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A Meta-model of EXPRESS in UML for MOF

andUML to EXPRESS

David PriceApril 2002

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Purpose

• This model is not a standard, just an example• An introduction to EXPRESS

– Shows the major EXPRESS constructs

• Uses a style similar to that of the meta-model of UML

• Serves as sample model for UML/XMI to EXPRESS stylesheets (tested on ArgoUML XMI files)

• At some point, a model like this built in MOF would enable direct use of XMI by EXPRESS– Currently, EXPRESS must be translated into UML via the

ISO 10303-25 EXPRESS to XMI Bindings standard that is out for ballot in ISO TC 184/SC4 Industrial Data

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Schemas define a Namespace

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Schemas can share declarations

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Instances are of Entity Types

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Entity and Attribute may be Specialized

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Types are domains

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Aggregate and Primitive Types

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Rules and Constants

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Algorithms and Expressions

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Next Steps

• Testing– Convert this UML model to a MOF model

• MOF uses a subset of UML– I think this model only uses that subset but this needs to

be confirmed• Using MOF, a better analysis comparing UML and

EXPRESS can be done• Enables MOF repository access to EXPRESS schemas

– MOF is a standard for access to models/schemas– There are implementations of this

• Using XMI four layer architecture, Entity Instances can be exchanged in a very late bound XML document

• Standardization in ISO? OMG?• Develop two-way EXPRESS/UML mapping

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A Bit on UML to EXPRESS

• Testing a mapping via XSLT– Not a standard yet, ISO 10303-25 only does EXPRESS to UML

• Small subset of UML is supported – mapping summary:– UML Class -> ENTITY– UML Abstract Class -> ABSTRACT SUPERTYPE

• no other SUPERTYPE constraint created

– UML Generalization -> SUBTYPE OF, Multiple inheritance is supported

– UML Attribute (single valued) -> explicit attribute– UML string and UML Class string -> STRING simple type– UML boolean and UML Class boolean -> BOOLEAN simple type– UML int and UML Class integer -> INTEGER simple type– UML Class real -> REAL simple type

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A Bit on UML to EXPRESS(2)

• The mapping summary continued– UML Association between Classes -> explicit attribute in

two cases• 1 - one end name = association name > explicit attribute at

end with no, or different name• 2 - existence dependence -> explicit attribute at end with

dependency (i.e. lower bound is 0)– Assoc End 1 lower bound zero and Assoc End 2 lower bound not

zero means Class 1 depends on Class 2• SET is created for upper bound > 1• if multiplicity is 0..1 then OPTIONAL is included• if both association end lower bounds are 0 nothing is created

except as in 1 above– this is because cannot tell which entity should own the attribute

• if both association end lower bounds are not zero nothing is created except as in 1 above

• no inverses are created