Class Name: Property Table Reference

Superclass - <SEDRIS Abstract Base>

Subclasses

Definition

An instance of this DRM class specifies a reference to an (N-1)-dimensional slice of an N-dimensional <Property Table> component of a <Data Table Library> instance, where N is the number of <Axis> components of the <Property Table> instance.

The <Property Table Reference> class exists primarily to allow a data provider to select a set of parameters from a standard <Property Table> instance containing an indexed collection of alternatives.

Since only one <Axis> instance requires a specific tick mark to be specified, a <Property Table Reference> instance specifies the axis_type of the <Axis> instance to be matched, and the index_on_axis specifies the tick mark on that <Axis> instance.

Primary Page in DRM Diagram:

• 6

Secondary Pages in DRM Diagram:

• 3
• 8
• 16
• 18
• 19
• 22

Example

1. See the <Property Table Reference Control Link> class, second example.

FAQs

Why not use a collection of <Property Value> instances instead of a <Property Table Reference> instance?

In some cases this might be possible, and is not prohibited. However, some tables are multi-dimensional. It would not be possible to define <Property Value> instances to designate each combination of axis values that occur in a multi-dimensional table.

Why an N-1 dimensional slice?

This is the only case for which there is a currently identified need, given the recursive composition capabilities of the <Property Table> class.

What restrictions are there on axis_type?

The referenced <Property Table> instance shall contain an <Axis> component with a matching axis_type; otherwise, there are no restrictions. Any <Axis> component within the target <Property Table> instance may be specified.

Why is index_on_axis a zero-based index?

Because the corresponding <Axis> data structures for tick marks are C arrays, and C uses zero-based indexes for arrays.

Constraints

• <<Publishable Object>>
• <<Characteristics Of Property Table Reference>>
• <<Constraints On Associates>>

Associated to (one-way)

• one <Property Table> instance

Composed of (two-way)

• zero or one <Property Table Reference Control Link> instance

Component of (two-way)

• zero or more <Feature Representation> instances
• zero or more <Geometry Representation> instances
• zero or more <Image> instances
• zero or more <Predefined Function> instances
• zero or more <Property Set> instances
• zero or more <Property Table> instances
• zero or more <Vertex> instances

Inherited Field Elements

Field Elements

Notes

Fields Notes

axis_type

The axis_type field specifies the property being described by the target <Axis> instance.

index_on_axis

The index_on_axis field specifies the (zero-based) index of the tick mark being referenced on the specified <Axis> instance. This allows the tick mark to be specified in a manner independent of the class of the <Axis> instance. The only restriction is that the value of index_on_axis shall be between zero and axis_value_count-1 for the specified <Axis> instance.

If index_on_axis specifies some value j, the (j+1)^th tick mark on the <Axis> instance is being referenced regardless of the data type of the tick marks specified by the specific subclass of <Axis> being used.

For a <Property Table Reference> instance with a <Property Table Reference Control Link> component X, the value of the index_on_axis field is obtained from X.