Specifications can be reused from one model to another. This is because they are not tied to particular cells and columns. In conventional development, the pogrammer can cut and paste code from one worksheet to use in another, but will need to check and alter any absolute cell references it contains.
Also, MM's inheritance mechanism (described below) means the programmer can build up libraries of partially-specified objects and systems and subsequently include them in a variety of different models. We regard this as one of MM's most innovative features. An important point here is that the compiler can check each specification for errors as soon as it has been written, before it is used in the program that calls it.