Mechanism of operation vs. system model
Most often in the course of analysis we use the term model, less often mechanism. The thing is that the term mechanism appears when we want to explain something, e.g. “the mechanism of generating a discount on an invoice”. The thing is that the term mechanism appears when we want to explain something, e.g. “the mechanism for generating a discount on an invoice”. But here beware! A model (block diagrams, formulae, etc.) is documentation, a copyrighted description. The mechanism is what we understood by reading these documentation (model), because the mechanism is protected know-how. The content of the application to the Patent Office is the model (description), but what we patent is the mechanism invented/developed.
Source: Mechanism of operation vs. system model – Jarosław Żeliński IT-Consulting