13,574 research outputs found
Reachability Analysis of Time Basic Petri Nets: a Time Coverage Approach
We introduce a technique for reachability analysis of Time-Basic (TB) Petri
nets, a powerful formalism for real- time systems where time constraints are
expressed as intervals, representing possible transition firing times, whose
bounds are functions of marking's time description. The technique consists of
building a symbolic reachability graph relying on a sort of time coverage, and
overcomes the limitations of the only available analyzer for TB nets, based in
turn on a time-bounded inspection of a (possibly infinite) reachability-tree.
The graph construction algorithm has been automated by a tool-set, briefly
described in the paper together with its main functionality and analysis
capability. A running example is used throughout the paper to sketch the
symbolic graph construction. A use case describing a small real system - that
the running example is an excerpt from - has been employed to benchmark the
technique and the tool-set. The main outcome of this test are also presented in
the paper. Ongoing work, in the perspective of integrating with a
model-checking engine, is shortly discussed.Comment: 8 pages, submitted to conference for publicatio
A 2-Categorical Analysis of Complementary Families, Quantum Key Distribution and the Mean King Problem
This paper explores the use of 2-categorical technology for describing and
reasoning about complex quantum procedures. We give syntactic definitions of a
family of complementary measurements, and of quantum key distribution, and show
that they are equivalent. We then show abstractly that either structure gives a
solution to the Mean King problem, which we also formulate 2-categorically.Comment: In Proceedings QPL 2014, arXiv:1412.810
De-linearizing Linearity: Projective Quantum Axiomatics from Strong Compact Closure
Elaborating on our joint work with Abramsky in quant-ph/0402130 we further
unravel the linear structure of Hilbert spaces into several constituents. Some
prove to be very crucial for particular features of quantum theory while others
obstruct the passage to a formalism which is not saturated with physically
insignificant global phases.
First we show that the bulk of the required linear structure is purely
multiplicative, and arises from the strongly compact closed tensor which,
besides providing a variety of notions such as scalars, trace, unitarity,
self-adjointness and bipartite projectors, also provides Hilbert-Schmidt norm,
Hilbert-Schmidt inner-product, and in particular, the preparation-state
agreement axiom which enables the passage from a formalism of the vector space
kind to a rather projective one, as it was intended in the (in)famous Birkhoff
& von Neumann paper.
Next we consider additive types which distribute over the tensor, from which
measurements can be build, and the correctness proofs of the protocols
discussed in quant-ph/0402130 carry over to the resulting weaker setting. A
full probabilistic calculus is obtained when the trace is moreover linear and
satisfies the \em diagonal axiom, which brings us to a second main result,
characterization of the necessary and sufficient additive structure of a both
qualitatively and quantitatively effective categorical quantum formalism
without redundant global phases. Along the way we show that if in a category a
(additive) monoidal tensor distributes over a strongly compact closed tensor,
then this category is always enriched in commutative monoids.Comment: Essential simplification of the definitions of orthostructure and
ortho-Bornian structure: the key new insights is captured by the definitions
in terms of commutative diagrams on pages 13 and 14, which state that if in a
category a (additive) monoidal tensor distributes over a strongly compact
closed tensor, then this category is always enriched in commutative monoid
Higher-Dimensional Timed Automata
We introduce a new formalism of higher-dimensional timed automata, based on
van Glabbeek's higher-dimensional automata and Alur's timed automata. We prove
that their reachability is PSPACE-complete and can be decided using zone-based
algorithms. We also show how to use tensor products to combat state-space
explosion and how to extend the setting to higher-dimensional hybrid automata
Modelling and controlling traffic behaviour with continuous Petri nets
Traffic systems are discrete systems that can be heavily populated. One way of overcoming the state explosion problem inherent to heavily populated discrete systems is to relax the discrete model. Continuous Petri nets (PN) represent a relaxation of the original discrete Petri nets that leads to a compositional formalism to model traffic behaviour. This paper introduces some new features of continuous Petri nets that are useful to obtain realistic but compact models for traffic systems. Combining these continuous PN models with discrete PN models of traffic lights leads to a hybrid Petri net model that is appropriate for predicting traffic behaviour, and for designing trac light controllers that minimize the total delay of the vehicles in the system
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