From:  http://www.steptools.com/mail-archive/wg10/bin00002.bin
See: http://www.steptools.com/mail-archive/wg10/msg00032.html

(*                                  Annex C

                               (informative)

           EXPRESS representation of the UML Physical Metamodel

Following is an EXPRESS schema that represents the relevant portions of the
UML Physical Metamodel as specified in UML 1.3 Section 6.2. This is the
metamodel upon which the UML DTD for XMI is based.
*)
(* An EXPRESS representation of portions of the UML Physical Metamodel *)
(* specified in UML 1.3 Section 6.2 *)
(*
Note that several EXPRESS identifiers are prefixed with the string uml.
Those identifiers required a change in name as the name in the UML
meta-model
is an EXPRESS reserved word.
*)

SCHEMA part25_representation_of_uml_physical_metamodel;

TYPE AggregationKind = ENUMERATION OF ( none, uml_aggregate, composite );
END_TYPE;

TYPE CallConcurrencyKind = ENUMERATION OF ( sequential, quarded,
concurrent);
END_TYPE;

TYPE ChangeableKind = ENUMERATION OF ( changeable, frozen, addOnly);
END_TYPE;

TYPE Name = STRING;
END_TYPE;

TYPE OrderingKind = ENUMERATION OF ( unordered, ordered, sorted );
END_TYPE;

TYPE ParameterDirectionKind = ENUMERATION OF ( out );
END_TYPE;

TYPE ScopeKind = ENUMERATION OF ( instance, uml_classifier);
END_TYPE;

TYPE VisibilityKind = ENUMERATION OF ( public, protected, private);
END_TYPE;

ENTITY Association
SUPERTYPE OF ( ONEOF ( AssociationClass) )
SUBTYPE OF ( Relationship, GeneralizableElement );
connection : LIST[2:?] OF AssociationEnd;
END_ENTITY;

ENTITY AssociationEnd
SUBTYPE OF ( ModelElement );
isNavigable : BOOLEAN;
ordering : OrderingKind;
aggregation : AggregationKind;
targeScope : ScopeKind;
multiplicity : Multiplicity;
changeability : ChangeableKind;
uml_type : Classifier;
(* specification association omitted for Part 25 use *)
END_ENTITY;

ENTITY AssociationClass
SUBTYPE OF ( Association, Class) ;
END_ENTITY;

ENTITY Attribute
SUBTYPE OF (StructuralFeature);
(* initialValue attribute omitted for Part 25 use *)
END_ENTITY;

ENTITY BehavioralFeature
ABSTRACT SUPERTYPE OF (ONEOF(Operation) )
SUBTYPE OF (Feature);
isQuery : BOOLEAN;
END_ENTITY;

ENTITY Class
SUPERTYPE OF ( ONEOF ( AssociationClass) )
SUBTYPE OF ( Classifier );
isActive : BOOLEAN;
END_ENTITY;

ENTITY Classifier
ABSTRACT SUPERTYPE OF (ONEOF ( Class, DataType ))
SUBTYPE OF (GeneralizableElement, Namespace);
END_ENTITY;

ENTITY DataType
SUBTYPE OF ( Classifier );
END_ENTITY;

ENTITY Element
ABSTRACT SUPERTYPE OF (ONEOF(ModelElement));
END_ENTITY;

ENTITY ElementImport;
visibility : VisibilityKind;
uml_alias : Name;
modelElement : ModelElement;
package : Package;
END_ENTITY;

ENTITY ElementOwnership;
visibility : VisibilityKind;
isSpecification : BOOLEAN;
ownedElement : ModelElement;
namespace : Namespace;
END_ENTITY;

ENTITY Feature
ABSTRACT SUPERTYPE OF (ONEOF (StructuralFeature, BehavioralFeature))
SUBTYPE OF (ModelElement);
ownerScope : ScopeKind;
owner : Classifier;
END_ENTITY;

ENTITY GeneralizableElement
ABSTRACT SUPERTYPE OF (ONEOF ( Classifier, Association) )
SUBTYPE OF (ModelElement);
isRoot : BOOLEAN;
isLeaf : BOOLEAN;
isAbstract : BOOLEAN;
END_ENTITY;

ENTITY Generalization
SUBTYPE OF ( Relationship );
discriminator : Name;
parent : GeneralizableElement;
child : GeneralizableElement;
(* powertype association omitted for Part 25 use *)
END_ENTITY;

ENTITY ModelElement
ABSTRACT SUPERTYPE OF (ONEOF(Feature, Namespace, GeneralizableElement,
Parameter, AssociationEnd, Relationship))
SUBTYPE OF (Element);
name : Name;
visibility : VisibilityKind;
isSpecification : BOOLEAN;
namespace : Namespace;
END_ENTITY;

ENTITY Multiplicity;
range : MultiplicityRange;
END_ENTITY;

ENTITY MultiplicityRange;
lower : INTEGER;
upper : INTEGER;
END_ENTITY;

ENTITY Namespace
ABSTRACT SUPERTYPE OF ( ONEOF( Classifier , Package) )
SUBTYPE OF (ModelElement);
END_ENTITY;

ENTITY Operation
SUBTYPE OF (BehavioralFeature);
concurrency : CallConcurrencyKind;
isRoot : BOOLEAN;
isLeaf : BOOLEAN;
isAbstract : BOOLEAN;
specification : STRING;
(* method association omitted for Part 25 use *)
END_ENTITY;

ENTITY Package
SUPERTYPE OF ( ONEOF ( uml_Model ))
SUBTYPE OF ( Namespace, GeneralizableElement );
END_ENTITY;

ENTITY Parameter
SUBTYPE OF (ModelElement);
uml_type : Classifier;
kind : ParameterDirectionKind;
(* defaultValue attribute omitted in Part 25 use *)
behavioralFeature : BehavioralFeature;
END_ENTITY;

ENTITY Relationship
ABSTRACT SUPERTYPE OF ( ONEOF (Generalization, Association))
SUBTYPE OF ( ModelElement );
END_ENTITY;

ENTITY StructuralFeature
ABSTRACT SUPERTYPE OF (ONEOF (Attribute))
SUBTYPE OF (Feature);
multiplicity : Multiplicity;
changeability : ChangeableKind;
targetScope : ScopeKind;
uml_type : Classifier;
END_ENTITY;

ENTITY uml_Model
SUBTYPE OF ( Package );
END_ENTITY;

END_SCHEMA;