Property Description

The SEDRIS Data Representation Model APPENDIX A - Classes Property Description

Class Name: Property Description

Superclass - <Property>

Subclasses

This DRM class is concrete and has no subclasses.

Definition

An instance of this DRM class is used to elaborate a property of an <Aggregate Geometry> instance or <Aggregate Feature> instance and/or its component inheritance subtree by specifying <Property Characteristic> components and/or qualifying <Property Value> components that meaningfully limit the property identified by the <Property Description> instance.

Primary Page in DRM Diagram:

Secondary Pages in DRM Diagram:

Example

Consider a <Union Of Primitive Geometry> instance containing <Polygon> instances, each of which has an emissivity applicable to the infrared band only, where valid values are less than or equal to 1.0, as depicted in Figure 41.

Figure 41 — <DRM Property Description> infrared emissivity example

The emissivity of each <Polygon> instance is applicable to the infrared band only, because that property is so qualified by inheritance.
Consider a <Union Of Features> instance containing various <Primitive Feature> instances that shall specify dewpoint temperature. For all the <Primitive Feature> instances in this aggregate, the dewpoint temperature given was taken at a height of ten metres above the surface of the terrain, and is of good quality, as depicted in Figure 42.

Figure 42 — <DRM Property Description> dewpoint temperature example

Since the <Point Feature> instance's <Property Value> component describes EAC_DEWPOINT_TEMPERATURE, it inherits the following qualifiers:
1. The EAC_DEWPOINT_TEMPERATURE measurement was taken at a height of ten metres above the surface.
2. The measurement is of good quality.

FAQs

How does an aggregate object use a <Property Description> instance?

In two ways, either separately or in combination.

An aggregate may use a <Property Description> instance to specify <Property Characteristic> components (such as maximum value for a quantity).
An aggregate might also use a <Property Description> instance's <Property Value> components to qualify an EAC.

All objects in the component inheritance tree of the aggregate, as long as they have <Property Value> instances with a matching EAC, are subject to the <Property Description> instances and/or qualifying values.

Can a data provider qualify an attribute A with two sets of qualifying <Property Value> instances, {b1, c1} and {b2, c2} by associating two <Property Value> instances for A with the corresponding qualifier set?

No. This situation requires a <Property Table> instance.

Are there any restrictions on the <Property Value> components?

Only semantic restrictions. For example, it makes sense to limit the applicability of an electromagnetic emissivity value to a particular electromagnetic band. But it would be nonsensical to limit an electromagnetic band to a particular emissivity value.