  The increasing development of cyber-physical systems (CPSs) requires
modellers to represent and reason about physical values. This paper addresses
two major, inter-related, aspects that arise when modelling physical measures.
Firstly, there is often a heterogeneity of representation; for example: speed
can be represented in many different units (mph, kph, mps, etc. . . ).
Secondly, there is incoherence in composition; for example: adding a speed to a
temperature would provide a meaningless result in the physical world, even
though such a purely mathematical operation is meaningful in the abstract.
These aspects are problematic when implicit semantics - concerned with
measurements - in CPSs are not explicit (enough) in the requirements, design
and implementation models. We present an engineering approach for explicitly
modelling measurements during all phases of formal system development. We
illustrate this by moving from Event-B models to Java implementations, via
object oriented design.
