Understanding coverage attribute tables

Feature attribute tables are special sets of tables created for various feature classes. Feature attribute tables are INFO data files that contain a number of predefined items and additional user-defined attributes for each feature. A number of feature attribute tables can be created for a coverage, each associated with a particular feature class. A feature attribute table is named after the coverage with a three-letter code indicating the type of feature attribute table. For example, a coverage named LOTS that contains polygons will have a polygon attribute table (PAT) named LOTS.pat.

The following table describes the feature attribute tables that can exist within a coverage:

Feature class	Feature attribute table naming convention	Description
Point	<cover>.pat	Point attribute table
Arc	<cover>.aat	Arc attribute table
Node	<cover>.nat	Node attribute table
Route	<cover>.rat<route>	Route attribute table
Section	<cover>.sec<route>	Section attribute table
Polygon	<cover>.pat	Polygon attribute table
Region	<cover>.pat<region>	Region attribute table
Annotation	<subclass>.tat	Text attribute table

The feature attribute tables that can exist within a coverage

Feature attribute tables have special item formats and standards. A minimum set of items is always found in each feature attribute table. For example, each PAT always contains at least four items: AREA, PERIMETER, COVER#, and COVER-ID.

Point attribute tables have the same .pat extension and contain the same items as polygon attribute tables. For this reason, a coverage cannot contain both point and polygon features.

There is always one record in the feature attribute table that corresponds to each feature in the coverage. Both the spatial information used to define the coverage feature and the corresponding record in the feature attribute table contain the feature number so that a one-to-one correspondence is maintained between the feature and its attribute record.

You can add items to a feature attribute table and use them as keys to relate other attribute information to features. Thus, the feature attribute table acts as a key table between coverage features and additional attribute information about each feature. Even though the records in a feature attribute table maintain a one-to-one correspondence with coverage features, one-to-many and many-to-many relationships can be managed between the feature attribute table and corresponding tables.