Critique of orthogonal persistence

Many researchers are pursuing the goal of providing 'orthogonal persistence'. In an orthogonally persistent system, every language-level object in the system can be referenced by the same mechanisms, regardless of longevity or location, with no exceptions. In this paper, we argue that orthogonal persistence is undesirable. The alternatives to orthogonal persistence include other forms of persistence, where persistence is still orthogonal to type but where there are typically restrictions on what objects can reference what objects. Such systems are often structured around 'fine-grained objects' and 'coarse-grained objects', where coarse-grained objects are used as the units of permissions, locking, transferral and so on. We argue that a design involving coarse-grained objects both helps the programmer organise data and provides much better efficiency.