A CommonScope that is also a LocalScope, or equivalently, a CommonScope that is not a Schema. 

a NamedElement (EXPRESS model element) that can be defined in either a Schema or a LocalScope, and has (or may have) a unique identifier within that Scope. 

A Scope in which CommonElements can be declared. 

A ScopedId whose namespace is the LocalScope in which it is declared. 

A Scope that is neither a SCHEMA nor a NamedType. 

a principal concept of the EXPRESS language, an object that is defined in a model, has a notion of "lifetime", and has an identifier that refers to it in Schemas or in some nested Scope in a Schema. 

represents the collection of all entity instances (instances of NamedTypes?) over which the LocalRules and GlobalRules of a schema are to be evaluated 

a Scope that represents an EXPRESS SCHEMA, i.e. 

a NamedElement whose scope is a Schema, an independent model element. 

a ScopedId whose namespace is the Schema in which it is declared. 

any EXPRESS object that defines a namespace for the interpretation of identifiers. 

An abstract type representing the combination of an Identifier and its namespace, which together constitute a well-defined symbol for an EXPRESS ModelElement. 

represents the EXPRESS "interface" relationships (USE, REFERENCE) between an interfacing Schema and the SchemaElements that it interfaces from the Schema in which they are defined.