The SEDRIS Data Representation Model
APPENDIX A - Classes
Table Property Description

Class Name: Table Property Description

Superclass - <Property>

Subclasses

This DRM class is concrete and has no subclasses.

Definition

An instance of this DRM class describes a cell data element within a <Data Table> by providing

  1. an EDCS Attribute Code, SE_Index_Code, or SE_Variable_Code, identifying the meaning of the cell data element,

  2. a value_type that specifies its storage type,

  3. an EDCS Unit Code (EUC) and EDCS Scale Code (ESC) that together specify the scaled unit of measurement.

The complete structure of a cell within the given <Data Table> is described by the complete ordered set of <Table Property Description> components of that <Data Table>.

Additional information about the cell property being described, where such information is to be applied throughout the scope of the <Data Table>, such as sentinel values and tolerances, is specified by attaching <Property Characteristic> components to the applicable <Table Property Description>(s).

Primary Page in DRM Diagram:

Secondary Pages in DRM Diagram:

Example

  1. Consider a <Property Grid> containing sound speed data for a body of water. For each spatial location in the grid, the corresponding cell in the <Property Grid> specifies the properties of EAC_SALINITY, EAC_MEAN_WATER_BODY_TEMPERATURE, and EAC_WATER_BODY_SOUND_SPEED at that location. 

                 <Property Grid>
                     <>
                     |
                     |-- <Table Property Description>
                     |   meaning = { SE_ELEM_CODE_TYP_ATTRIBUTE,
                     |               { EAC_SALINITY }}
                     |
                     |-- <Table Property Description>
                     |   meaning = { SE_ELEM_CODE_TYP_ATTRIBUTE,
                     |               { EAC_MEAN_WATER_BODY_TEMPERATURE }}
                     |
                     |-- <Table Property Description>
                     |   meaning = { SE_ELEM_CODE_TYP_ATTRIBUTE,
                     |               { EAC_WATER_BODY_SOUND_SPEED }}
                     |
                     | (other components, such as <Axis> objects)

FAQs

Why is the value_type field needed?

The storage type of each cell data element shall be specified, and each cell data element shall be allowed to specify its own storage type. This means that the storage type information cannot be stored in the <Data Table>'s own fields, but shall be specified at the <Table Property Description> level.

Unlike <Property Value>, which contains a complete SE_Property_Data_Value, <Table Property Description> only needs to to specify the storage type without a value being stored, since the values being described are the cells of the <Data Table>, rather than any part of the <Table Property Description> itself.

What is the purpose of the component_data_table_ecc field and the optional <Property Value> components?

Consider a <Data Table> instance with more than one <Table Property Description> supplying the same SE_Index_Code as a meaning, where that meaning is that each such <Table Property Description> acts as a signature element to reference other <Data Tables>.

In these cases, the component_data_table_ecc, possibly elaborated by optional <Property Values>, is needed to distinguish index values in any given cell.

See <Classification Data> and the <<Index Codes within Tables>> constraint for further information.

Constraints

Composed of (two-way)(inherited)

Composed of (two-way)

Component of (two-way)

Inherited Field Elements

SE_Element_Type meaning; (notes)
EDCS_Unit_Code value_unit; (notes)
EDCS_Scale_Code value_scale; (notes)

Field Elements

SE_Property_Data_Value_Type value_type; (notes)
EDCS_Classification_Code component_data_table_ecc; (notes)

Notes

Composed of Notes


Property_Value

 These components are provided only when the given
 <Table Property Description> serves as an index into another
 <Data Table>, specifically, when the target <Data Table>'s
 <Classification Data> is elaborated by <Property Value> components.

 When such elaboration is present in the target, the
 <Property Value> components of this <Table Property Description>
 shall match those in the target.

Fields Notes


meaning

 This specifies the meaning of the given <Property> instance.

value_unit

 This specifies the unit of measurement of the given <Property> instance.

value_scale

 This specifies the scale applicable to value_unit.

value_type

 This specifies the storage type of the given
 <Table Property Description> instance.

component_data_table_ecc

 This is the EDCS Classification Code used to identify the table type
 of a component or library <Data Table>.  It is only used if this
 <Table Property Description> is describing an index that refers
 to a <Data Table>
 (This is only the case if
       meaning = { SE_ELEM_CODE_TYP_INDEX,
                    {SE_INDEX_CODE_DATA_TABLE_COMPONENT }} and
       value_type  = SE_PDV_DATA_TABLE_COMPONENT_INDEX
       value_unit  = EUC_UNITLESS and
       value_scale = ESC_UNI and
 or
       meaning = { SE_ELEM_CODE_TYP_INDEX,
                    {SE_INDEX_CODE_DATA_TABLE_LIBRARY }} and
       value_type  = SE_PDV_DATA_TABLE_LIBRARY_INDEX
       value_unit  = EUC_UNITLESS and
       value_scale = ESC_UNI and

 Otherwise component_data_table_ecc is ignored.
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Last updated: May 15, 2003 Copyright © 2003 SEDRIS™