[FOM] A simplification of Structure Theory.

[Patrik Eklund]

Would just like to draw your attention not to confuse 'structure theory' 
in that sense with what was coined by Werner Gähler around 1980 
concerning "A topological approach to structure theory" (Math Nachr 100 
(1981), 93-144).

It's a categorical approach, and now decades later we have used monads, 
and composition of monads, for describing the benefit of having formal 
constructions of signatures, terms 
(http://www.sciencedirect.com/science/article/pii/S0165011413000997, 
http://www.sciencedirect.com/science/article/pii/S0165011415003152) and 
sentences in extensions related to Burstall-Goguen's (institutions) and 
Meseguer's (entailment system) approaches to logic.

Our new way to handle type constructors is fundamental in these 
respects, e.g., for the foundations of lambda-calculus.

Patrik