TABLE OF CONTENTS This chapter describes SysML support for modeling constraints on the performance and physical properties of systems and their environment to support a wide array of engineering analyses.
A typical design effort includes the need to perform many different types of engineering analyses to support trade-off studies, sensitivity analysis, and design optimization. It may include the analysis of performance, reliability, and physical properties to name a few. SysML supports this type of analysis through the use of parametric models.
Parametric models capture the constraints on the properties of the system, which can then be evaluated by an appropriate analysis tool. The constraints are expressed as equations whose parameters are bound to the properties of a system. Each parametric model can capture a particular engineering analysis of the design. Multiple engineering analyses can then be performed on each design alternative to support trade-off analysis.
SysML introduces a constraint block to support the construction of parametric models. A constraint block is a special kind of block used to define equations so that they can be reused and interconnected. Constraint blocks have two main features: a set of parameters and an expression that constrains the parameters. Constraint blocks follow a similar pattern of definition and use that applies to blocks and parts as described in Chapter 6. A use of a constraint block is called a constraint property. The definition and use of constraint blocks is represented on a block definition diagram and parametric diagram, respectively.
