FM3 or Fame meta-metamodel is a model to describe metamodels.

• FM3 is self-described in itself.
• FM3 is a superset of a subset of EMOF.
• FM3 is small and simple.
• FM3 is extendable.

FM3 applies lessons learned and best practices from using EMOF in the Moose and Famix project:

• FM3 allows packages to weave methods into existing classes of other packages. Using this, Famix extensions may extend the core specification of the model.
• FM3 is EMOF reduced to the max. We removed anything that was not used by Famix. For example, EMOF specifies multiplicity of properties using lower: Integer and upper: Unlimited. As upper may possibly be unlimited, EMOF even introduces Unlimited as core primitive type, messing up any implementation. Analysis of existing models showed however that we use 0..1 and 0..* only! Hence, FM3 models multiplicity of properties using multivalued: Boolean, simple and no need for fancy primitives.

See also:

• MSE

FM3.Element

is an abstract class with attributes

• Element owner (derived)
• String fullName (derived)
• String name

with these constraints

• name must be alphanumeric
• fullName is dervied recursively, concatenating owner.fullName and name
• fullName is seperated by dots, eg FAMIX.Class.allAttributes

FM3.Class

subclasses NamedElement with attributes

• Boolean abstract
• Boolean primitive (derived)
• Boolean root (derived)
• Class superclass
• Package package (container, opposite Package.classes)
• Property allAttributes (derived, multivalued)
• Property attributes (multivalued, opposite Property.class)

with these reserved instances

 OBJECT := (FM3.Class (name 'Object') (root true))
 BOOLEAN := (FM3.Class (name 'Boolean') (primitive true) (superclass (ref: Object)))
 NUMBER := (FM3.Class (name 'Number') (primitive true) (superclass (ref: Object)))
 STRING := (FM3.Class (name 'String') (primitive true) (superclass (ref: Object)))

for any other instance of MF3.Class, these constraints apply

• owner is derived from package
• superclass is not nil
• superclass must not be a primitive
• superclass chain may not include cycles
• package must not be nil
• allAttributes is derived as union of attributes and superclass.allAttributes
• only one of allAttributes may have container = true
• allAttributes must have unique names
• in particular, none of attributes may have the name of any of superclass.allAttributes

// TODO, I am not sure about this ... it does not allow overloading of attributes, does anyone need overloading?

FM3.Package

subclasses NamedElement with attributes

• Class classes (multivalued, opposite Class.package)
• Property extensions (multivalued, opposite Property.package)

with these constraints

• owner is nil
• classes must have unique names
• for each element of extentions, it class is not in classes

FM3.Property

subclasses NamedElement with attributes

• Boolean composite (derived)
• Boolean container
• Boolean derived
• Boolean multivalued
• Class class (container, opposite Class.attributes)
• Class type
• Package package (opposite Package.extensions)
• Property opposite (opposite Property.opposite)

with these constraints

• owner is derived from class
• composite is derived from opposite.container
• container implies not multivalued
• if set, opposite.opposite must be self
• if set, opposite.class must be type
• class must not be nil
• type must not be nil

and these semantics

• container property chains may not include cycles
• opposite properties must refer to each other
• any multivalued property defaults to empty
• boolean properties default to false
• non primitive properties default to null
• string and number properties not have a default value // TODO is this wise?