A [i]group[/i] is a named set of attribute keys. An attribute key can belong to many groups or none at all. An [i]attribute key[/i] describes named values attached to a particular type of object. Each instance of this entity contains the attribute's description and its name. An attribute key name must consist of letters, numbers, periods, underscores, and hyphens. Text describing the attribute. This should explain what the attribute means and what kinds of values are appropriate. ERDB data type for the attribute. This serves as documentation only, but that may change at some future point. An [i]object[/i] represents a keyed thing to which an attribute can be assigned. In order to improve performance, this table has no data in it. It is simply required by the semantics of the database. This relationship connects an attribute key to the groups of which it is a member. This relationship connects an attribute key to its objects. It contains the attribute values, and is therefore the primary data repository for the database. Some attribute keys are split into two parts. The real key is controlled and must correspond to a key in the AttributeKey table. The second part of the key resides in this field. When the attribute value is presented to the user, the two parts of the key are joined together around the splitter value. This is the actual attribute value. Note that a single key/object pair may in fact have many values, and therefore many entries in this table. This index sorts all the values for a single attribute key by the subkey value. This index allows searching for an attribute value by its prefix. This index allows searching for values within keys.