On stopping a Markov decision process

In this report the same situation will be considered as in Hordijk, Dynamic programrrdng and Markov potential theory [3], viz. a countable state space Markov decision process which can be stopped. Costs have the so-called charge structure and the optimality criterion is the total expected gain. It will be shown, that an optimal strategy, consisting of a memoryless decision rule and a possibly nonmemoryless stopping rule, can be replaced by a strategy consisting of the same decision rule and a stopping rule which is an entry time

Modelling another transaction manager using parallel decision processes and a translation into an object-oriented program

Parallel behaviour can be modelled successfully by Paradigm, a modelling method using parallel decision processes. Its name is an acronym for PARalellism, its Analysis, Design and Implementation by a General Method. For a comprehensive discussion the reader is referred to Groenewegen [1986-1990]. In this paper Paradigm will be used to present a model for a transaction manager for a database management system. The purpose of the presented model is to split the tasks of a transaction manager into components in order to support the developping of a program that performs the tasks of these components including their interaction This model will be translated into an object-oriented program. Such a program is added not to give an efficient program for transaction management, but to show how the model can easily be translated into modules that form together the program. The program can serve as a basis for the implementation of a transaction manager on a system using several processors, using shared memory, although this might not be the most efficient implementation

System evolution by migration coordination

Collaborations between components can bemodeled in the coordination language Paradigm[3]. A collaboration solution is specified by loosely coupling component dynamics to a protocol via their roles. Not only regular, foreseen collaboration can be specified, originally unforeseen collaboration can be modeled too [4]. To explain how, we first look very briefly at Paradigm’s regular coordination specification. Component dynamics are expressed by state-transition diagrams (STDs), see Figure 1(a) for a mock-up STD MU in UML style. MU contributes to a collaboration via a role MU(R). Figure 1(b) specifies MU(R) through a different STD, whose states are so-called phases of MU: temporarily valid, dynamic constraints imposed on MU. The figure mentions four such phases, Clock, Anti, Inter and Small. Figure 1(c) couplesMU and MU(R). It specifies each phase as part of MU, additionally decorated with one or more polygons grouping some states of a phase. Polygons visualize so-called traps: a trap, once entered, cannot be left as long as the phase remains the valid constraint. A trap having been entered, serves as a guard for a phase change. Therefore, traps label transitions in a role STD, cf. Figure 1(b). Single steps from different roles, are synchronized into one protocol step. A protocol step can be coupled to one detailed step of a so-called manager component, driving the protocol. Meanwhile, local variables can be updated. It is through a consistency rule, Paradigm specifies a protocol step: (i) at the left-hand side of a ?? the one, driving manager step is given, if relevant; (ii) the right-hand side lists the role steps being synchronized; (iii) optionally, a change clause [2] can be given updating variables, e.g. one containing the current set of consistency rules. For example, a consistency rule without change clause, MU2:A!B ?? MU1(R):Clock triv ! Anti, MU3(R): Inter toSmall ! Small where a manager step ofMU2 is coupled to the swapping ofMU1 from circling clockwise to anti-clock-wise and swapping MU3 from intermediate inspection into circling on a smaller scale

Coordination in networked organizations : the Paradigm approach

Abstract An extension of the coordination specification language Paradigm is presented. In this set-up Paradigm models cater for multiple managers sharing the coordination of a set of common employees. A transition system semantics for the language is provided, that allows for reasoning about such constructions as delegation and self-management in matrix and general network organizations. An elaborated example illustrates the expressiveness of the proposed version of Paradigm. Key words: Paradigm, coordination, operational semantics, delegation, software architectur

Dynamic Consistency in Process Algebra: From Paradigm to ACP

The coordination modelling language Paradigm addresses collaboration between components in terms of dynamic constraints. Within a Paradigm model, component dynamics are consistently specified at vari

Architecting security with Paradigm

For large security systems a clear separation of concerns is achieved through architecting. Particularly the dynamic consistency between the architectural components should be addressed, in addition to individual component behaviour. In this paper, relevant dynamic consistency is specified through Paradigm, a coordination modeling language based on dynamic constraints. As it is argued, this fits well with security issues. A smaller example introduces the architectural approach towards implementing security policies. A larger casestudy illustrates the use of Paradigm in analyzing the FOO voting scheme. In addition, translating the Paradigm models into process algebra brings model checking within reach. Security properties of the examples discussed, are formally verified with the model checker mCRL2

Towards reduction of Paradigm coordination models

The coordination modelling language Paradigm addresses collaboration between components in terms of dynamic constraints. Within a Paradigm model, component dynamics are consistently specified at a detailed and a global level of abstraction. To enable automated verification of Paradigm models, a translation of Paradigm into process algebra has been defined in previous work. In this paper we investigate, guided by a client-server example, reduction of Paradigm models based on a notion of global inertness. Representation of Paradigm models as process algebraic specifications helps to establish a property-preserving equivalence relation between the original and the reduced Paradigm model. Experiments indicate that in this way larger Paradigm models can be analyzed

Embedded Markov processes and recurrence

No abstract

A formal model for total quality management

Total Quality Management (TQM) is a systematic approach to managing a company. TQM is systematic in the sense that it is uses facts through observation, analysis and measurable goals. There are theoretical descriptions of this management concept, but there is no formal model of it. A formal model can give a very precise description of the concept and will be useful in organisations that consider to use TQM. Furthermore it can give organisations that have adopted TQM already more insight into their own situation. We will use the formal modelling method Paradigm as this method can give a clear description of systems in which communication plays an important role. To be more precise, Paradigm is a modelling method for parallel behaviour that shows in detail the interaction among components. We present two models in this paper: one for reactive improvement, both with and without a role for a separate manager, and a model for proactive improvement. The models are not normative in the sense that companies should exactly use TQM as we describe it in order to do it successfully. At the other hand the models are also not theoretical in the sense that they give a precise description of the theory concerning TQM as this is known of books and articles. Moreover, by making the Paradigm models we had to add details to TQM that are not described in informal descriptions of books and articles. The application of Paradigm shows much more detail in the management of the improvement processes. It provides insight as to when a manager using TQM can and probably should make choices and decisions regarding the improvement process. Furthermore, the models show that precise communication between the parties involved is of crucial importance to apply TQM