The SEDRIS Data Representation Model
APPENDIX A - Classes
Axis

Abstract Class Name: Axis

Superclass - <SEDRIS Abstract Base>

Subclasses

Definition

An instance of this DRM class specifies a set of values of an independent variable to be used to organize the dependent values in a <Data Table> instance.

Primary Page in DRM Diagram:

Secondary Pages in DRM Diagram:

Example

  1. A table containing data imported from DTED contains terrain elevation data sampled in a grid of regularly spaced longitude and latitude points. The <Axis> components of such a <Data Table> instance - specifically, <Regular Axis> components - are longitude and latitude.

  2. A table of ocean temperature and salinity data taken at varying depths by an expendable bathythermograph can be captured in a table. Such a <Data Table> instance has EAC_WATER_DEPTH as an <Irregular Axis> component, EAC_WATERBODY_TEMPERATURE and EAC_WATERBODY_SALINITY are <Table Property Description> components. If these data were taken at intervals along a path, the locations on that path (say longitudes) forms a second <Axis> component - specifically, an <Interval Axis> component - of the now two-dimensional table.

FAQs

How are the values on an <Axis> instance related?

The values on a single <Axis> instance X shall be distinct values of a single variable specified by the axis_type field of X.

Can an <Axis> instance have no tick mark values?

No. An <Axis> instance shall have at least one tick mark value.

Can an <Axis> instance have exactly one tick mark value?

Yes; this case implies that all of the data in the cells of the corresponding <Data Table> instance share that value.

Given two variables, where certain combinations of values for these two variables are impossible or meaningless, can a data provider combine these two variables on a single <Axis> instance in order to exclude the meaningless cells?

No. In such a case, the data provider should specify a value for EVC_NOT_APPLICABLE, and use it for those cells. See <Table Property Description> and <Property Characteristic> for more information.

Constraints

Component of (two-way)

Inherited Field Elements

This class has no inherited field elements.

Field Elements

EDCS_Attribute_Code axis_type; 1
SE_Short_Integer_Positive axis_value_count; 2

Notes

Fields Notes

axis_type

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

axis_value_count

The axis_value_count specifies the number of tick marks along the <Axis> instance.


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Last updated: July 26, 2006 Copyright © 2006 SEDRIS