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Display attribute (with a legend)

The process of displaying an attribute with a legend as defined in the attribute value look-up-table involves the following steps:

1. Get colour name definitions

2. Get a list of active themes

3. Get a list of all attributes in the active theme

4. Get the proper data set member definition file

5. Get the definitions of the active theme

6. Get the data set member attribute definition file of the active theme

7. Select the attribute to display

8. Get the proper attribute value look-up-file

9. Update the legend and theme display based on the contents of the attribute value look-up-table

These steps are described in more detail in the following:

Get colour name definitions

The colour names used by this INSROP GIS function are defined in an AVENUE script called INSROP.RGBColorNameDictionary. These colour name definitions are similar to the UNIX colour name definitions. This step requires no user input.

Get a list of active themes

If there are active themes, they are put in a list and processed one at a time. If no themes are active the user is asked to make a theme active and try again. If there is more than one active theme, the following sequence of steps is repeated for each active theme. This step requires no user input.

Get a list of all attributes in the active theme

This step is useful when there are more than one active theme. If subsequent active themes have the same attributes, Steps 4-8 are only carried out for the first of these themes, and the information obtained then are used for all the remaining themes in the sequence. This step requires no user input.

Get the proper data set member definition file

This step searches for a data set member definition file in the directory where the active theme is stored. If more than one is found, the user is prompted to select the proper data set member definition file. If none are found, INSROP GIS assumes that the data set member attribute definition file ia called alias.fld and Step 5 is skipped.

Get the definitions of the active theme

A theme is a data set member, and the data set member definition file from Step 4 may comprise the theme definitions. Only the Theme-ID is a mandatory definition parameter. If no Theme-ID satisfying the active theme is found, or the Aliasfile column value is empty, INSROP GIS assumes that the data set member attribute definition file ia called alias.fld.

Get the data set member attribute definition file of the active theme

If not already existing in the project, this file is added to the project as a table document. To determine whether the file already exists, INSROP GIS checks whether the table name and comments (see Table-Properties) are identical. The table comments are taken from the comment line (Line 2) in the data set member attribute definition file when the table is added to the project. If no suitable data set member attribute definition file is found, the user is prompted for one.

Select the attribute to display

The data set member attribute definition file should comprise definition parameters for the attributes the user is allowed to display with this INSROP GIS function. As the function is intended for unique classification, there should only be a limited set of possible attribute values. If the number of different attribute values is large, we recommend using Theme-Classify Attribute instead.

The user is prompted to select one attribute to display.

Note:

To use a specified default symbol/colour (not depending on a particular attribute value), use "Default" in the attribute Fieldname column in the data set member attribute definition file and in the Value column in the attribute value look-up-file.

Get the proper attribute value look-up-file

The name of this file was defined in the data set member attribute definition table. If not already existing in the project, this file is added to the project as a table document. To determine whether the file already exists, INSROP GIS checks whether the table name and comments (see Table-Properties) are identical. The table comments are taken from the comment line (Line 2) in the attribute value look-up-file when the table is added to the project. If no suitable attribute value look-up-file is found, the user is prompted for one.

Update the legend and theme display based on the contents of the attribute value look-up-table

Based on the actual attribute values in the active theme and the attribute value look-up-table, the display of features in the theme and the associated legend is updated. If there are more than one active theme, the process will now start over at Step 3 until all active themes are processed, or the user has Cancelled the process.