Guaranteeing Resource Bounds for Component Software

Abstract

Abstract. Component software is software that has been assembled from various pieces of standardized, reusable computer programs, socalled components. Executing component software creates instances of these components. For several reasons, for example, limited resources and/or application requirements, it can be important to have control over the number of such instances. In the previous work [3], we have given an abstract component language and a type system which ensures that the number of simultaneously active instances of any component never exceeds a sharp bound expressed in the type. The language featured instantiation and reuse of components, as well as sequential composition, choice and scope. This work extends the previous one to include a parallel composition. Moreover, we improve on the operational semantics by using a small-step reduction relation. As a result, we can prove the soundness property of our static type system using the technique of Wright and Felleisen.

Finding Resource Bounds in the Presence of Explicit Deallocation

“…We present a small component language and develop a type system which can statically prevent this type of errors . This work continues our previous works [3,18] by including explicit deallocation. We prove that the type system is sound with respect to safe deallocation and that sharp resource bounds can be computed statically.…”

“…Suppose X is the type of an expression E. Then X i is the upper bound of the number of simultaneously active instances for all components during the execution of E. Multisets are the right data structure to store this information. Next, X o is the maximum number of instances that 'survive' at the end of the execution when executing E alone, as in [3,18]. In this paper, we have the deallocation primitive and its behaviour is opposite to instantiation so we use signed multisets.…”

“…This work follows a more liberal approach compared to our previous works [3,18] where the resource bounds, i.e. the maximum number of instances for each component, are known in advance and the type system checks these bounds in typing rules.…”

“…In the previous work [3,18], the main features are instantiation and reuse, sequential composition, choice, parallel composition and scope and the deallocation of instances is controlled by scope mechanism. In this work, we consider sequencing and parallel composition, choice and scope, add an explicit deallocation primitive, which allows us to imperatively remove an instance in the same scope.…”

Stayin' alert:

“…Even in situations where resource requirements are known in advance and guaranteed to be available, exceptional situations may occur, as none of the mainstream languages support resource-aware type systems [31].…”