An Equational Theory for Transactions

Abstract

Transactions are commonly described as being ACID: Allor-nothing, Consistent, Isolated and Durable. However, although these words convey a powerful intuition, the ACID properties have never been given a precise semantics in a way that disentangles each property from the others. Among the benefits of such a semantics would be the ability to trade-off the value of a property against the cost of its implementation. This paper gives a sound equational semantics for the transaction properties. We define three categories of actions, A-actions, I-actions and D-actions, while we view Consistency as an induction rule that enables us to derive system-wide consistency from local consistency. The three kinds of action can be nested, leading to different forms of transactions, each with a well-defined semantics. Conventional transactions are then simply obtained as ADI-actions. From the equational semantics we develop a formal proof principle for transactional programs, from which we derive the induction rule for Consistency.

Transactional Monitors for Concurrent Objects

“…This implementation is closer to the conceptual idea underlying transactional monitors: updates and accesses performed by a thread are tracked within a log, and committed only when serializability of a guarded region's execution is not compromised. However, since applications tend to perform a lot more reads than writes, we decided to use a copy-on-write strategy 6 to reduce the cost of read operations (trading it for a potential loss of precision in detecting serializability violations).…”

“…Black et al [6] present a theory of transactions that specifies atomicity, isolation and durability properties in the form of an equivalence relation on processes. Choithia and Duggan [15] present the pik-calculus and pike-calculus as extensions of the pi-calculus that support abstractions for distributed transactions and optimistic concurrency.…”

A Semantic Framework for Designer Transactions

“…al. [1] and Choithia and Duggan [4]. Choithia and Duggan present an extension of the pi-calculus that supports various abstractions for distributed transactions and optimistic concurrency.…”

Concurrency Combinators for Declarative Synchronization

“…Black et al [3] defined an equation theory of atomic transaction operators, where an operator corresponds to an individual ACID (Atomicity, Consistency, Isolation, and Durability) property. The operators can be composed, giving different semantics to transactions.…”

“…into services, and to express an arbitrary synchronization policy that will constrain the concurrent execution of services at runtime. Our basic synchronization policies include true parallelism, sequentiality, and the combination of these two policies called isolation, which is analogous to the isolation non-interference property known from multithreaded transactions [9,3]. Isolated services can be assumed to execute serially, without interleaved steps of other services, which significantly simplifies both programming and reasoning about program correctness.…”