What you defined is not market microstructure, but the platonic ideal of a matching engine. The microstructure of a market is defined (by a Wikipedia source) as: "the study of the process and outcomes of exchanging assets under a specific set of rules. While much of economics abstracts from the mechanics of trading, microstructure theory focuses on how specific trading mechanisms affect the price formation process.”[0]

That is fantastically complicated. As you say, anyone can write a matching engine.

[0] http://en.wikipedia.org/wiki/Market_microstructure