Despite the ubiquity of XML, research in metrics for XML documents is scarce. This paper proposes and discusses eleven metrics to measure the quality and complexity of XML Schema and conforming XML documents. To provide an easy view of these metrics, two composite indices have been defined to measure quality and complexity. An open source metric analyzer… (More)
Codd proposed the use of two interpretations of nulls to handle missing information in relational databases that may lead to a 4-valued logic [Codd86, Codd87]. In a more general model, three interpretations of nulls are necessary [Roth, Zani]. Without simplification, this may lead to a 7-valued logic, which is too complicated to be adopted in relational… (More)
The priority ceiling protocol (PCP) is an effective protocol for minimizing priority inversions in real-time scheduling. Priority inversion occw-s when a high priority task is blocked by a low priority task, such as at a shared semaphore or a protected operation. PCP guarantees the absence of chained priority inversion or deadlock. The ceiling locking (CL)… (More)
Although some specific mutual exclusion problems have been studied extensively, automatic solutions to synchronize general mutual exclusion problems with arbitrary mutual exclusion constraints have not been fully explored. This paper discusses an Ada 83 solution that can be applied to any general mutual exclusion problem. This solution is based on strong… (More)
We describe a formalism that maps a first order logic-based specification into a graph representation (Influence Graph). The graph can be shown to be a representation scheme equivalent to ordinary Petri nets, with an emphasis on general causal implications instead of resource usage. By making the procedural aspects of a system explicit, the graph helps… (More)
The new protected type and requeue features in Ada-94 make possible the efficient implementations of many concurrent solutions, previously not possible in Ada-83. In this paper, the implementations of various semaphore systems in Ada-94 are presented. These systems are more general and powerful than the familiar binary and counting semaphores. As examples,… (More)
Several articles have appeared in SIGART Newsletter on the game of Mastermind during the recent three to four years (1 - 8). In particular, P. Norvig described a heuristic for obtaining an approximation to the optimal solution(1). In this article, several simple heuristics to play Mastermind are analyzed.