Scoped types for real-time Java

A memory model based on scoped areas is one of the distinctive features of the Real-Time Specification for Java (RTSJ). Scoped types ensure timely reclamation of memory and predictable performance. The price to pay for these benefits is an unfamiliar programming model that, at the same time, is complex, requires checking all memory accesses, and rewards design-time errors with run-time crashes. We investigate an alternative approach, referred to as scoped types, that simplifies the task of managing memory in real-time codes. The key feature of our proposal is that the run-time partition of memory imposed by scoped areas is straightforwardly mirrored in the program text. Thus cursory inspection of a program reveals which objects inhabit the different scopes, significantly simplifying the task of understanding real-time Java programs. Moreover, we introduce a type system which ensures that no run-time errors due to memory access checks occur. Thus a RTSJ-compliant virtual machine does not require memory access checks. The contributions of this paper are the concept of scoped types, and a proof soundness of the type system. Experimental results are described in future work.