The Theory of Matrices. By F R. Gantmacher. Two volumes, pp. 374 and 276. 1959. (Translated from the Russian by K. A. Hirsch; Chelsea Publishing Company, New York)

Will Tracz, our esteemed editor and Used-Program salesman, has written an entertaining, non-technical book dealing with the practice (and lack of) of software reuse. Its a collection of essays, mostly rehashed (reused?) and updated from various columns and papers published over the years.. Its a short (a bit over 200 pages) easy reading and enjoyable book (I read most of it in one sitting). Some of the essays discuss what was printed in the past and a discussion of the current status of the points.

Safeware: System Safety and Computers

Thiopurine methyltransferase (TPMT) activity exhibits monogenic co-dominant inheritance, with ethnic differences in the frequency of occurrence of variant alleles. With conventional thiopurine doses, homozygous TPMT-deficient patients (~1 in 178 to 1 in 3,736 individuals with two nonfunctional TPMT alleles) experience severe myelosuppression, 30-60% of individuals who are heterozygotes (~3-14% of the population) show moderate toxicity, and homozygous wild-type individuals (~86-97% of the population) show lower active thioguanine nucleolides and less myelosuppression. We provide dosing recommendations (updates at http://www.pharmgkb.org) for azathioprine, mercaptopurine (MP), and thioguanine based on TPMT genotype.

https://ascpt.onlinelibrary.wiley.com/doi/epdf/10.1038/clpt.2010.320

Clinical Pharmacogenetics Implementation Consortium guidelines for thiopurine methyltransferase genotype and thiopurine dosing.

Decentralized supervisory control is investigated by considering problem formulations that model systems whose specifications are given as global constraints, but whose solution is described by local controllers. A necessary and sufficient condition is given for the existence of a solution to the problem of finding decentralized supervisors that ensure that the behavior of the closed-loop system lies in a given range. Where the range of behavior can be described by regular languages, it can be effectively tested whether the decentralized control problem is solvable; in this case, a procedure is given to compute the associated supervisors. >

Think globally, act locally: decentralized supervisory control

Decentralized supervisory control is investigated by considering problem formulations that model systems whose specifications are given as global constraints but whose solution is described by local controllers. A necessary and sufficient condition is given for the existence of a solution to the problem of finding decentralized supervisors that ensure that the behaviour of the closed-loop system lies in a given range. Where the range of behaviour can be described by regular languages, it can be effectively tested whether the decentralized control problem is solvable; in this case, a procedure is given to compute the associated supervisors.

Think Globally, Act Locally: Decentralized Supervisory Control

Introduction.- TCT: General Information.- Chapter 1. Algebraic Preliminaries.- Chapter 2. Linguistic Preliminaries.- Chapter 3. Supervision of Discrete-Event Systems: Basics.- Chapter 4. Decentralized and Distributed Supervision of Discrete-Event Systems.- Chapter 5. Hierarchical Supervision of Discrete-Event Systems.- Chapter 6. Supervisory Control With Partial Observations.- Chapter 7. State-Based Control of Discrete-Event Systems.- Chapter 8. Supervision of Vector Discrete-Event Systems.- Chapter 9. Supervisory Control of Timed Discrete-Event Systems.- Bibliography.- Appendix: Supervisory Control of a Mine Pump.- Index.

Supervisory Control of Discrete-Event Systems

In the supervisory control of discrete-event systems based on controllable languages, a standard way to handle state explosion in large systems is by modular supervision: either horizontal (decentralized) or vertical (hierarchical). However, unless all the relevant languages are prefix-closed, a well-known potential hazard with modularity is that of conflict. In decentralized control, modular supervisors that are individually nonblocking for the plant may nevertheless produce blocking, or even deadlock, when operating on-line concurrently. Similarly, a high-level hierarchical supervisor that predicts nonblocking at its aggregated level of abstraction may inadvertently admit blocking in a low-level implementation. In two previous papers, the authors showed that nonblocking hierarchical control can be guaranteed provided high-level aggregation is sufficiently fine; the appropriate conditions were formalized in terms of ’control structures‘ and ’observers‘. In this paper we apply the same technique to decentralized control, when specifications are imposed on ’local‘ models of the ’global‘ process; in this way we remove the restriction in some earlier work that the plant and specification (marked) languages be prefix-closed. We then solve a more general problem of ’coordination‘: namely how to determine a high level ’coordinator‘ that forestalls conflict in a decentralized architecture when it potentially arises, but is otherwise minimally ’intrusive‘ on low-level control action. Coordination thus combines both vertical and horizontal modularity. The example of a simple production process is provided as a practical illustration. We conclude with an appraisal of the computational effort involved.

W. Murray Wonham

Papers

Think Globally, Act Locally: Decentralized Supervisory Control

Supervisory Control of Discrete-Event Systems

Modular Control and Coordination of Discrete-Event Systems

The infimal prefix-closed and observable superlanguage of given language

Supervisory control of communicating processes