UCM — create an abstract class IItemBinding

Ports of component types contain an IPortSpec, which is an abstract class that contains nothing, thus allowing future meta-model extensions without any restriction regarding the way ports are specified.
On the other hand, class ConnectorDefinition contains ItemBinding, which explicitly associates an InteractionItem with an ITypeDeclaration. Although this will cover most situations, it is not as general as for component ports, since it implies that connector definitions depend on the notion of data type.
There should be an intermediate abstract class IItemBinding that only contains InteractionItem, and that is extended by class ItemBinding.

create class IItemBinding

Create an abstract class named IItemBinding with the following field:

• interactionItem: InteractionItem [1]

Class ItemBinding will inherit class IItemBinding. Field itemBinding of class ConnectorDefinition will now reference IItemBinding.