Chapter 14 – Modeling Cross-Cutting Relationships with Allocations

Publisher Summary This chapter describes how allocation relationships are used to map from one model element to other model elements to support behavioral, structural, and other forms of allocation. Beginning early in systems development, the modeler may need to relate elements in the system model in abstract, preliminary, and sometimes tentative ways. Allocation is a mechanism for relating model elements in a way that provides guidance for the more rigorous relationships that are subsequently developed during model refinement. Additional user-defined constraints can augment the allocation relationship to add the necessary rigor as the design progresses. For example, an allocation of functions (e.g., activities) to components may be done early in the design. As the design progresses, additional constraints are imposed to ensure that the activity inputs, outputs, and controls are explicitly allocated to component interfaces. With appropriate user-defined constraints, allocation can be used to help enforce specific system development methods to ensure the model's integrity. SysML includes several notational options to provide flexibility for representing allocations of model elements across the system model. The options include both graphical and tabular representations, similar to those used for relating requirements.