The SEDRIS Data Representation Model
APPENDIX A - Classes
Irregular Axis

Class Name: Irregular Axis

Superclass - <Axis>

Subclasses

This DRM class is concrete and has no subclasses.

Definition

An instance of this DRM class is an <Axis> instance that does not use a constant spacing between hash marks.

Primary Page in DRM Diagram:

Secondary Pages in DRM Diagram:

This class appears on only one page of the DRM class diagram.

Example

  1. Data taken at times 1, 2, 5, 10, 50, and 100 seconds after some start time would be collected on an <Irregular Axis> instance.

  2. Radiosonde data, including temperature, humidity, wind speed, and wind direction, is generally reported as a function of pressure height. Data are reported only when there is a significant change in one of the dependent variables. Accordingly, the pressure heights are captured at unpredictable, irregular intervals. They are best captured in an <Irregular Axis> instance.

FAQs

If a few values are missing from a regular sequence, should the data provider use an <Irregular Axis> instance to represent the data?

It depends how many values are missing. If only one or two values are missing from a long regular sequence, it may be preferable to use a <Regular Axis> instance and indicate the missing data points with an appropriate <Property Characteristic> instance.

A data provider's data was taken on an irregular set of points on a surface. Should <Irregular Axis> instances be used to indicate the 2-dimensional locations of these points?

If the data were truly irregular, which is to say that there is only one point at each x-value and only one point at each y-value, do not use irregular x- and y-axes. Instead, use a single regular axis to give each point an index and make the x- and y-values dependent variables.

On the other hand, if the points are not quite that irregular, but rather data were taken at each (or most) combination of x- and y-values, irregular axes may be appropriate. This would mean that the data really did form a grid.

Constraints

Component of (two-way) (inherited)

Inherited Field Elements

EDCS_Attribute_Code axis_type; (notes)
SE_Short_Integer_Positive axis_value_count; (notes)

Field Elements

SE_Single_Value axis_value_array[]; (notes)
EDCS_Unit_Code value_unit; (notes)
EDCS_Scale_Code value_scale; (notes)
SE_Interpolation_Type interpolation_type; (notes)

Notes

Fields Notes


axis_type

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

axis_value_count

 The axis_value_count field specifies the number of "hash marks"
 along the given <Axis> instance.

axis_value_array

 The axis_value_array field specifies the "tick mark" values, which
 shall be arranged in ascending order.

value_unit

 The value_unit field specifies the unit of measurement of the given
 <Irregular Axis> instance, which shall be compatible with the
 requirements imposed by  its axis_type value.

 If the specified axis_type does not require a unit of measurement
 value_unit shall be set to EUC_UNITLESS.

value_scale

 The value_scale field specifies the scale applicable to value_unit.

 If the specified axis_type does not require a unit of measurement,
 value_scale shall be set to ESC_UNI.

interpolation_type

 The value of the interpolation_type field allows the data provider
 to indicate how best to interpolate the data to points that are
 between grid points on the axis represented by the given
 <Irregular Axis> instance. Note that when a <Data Table> instance
 has more than one <Irregular Axis> component, the order of the
 interpolations follows the order of the <Irregular Axis> components.
Prev: Interval Axis. Next: Keywords. Up:Index.

Last updated: July 16, 2004 Copyright © 2004 SEDRIS™