Non-deterministic computing, heterogeneous transactions and recursive atomicity

Nondeterministic, atomic computing primitives are introduced which are used to construct A-nets for describing transaction models precisely. A-nets and the computing primitives can be applied recursively to describe transactions at arbitrary levels of refinement. The techniques are demonstrated by describing a number of well-known and widely used transaction models, in particular ACID-transactions, distributed transactions with two-phase commit, Sagas, and LU6.2 transactions