Nested Actions in Eos

Persistent and distributed object systems have to cope with chaos resulting of concurrent accesses and failures. This suggests the properties of atomicity, isolation and persistence of eeects. This paper presents the Eos action model which is an interpretation of Moss's model. We focus on Eos's eecient support for nested isolation which upholds an adaptive granule of locking based on complex objects. In particular, we formalize nested isolation based on set and tree theory. This approach leads to an eecient implementation in the context of a distributed single-level store. First measurements showed encouraging performance of Eos that seems to outperform largely existing systems providing nested actions. Finally, we propose a simple criterion to order connicting actions, avoiding false connicts and therefore enhancing parallelism.