ISO 10303-214:2010(E)
A Size_dimension is the representation of the size of an individual shape element.
NOTE Size_dimension as defined in this part of ISO 10303 describe an intrinsic length or angle characteristic of part shape. This includes characteristics of what are traditionally called "features-of-size", but they are not limited to that usage alone. For example, the radial_size_dimension and curved_size_dimension application objects describe characteristics which may not be applied to "features-of-size.
A Size_dimension is a type of Geometric_dimension.
Each Size_dimension is an Angular_size_dimension, a Thickness_dimension, or a Externally_defined_size_dimension.
The data associated with a Size_dimension are the following:
envelope
The envelope specifies whether the envelope principle applies or not. A value of 'true' indicates that the envelope principle applies to this size dimension. When the envelope principle applies, the envelope of the perfect shape corresponding to the maximum material shall not be larger than the specified dimension and tolerance. The envelope principle specifies that size and form tolerances are not additive.
NOTE 1 The concept of the envelope principle is defined in ISO 1101 [9].
NOTE 2 A dimension where the envelope principle applies, appears on drawings with an 'E' enclosed in a circle following the dimension value.
NOTE 3 The envelope principle may have counterparts in other standards.
EXEMPLE The envelope principle is equivalent to ASME Y14.5 rule 1 The envelope need not be specified for a particular Value_limitation.
is_applied_to
The is_applied_to specifies the geometric or annotation element which the Size_dimension is applied to.
See size_dimension to annotation_curve and size_dimension to shape_element for the application assertions.
There shall be exactly one object that the Size_dimension is_applied_to.
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