This paper argues that caching, atomicity and layering are fundamental to persistent systems, and that the transactional object cache architecture, as an embodiment of these concerns, provides a foundation for high performance persistent system construction. Central to the paper is a description of the semantics of an abstract transactional object cache architecture that supports a wide range of transactional models and is open to a broad spectrum of transactional cache coherency algorithms. The ty of the abstraction is a consequence of its role in facilitating the definition of a transactional interface, which is the key to the practical application of the transactional object cache architecture. The utility of the architectural framework in general, and the interface in particular, is argued for in the context of existing systems and systems currently under construction within that framework.