|The paper presents how domain modeling may leverage the hierarchical composition, supporting two orthogonal mechanisms (vertical and horizontal) for composing completely autonomous parts. The vertical mechanism is in charge of coordinating heterogeneous components, tools or services at a high level of abstraction, by hiding the technical details. The result of such a composition is called “domain” and represents a high granularity unit of reuse, which may be easily developed in Mélusine framework. A domain is characterised by a Domain Specific Language (DSL) and applications in that domain are defined by models executed by the DSL interpreter. Most often, this is significantly simpler than writing a program using a general purpose language. Unfortunately, DSLs have a narrow scope, while real world applications usually span over many domains, raising the issue of domain (and DSL) composition. To overcome this problem, the horizontal mechanism composes domains at the level of their DSLs, even if they have been independently designed and implemented. The paper presents a model and metamodel perspective of the Mélusine bi-dimensional composition, assisted and automated with the Codele tool, which allows specification at a high level of abstraction, followed by Java and AspectJ code generation.