  Non-volatile memory (NVM), also known as persistent memory, is an emerging
paradigm for memory that preserves its contents even after power loss. NVM is
widely expected to become ubiquitous, and hardware architectures are already
providing support for NVM programming. This has stimulated interest in the
design of novel concepts ensuring correctness of concurrent programming
abstractions in the face of persistency and in the development of associated
verification approaches.
  Software transactional memory (STM) is a key programming abstraction that
supports concurrent access to shared state. In a fashion similar to
linearizability as the correctness condition for concurrent data structures,
there is an established notion of correctness for STMs known as opacity. We
have recently proposed durable opacity as the natural extension of opacity to a
setting with non-volatile memory. Together with this novel correctness
condition, we designed a verification technique based on refinement. In this
paper, we extend this work in two directions. First, we develop a durably
opaque version of NOrec (no ownership records), an existing STM algorithm
proven to be opaque. Second, we modularise our existing verification approach
by separating the proof of durability of memory accesses from the proof of
opacity. For NOrec, this allows us to re-use an existing opacity proof and
complement it with a proof of the durability of accesses to shared state.
