Aliasing Models for Mobile Objects

Mobile Objects as Mobile Processes

“…Since Obliq is lexically-scoped, we can ignore the aspects of distribution provided that sites do not fail; site failure would allow clients to trivially observe whether an object on one site has moved to another site. Following this idea, we focus on Øjeblik [23], an object-based language that represents Obliq's concurrent core, but can also be seen as a concurrent extension of the Imperative Object Calculus [1]. Øjeblik supports a distribution-free abstraction of migration called surrogation.…”

“…Consequently, Correctness as an equation. In [23], we motivated a precise definition of correctness for object surrogation in Øjeblik. The intuition is that the surrogation of an object must be transparent to the clients of that object.…”

“…Of course this must be done in accordance with the peculiarities of the requests themselves and also with protection and serialisation requirements. In [23], we proposed (among others) a formal configuration-style semantics for Øjeblik that was guided by this intuition. In that paper, we also conjectured that the above safety equation holds in the proposed semantics, but no proof was given.…”

“…In the current paper, we present a π-calculus semantics for Øjeblik corresponding to the semantics proposed in [23]. More precisely, our semantics uses an extension of Localised π [19,18], in short Lπ, a variant of the asynchronous π-calculus [10,3], where, similar to the Join-calculus [6], the recipients of a channel are local to the process that created the channel.…”

“…Lemma 9), we prove the correctness of surrogation for a wide class of Øjeblik-programs. As already pointed out in [23], equation (2) cannot be true for all Øjeblik-programs, due to the inherent possibility of objects to modify their own internal state without any control of when such modifications is performed. The situation is analogous to a program that performs a division by x after having itself in the local scope of x assigned 0 to x.…”