In my post-graduate research and subsequent career in operational analysis, the difference between following seems to have become clearer with the years: (1) a model of a problem or operations in the real world and (2) implementation of a corresponding analysis tool that applies the model to actual data.
Item (1) can take many forms: A collection of inter-related equations, a schematic, and/or a word description. But one cannot take item (1) and apply it to actual data to get the results.
To apply a model to actual data, the model must be realized via item (2), which can take the form of spreadsheets, coding (preferably in a 4th generation language), software whose execution is specified via a graphical schematic language , digital circuit/systems modelling environments , discrete event simulators, optimization packages, etc.
Is there an actual paper, book, or some preferably non-contentious source that describes this distinction? Some of what I've found seem not to distinguish between the two items, preferring instead to distinguish their amalgamation from "implementation" of recommendations falling out of the analysis. The latter is not what I mean by "implementation" in the context of this question.
 Core Sim, G2 ReThink, LabView, etc.
 These may use a combination of schematics and text languages for specifying system behaviour.