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1. Atom. An attribute defined by a type which contains only one slot implicitly named “value”. (Atomic types are also called primitive types and are pre-defined by the system. For example, Number is an atomic type. All atomic types inherits from the type "Atom".) TQLEngine A-Stack currently does not support user-defined atomic types.
2. Composite. An attribute defined by a type which is a container (contains more than one slot). A container type can be defined by the user using type definition language (<Def/>)
3. Ad-hoc Inline composite. An attribute which is a container defined only at the time of model definition, that is, no such type is pre-defined. Therefore, the structure of ad-hoc inline composite cannot be reused by other models, but only exist in the particular model itself. All Ad-hoc composite inline composites must be declared with the type "Data".
4. Cherry-picked. Cherry-picked attributes are declared using the type "Attribute"picking allows to create a structure with a subset of model attributes. For details see CherryPicking.