Feature classes in a geodatabase in Informix

A feature class is a collection of geographic features, all of the same geometric type (point, line, polygon, multipoint, annotation, dimension, or multipatch). For example, you could store points for all the train depots along a railroad line in one feature class. In another feature class, you could store lines that represent all the railroad tracks.

This topic contains descriptions of the way a feature class appears in the Catalog window, in the database management system (DBMS), and in an XML document.

Feature classes in ArcGIS Desktop

There are seven types of feature classes you can create in ArcGIS Desktop: point, multipoint, line, polygon, annotation, dimension, and multipatch.

You can tell what type of feature class it is in the Catalog tree based on the icon. The following table shows the icon for each type of feature class.

Feature class icon	Type of feature class
	Point or multipoint
	Line
	Polygon
	Annotation
	Dimension
	Multipatch

In IBM Informix, the name of a feature class as it appears in the Catalog tree includes the name of the database the feature class is in followed by a colon(:), the name of the user who owns the feature class, and the name of the feature class itself.

For example, a feature class named parcels, owned by user RJP, in a geodatabase named geodata is listed as geodata:RJP.parcels in the Catalog tree.

For a description of the different types of feature classes, see Feature class basics.

Feature classes in an IBM Informix database

Feature classes stored in geodatabases in an Informix database have an ST_Geometry column, which is used to store geometry data. That means an ST_Geometry column is added to the business table of the feature class.

ST_Geometry is an abstract noninstantiable superclass, the subclasses of which are instantiable. See What is the ST_Geometry storage type? for more information.

When a feature class is created through ArcGIS using ST_Geometry storage, a business table with an ST_Geometry column is created in the owner's schema. Also, records are added to the layers, table_registry, sde_geometry_columns, column_registry, sde_spatial_references (if a spatial reference was defined), and gdb_items tables in the sde user's schema to track information about the feature class. The gdb_itemtypes table in the sde user's schema defines the type of data it is, in this case, feature class.

All feature classes have a business table, which stores attribute information, an ObjectID, and a Shape field. The ObjectID and Shape fields can have different names, but they are required to be in the business table of a feature class.

Once you have loaded data, you will have several i tables and stored procedures in your database. These stored procedures and i tables are used for generating feature IDs for feature classes. The i tables contain a number in their name. This number corresponds to the registration_id of the feature class in the table_registry table. Editing these tables or stored procedures is not supported and highly discouraged.

View a diagram of a feature class in Informix.

You need Adobe Acrobat Reader to open the file.

Dashed lines indicate implicit relationships between columns; solid lines indicate explicit relationships between columns.

Tip:

Annotation and dimension feature classes have additional required fields in their business tables. See Managing annotation feature class properties for a list of these fields.

Feature classes stored in an XML document

Feature classes are defined within DataElement elements. The DataElement tags for a feature class are set to type esri:DEFeatureClass. Within the feature class DataElement are other elements that define the feature class, such as Field, Domain, ConfigurationKeyword, and SpatialReference elements.

The following is a small portion of the content of an XML document for the Parcels feature class:

<DataElement xsi:type="esri:DEFeatureClass">
   <CatalogPath>/V=sde.DEFAULT/FC=geodata:rjp.parcels</CatalogPath> 
      <Name>geodata:rjp.parcels</Name> 
      <DatasetType>esriDTFeatureClass</DatasetType> 
      <DSID>11</DSID> 
      <Versioned>false</Versioned> 
      <CanVersion>true</CanVersion> 
      <HasOID>true</HasOID> 
      <OIDFieldName>objectid</OIDFieldName> 
      <Fields xsi:type="esri:Fields">
         <FieldArray xsi:type="esri:ArrayOfField">
            <Field xsi:type="esri:Field">
              <Name>sde92:world.lakes.objectid</Name> 
              <Type>esriFieldTypeOID</Type> 
              <IsNullable>false</IsNullable> 
              <Length>4</Length> 
              <Precision>10</Precision> 
              <Scale>0</Scale>
              <Required>true</Required>
              <Editable>false</Editable>
              <AliasName>OBJECTID</AliasName>
              <ModelName>OBJECTID</ModelName>
            </Field>               

All other elements defining the feature class

</DataElement>