An abstraction is a relationship that relates two elements or sets of elements that represent the same concept at different levels of abstraction or from different viewpoints.

A dependency is a relationship that signifies that a single or a set of model elements requires other model elements for their specification or implementation.

This means that the complete semantics of the depending elements is either semantically or structurally dependent on the definition of the supplier element(s).

A deployment is the allocation of an artifact or artifact instance to a deployment target. A component deployment is the deployment of one or more artifacts or artifact instances to a deployment target, optionally parameterized by a deployment specification. Examples are executables and configuration files.

A manifestation is the concrete physical rendering of one or more model elements by an artifact.

Realization is a specialized abstraction relationship between two sets of model elements, one representing a specification (the supplier) and the other represents an implementation of the latter (the client). Realization can be used to model stepwise refinement, optimizations, transformations, templates, model synthesis, framework composition, etc.

A substitution is a relationship between two classifiers signifies that the substituting classifier complies with the contract specified by the contract classifier. This implies that instances of the substituting classifier are runtime substitutable where instances of the contract classifier are expected.

A usage is a relationship in which one element requires another element (or set of elements) for its full implementation or operation. A usage is a dependency in which the client requires the presence of the supplier.