Fuzzy ACID properties for self-adaptive composite cloud services execution

The ACID transaction model has played a cornerstone role in service composition to guarantee that composite services (CSs) have transactional support and consistent outcomes even in presence of failures. However, the classical ACID properties are too restrictive for independent and multi-proprietors services running on distributed environments, such clouds. Transactional properties allow a relaxed atomicity and isolation, providing an "all-or-(almost)nothing" model. In previous works, we proposed a model to relax atomicity, called fuzzy atomicity, according user requirements (acceptable fuzzy atomicity). In this article, we extend that model and propose an approach to measure the fuzzy atomicity. Our model allows to self-adapt the CS execution, taking into account the state of the CS execution and user preferences (ie, the acceptable fuzzy atomicity expressed in the user requirements). This fuzzy atomicity measure is applied in a self-adaptive CS execution model based on the transactional properties (pivot, compensatable, and retriable) of its component services and on a checkpointing mechanism. It is suitable to cloud computing, which offers cloud services on demand and in which CS execution should preserve the self-organizing and self-adaptivity properties of such environment, specially in the presence of failures. We show how it is possible to relax the retriable property in CSs execution, based on our fuzzy atomicity model. Additionally, in this work, we present a comparative analysis of the most recent works in the context of ACID properties relaxation for CS.