DABACON databases contain element instances. An element instance will be of a specified type. The type of the element determines what attributes it may have. For example, a Box could have attributes XLEN, YLEN, ZLEN and position. In AVEVA E3D™, a Box has many more attributes than this! The database schema defines:

Attributes are of different types. The type of an attribute is relevant when accessing attribute values within a PML expression. For example, the expression (XLEN EQ TRUE) is invalid since XLEN is a real rather than a logical. The types of attribute allowed are:

Reference type attributes are pointers to other elements; for example, from a Nozzle to a Branch. They are also used to reference between databases; for example, from a Design item to its Catalogue representation.

Within AVEVA E3D™, the valid attributes for an element can be output by giving the command Q ATT. As well as the attributes defined in the schema, there are user-defined attributes (UDAs) and pseudo-attributes. Pseudo-attributes are not output by Q ATT. Pseudo-attributes are calculated internally by AVEVA E3D™. For example, at a Flange the user may query the p-point information or the arrive/leave tube length. A full list of pseudo-attributes is provided in the Data Model Reference Manual.

Each element instance has a unique reference number. This number never changes, and can even be preserved when the database is reconfigured, and so it can be used to reference an AVEVA E3D™ element from outside AVEVA E3D™.

There are also ‘User Defined Element Types’ (UDET’s) which allows users to change the schema; for example an administrator can define a :PUMP element as a special case of an EQUIpment, with modified lists of attributes and members. Refer to UDETs in the Database Management Reference Manual for further information.