization is represented by using the template assigning_organization or assigning_person_in_organization assigned to Property_value_representation (reference parameter ^representation in template representing_value_w_tolerances). The assignment of the organization (Organization_or_person_in_organization_assignment) is classified as: "Creator of" (urn:plcs:rdl:std:Creator of) to indicate that this organization created the property value representation. This is illustrated in Figure 7.

Figure 7 — Characterization by organization or person of representing_value_range template

Other roles of an organization with regard to a property value representation may be assigned instead.