We propose a technique for synthesizing switching guards for hybrid systems to satisfy a given state-based safety constraint. Using techniques from sum of squares (SOS) optimization, we design guards defined by semialgebraic sets that trigger mode switches, and we guarantee that the synthesized switching policy does not allow Zeno executions. We demonstrate our approach on an example of switche...

It is shown that in any polygonal art gallery of n sides it is possible to place bn/3c point guards whose range of vision is 180◦ so that every interior point of the gallery can be seen by at least one of them. The guards can be stationed at any point of the art gallery. This settles an open problem posed by J. Urrutia.  2000 Elsevier Science B.V. All rights reserved.

Suppose that you are competing in a two-player game in which you and your opponent attempt to pack as many “prisoners” as possible on the squares of an n×n checkerboard; each prisoner has to be “protected” by an appropriate number of guards. Initially, the board is covered entirely with guards. The players – designated as “red” and “blue” – take turns adjusting the board configuration using one...

Timed automata constitute a well adapted model for real-time aspects. However, a classical forward analysis algorithm used to verify safety properties has been showed to be incorrect in the general framework of timed automata. Nevertheless, it is correct when we restrict the class to timed automata with only non-diagonal guards. The aim of this work is to understand the role of diagonal guards ...

For ML and Haskell, accurate warnings when a function definition has redundant or missing patterns are mission critical. But today’s compilers generate bogus warnings when the programmer uses guards (even simple ones), GADTs, pattern guards, or view patterns. We give the first algorithm that handles all these cases in a single, uniform framework, together with an implementation in GHC, and evid...

This paper presents findings from the British Broadcasting Corporation (BBC) prison study - an experimental case study that examined the consequences of randomly dividing men into groups of prisoners and guards within a specially constructed institution over a period of 8 days. Unlike the prisoners, the guards failed to identify with their role. This made the guards reluctant to impose their au...

Most information systems that are driven by process models (e.g., workflow management systems) record events in event logs, also known as transaction logs or audit trails. We consider processes that not only keep track of their history in a log, but also make decisions based on this log. To model such processes we extend the basic Petri net framework with the notion of history and add guards to...

We study the problem of placing guard towers on a terrain such that the terrain can be seen from at least one tower. This problem is important in many applications, and has an extensive history in the literature (known as, e.g., multiple observer siting). In this paper, we consider the problem on polyhedral terrains, and we allow the guards to see only a fixed fraction of the terrain, rather th...