Expressing and Computing Passage Time Measures of GSPN Models with HASL

Abstract

Abstract. Passage time measures specification and computation for Generalized Stochastic Petri Net models have been faced in the literature from different points of view. In particular three aspects have been developed: (1) how to select a specific token (called the tagged token) and measure the distribution of the time employed from an entry to an exit point in a subnet; (2) how to specify in a flexible way any condition on the paths of interest to be measured, (3) how to efficiently compute the required distribution. In this paper we focus on the last two points: the specification and computation of complex passage time measures in (Tagged) GSPNs using the Hybrid Automata Stochastic Logic (HASL) and the statistical model checker COSMOS. By considering GSPN models of two different systems (a flexible manufacturing system and a workflow), we identify a number of relevant performance measures (mainly passage-time distributions), formally express them in HASL terms and assess them by means of simulation in the COSMOS tool. The interest from the measures specification point of view is provided by the possibility of setting one or more timers along the paths, and setting the conditions for the paths selection, based on the measured values of such timers. With respect to other specification languages allowing to use timers in the specification of performance measures, HASL provides timers suspension, reactivation, and rate change along a path.

Improving and Assessing the Efficiency of the MC4CSLTA Model Checker

“…The probabilities computed with MC4CSL TA are in accordance with that computed with Cosmos available in [22]. The comparison with Cosmos, on this and on other models, proved to be very useful in detecting errors in MC4CSL…”

Expressiveness and Conciseness of Timed Automata for the Verification of Stochastic Models

“…Automata with time constraints have been used to specify path-based performance indices [16] for Stochastic Activity Networks [15], while hybrid automata have been used to define rather complex forms of passage of time [2] for GSPN, as well as generic performance properties [9] that are estimated using simulation. The use of a Deterministic Timed Automaton (DTA) in the stochastic logic CSL TA [12] allows to specify paths in terms of state propositions and action names associated to CTMC states and transitions (respectively) and in terms of the timed behaviour of portions of the paths.…”

HASL: A new approach for performance evaluation and model checking from concepts to experimentation

“…This is useful for eliminating the effect of the initial transient from long run measures as already discussed in[4] 9. the choice of beginning measuring in low is arbitrary, equivalently Aper can be defined so that analysis starts in either mid or high 10.…”