The following terms are used throughout the EDMassist
| Term | Description |
| Application data | A data item with values that provide information of interest to application software referencing it. |
| Complex entities | A complex entity denotes an implicitly or explicitly declared entity data type that is part of a supertype and subtype network. |
| Data | A computational unit with its content representing a piece of information. |
| Data type | An identifier denoting the class to which a data belongs. |
| Database | A concrete realization of a repository by means of a database engine, such as EDMdatabase |
| Dictionary data | A data item with values representing information about the structure and behavior of another data instance. |
| Entity | An entity denotes something that exists in the real world and information about it is of interest to its viewer. |
| ENTITY data type | An EXPRESS language construct that is used to describe structures of a data type in terms of attributes and local rules. |
| ENTITY instance | An instance of the EXPRESS ENTITY data type that exist in a database. |
| EXPRESS | The formal name of a data definition language. It is used to describe the information requirement of a domain such as STEP Application Protocols, Generic Resources and some aspects of Implementation Methods. A description of the EXPRESS language is set out in Part 11 of STEP (ISO 10303-11). |
| Global rule | An EXPRESS language construct using the keyword RULE to define constraint that applies to one or more instances of an ENTITY Data type or ENTITY Data types. |
| Information | An abstract thing providing knowledge (facts, concepts, instructions etc.) about an entity. |
| Language binding | A specification of the SDAI in a particular programming language. |
| Local rule | A class of EXPRESS RULE construct used to define the uniqueness and domain constraint of the EXPRESS ENTITY data type. |
| Model | A virtual container within which related data items exists. |
| Repository | A logical data storage that is identifiable by name alone. |
| Schema | An EXPRESS language construct, which is used to denote a collection of related data types. |
| Session | The period when the facilities of the EXPRESS Data Manager are active for a client. |
| TYPE data type | An EXPRESS Language construct that is used to create defined data types and declares an identifier to refer to it. |