What is a theme?

A theme is a set of geographic features in a view, and represents one of the following sources of geographic data:

INSROP00090000.gif A spatial data source such as an "ARC/INFO coverage" or "ArcView shapefile". Most ARC/INFO coverages contain several different classes of features, such as polygons and label points, in which case only one of these classes is represented in the theme. An ArcView shapefile can represent point, line or polygon features. You can edit the features of a theme that is based on the ArcView shapefile format.

INSROP00090000.gif An image data source such as a satellite photo.

INSROP00090000.gif A tabular data source containing events such as a table with XY coordinates, or a file of customers that ArcView can geocode.

This data can be on a local disk or accessed across a network. A theme points to the geographic data it represents. It does not contain the data itself.

The themes in a view are listed in its Table of Contents. For example, a view of a country might have one theme representing cities, one theme representing roads, one representing an satellite image, etc.

Normally, a theme represents all the features in a particular feature class, but you can also define a feature selection property for a theme so that it only represents a specific subset of these features. For example, if you have a data source containing roads you can define a theme that represents just the major roads.

Themes have a number of other properties that you can set to control their characteristics. For example, you can specify the range of scales at which the theme will be drawn on the view.

Each theme has its own legend displayed in the Table of Contents. A theme's legend controls how the theme is displayed on the view. To change the colors and symbols used to display a theme, you edit the theme's legend.


See also

What is a view?