Table 6.278 — DRM_Time_Related_Geometry

Property

Description

Class
  • <DRM Time Related Geometry>

Superclass

Subclass
  • None.

Definition

An instance of this DRM class is an aggregation of <DRM Geometry Hierarchy> instances, in which each branch is a representation of the same environmental entity at a different point in time, as indicated by the corresponding <DRM Time Constraints Data> instance.

The time_data_type field specifies the subclass of <DRM Base Time Data> of which each <DRM Time Constraints Data> link object in the given organization is to be composed.

Clarifications

1 An association between a <DRM Feature Representation> instance and a <DRM Geometry Hierarchy> instance indicates that the environmental object(s) that they represent have the semantic relationship indicated by the <DRM Base Association Data> instance on the association relationship.

2 An association between two <DRM Geometry Hierarchy> instances indicates that the environmental object(s) that they represent have the semantic relationship indicated by the <DRM Base Association Data> instance on the association relationship.

3 An association between a <DRM Feature Representation> instance and a <DRM Geometry Hierarchy> instance indicates that the environmental object(s) that they represent have the semantic relationship indicated by the <DRM Base Association Data> instance on the association relationship.

4 An association between two <DRM Geometry Hierarchy> instances indicates that the environmental object(s) that they represent have the semantic relationship indicated by the <DRM Base Association Data> instance on the association relationship.

5 An association from a <DRM Hierarchy Summary Item> instance to a <DRM Geometry Hierarchy> indicates that the <DRM Hierarchy Summary Item> instance summarizes that <DRM Geometry Hierarchy> instance.

6 An association from a <DRM Reference Surface> instance to a <DRM Geometry Hierarchy> instance indicates that the <DRM Geometry Hierarchy> instance organizes the geometric objects that specify the resolution surface of the <DRM Reference Surface> instance.

7 In the case where multiple <DRM Collision Volume> components are specified for a given <DRM Aggregate Geometry> instance, the union of the volumes thus specified is used in collision detection.

Class diagram

Figure 6.332 — DRM_Time_Related_Geometry

Inherited field elements

Field name

Range

Field data type

unique_descendants

 

Boolean

strict_organizing_principle

 

Boolean

Field elements

Field name

Range

Field data type

time_data_type

 

Time_Data_Type

Associated to (one-way) (inherited)

Associated to (one-way)
  • None.

Associated by (one-way) (inherited)

Associated by (one-way)
  • None.

Associated with (two-way) (inherited)
  • None.

Associated with (two-way)
  • None.

Composed of (two-way) (inherited)

Composed of (two-way)

Composed of (two-way metadata) (inherited)

Composed of (two-way metadata)
  • None.

Component of (two-way) (inherited)

Component of (two-way)
  • None.

Constraints

Example(s)

  • Consider atmospheric forecast data organized using nested <DRM Time Related Geometry> instances as shown in Figure 6.333.

    Time Related Geometry, Example 1

    Figure 6.333 — <DRM Time Related Geometry> example

    The <DRM Classification Data> instances specify to what each <DRM Time Related Geometry> instance corresponds. The outer <DRM Time Related Geometry> instance corresponds to base forecast times, while the inner <DRM Time Related Geometry> instance corresponds to forecast taus.

    In the forecast world, models are run starting at some base starting time (for example, at 0Z and 12Z). The model then produces forecasts at several deltas after the base starting time (for example, at 6, 12, 18, and 24 hours). These are known as forecast taus.

    Consequently, when forecast models are run at 0Z and 12Z, and each produces a 24-hour forecast, the following overlap is obtained. 

        16 Nov                 17 Nov                     18 Nov
    0Z   +6    +12   +18   +24
               12Z   +6   +12    +18    +24
                           0Z    +6     +12    +18    +24
                                  etc.

    To uniquely identify a forecast, the base forecast time and the delta (tau) are required. Nested <DRM Time Related Geometry> are used in this example; one <DRM Time Related Geometry> defines the base forecast time, while its component <DRM Time Related Geometry> defines the forecast tau.

    This approach is needed only if multiple forecasts with overlapping forecasts are included in the transmittal. If instead the analysis (0Z) and +6 forecasts from each forecast are used, the following would be obtained. 

        16 Nov             17 Nov
    0Z   +6  12Z  +6   0Z   +6   12Z   +6  ...

  • Consider a <DRM Model> instance of a deciduous tree. The colour of the tree’s leaves depends on the time of year, or season. Consequently, a data provider might organize a tree <DRM Model> instance using a <DRM Time Related Geometry> instance along the lines depicted in Figure 6.334. (Only the autumn representation of the <DRM Model> is shown, but other branches are present for the other seasons).

    Time Related Geometry, Example 2

    Figure 6.334 — <DRM Time Related Geometry> example