University of Twente Publications
University of Twente Repository provides publications of UT scientific staff, in many cases full text and publicly available.
Type = Internal Report
Mostrando recursos 1 - 20 de 1.725
Improve OR-schedule to reduce number of required beds - Essen van, J. Theresia; Bosch, Joel M.; Hans, Erwin W.; Houdenhoven van, Mark; Hurink, Johann L.
After surgery most of the surgical patients have to be admitted in a ward in the hospital. Due to financial reasons and an decreasing number of available nurses in the Netherlands over the years, it is important to reduce the bed usage as much as possible. One possible way to achieve this is to create an operating room (OR) schedule that spreads the usage of beds nicely over time, and thereby minimizes the number of required beds. An OR-schedule is given by an assignment of OR-blocks to specific days in the planning horizon and has to fulfill several resource constraints....
Integral multidisciplinary rehabilitation treatment planning - Braaksma, A.; Kortbeek, Nikky; Post, Gerhard; Nollet, Frans
This paper presents a methodology to plan treatments for rehabilitation outpatients. These patients require a series of treatments by therapists from various disciplines. In current practice, when treatments are planned, a lack of coordination between the different disciplines, along with a failure to plan the entire treatment plan at once, often occurs. This situation jeopardizes both the quality of care and the logistical performance. The multidisciplinary nature of the rehabilitation process complicates planning and control. An integral treatment planning methodology, based on an integer linear programming (ILP) formulation, ensures continuity of the rehabilitation process while simultaneously controlling seven performance indicators...
Teaching Information Security Students to "Think thief" - Hartel, P.; Junger, M.
We report on an educational experiment where information security master students were encouraged to think out of the box. Instead of taking the usual point of view of the security engineer we challenged the students to take the point of view of the motivated offender. We report on the exciting ideas our students came up with, and on the lessons we learned in designing the course.
Generalization and specialization of object dynamics - Gamito Dignum, V.; Riet van de, R.P.; Wieringa, R.
This report presents a quite detailed analysis of the modeling approaches of different object-oriented database systems, namely ABSURD, OBLOG, MOKUM, TAXIS and GAL/LEO, with emphasis on the spuialization of object dynamics, in a taxonomic structure. It is done unifonnly l7y applying each system to the specification of an UoD example, the University world. The potentialities of the systems are compared and ambiguities discovered. An auempt to resolve some of these ambiguities is made. The issues dealing with inheritance and taxonomy of the dynamics of an UoD specification are particularly treated. The formaliza tion of specialization issues for events and processes,...
Process generalization in conceptual models - Wieringa, Roel
In conceptual modeling, the universe of discourse (UoD) is divided into classes which have a taxonomic structure. The classes are usually defined in terms of attributes (all objects in a class share attribute names) and possibly of events. For enmple, the class of employees is the set of objects to which attributes like name, emp# etc. are applicable, and to which events li.Jce change -salary, change -address etc. are applicable. The events belong to the class because they change attributes applicable to objects in the class. We can add one more level of specification and define, for each class, a...
Decentralized throughput scheduling - Jong de, Jasper; Uetz, Marc; Wombacher, Andreas
Motivated by the organization of online service systems, we study models for throughput scheduling in a decentralized setting. In throughput scheduling, we have a set of jobs j with values w(j), processing times p(j), and release dates r(j) and deadlines and d(j), to be processed non-preemptively on a set of unrelated machines. The goal is to maximize the total value of jobs scheduled within their time window [r(j),d(j)]. While several approximation algorithms with different performance guarantees exist for this and related models, we are interested in the situation where subsets of servers are governed by selfish players. We give a...
Nonparametric control charts for bivariate high-quality processes - Albers, Willem
For attribute data with (very) low rates of defectives, attractive control charts can be based on the maximum of subsequent groups of r failure times, for some suitable r≥1, like r=5. Such charts combine good performance with often highly needed robustness, as they allow a nonparametric adaptation already for Phase I samples of ordinary size. In the present paper we address the problem of extending this approach to the situation where two characteristics have to be monitored simultaneously. Generalization to the multivariate case is straightforward.
Effective coastal boundary conditions for dispersive tsunami propagation - Kristina, W.; Groesen van, E.; Bokhove, O.
We aim to improve the techniques to predict tsunami wave heights along the coast. The modeling of tsunamis with the shallow water equations has been very successful, but is somewhat simplistic because wave dispersion is neglected. To bypass this shortcoming, we use the (linearized) variational Boussinesq model derived by Klopman et al. [J. Fluid Mech. 657, 36--63, 2010]. Another shortcoming is that the complicated interactions between incoming and reflected waves near the shore are usually simplified by a fixed wall boundary condition at a certain shallow depth contour. To alleviate this shortcoming, we explore and present in one spatial dimension...
Efficient Modelling and Generation of Markov Automata (extended version) - Timmer, Mark; Katoen, Joost-Pieter; Pol van de, Jaco; Stoelinga, Mariëlle
This paper introduces a framework for the efficient modelling and generation of Markov automata. It consists of (1) the data-rich process-algebraic language MAPA, allowing concise modelling of systems with nondeterminism, probability and Markovian timing; (2) a restricted form of the language, the MLPPE, enabling easy state space generation and parallel composition; and (3) several syntactic reduction techniques on the MLPPE format, for generating equivalent but smaller models. Technically, the framework relies on an encoding of MAPA into the existing prCRL language for probabilistic automata. First, we identify a class of transformations on prCRL that can be lifted to the Markovian...
The Identification of Objects and Roles - object identifiers revisited - - Wieringa, Roel; Jonge de, Wiebren
In this paper we investigate the relation between object identifiers (oid’s), object classification and class change. We give a precise definition of a concept of oid that solves the problems with DB merges and with the representation of historical informati on. We also extensively treat the differences between these oid’s, keys, surrogates and pseudo-oid’s, which are the object identifiers often used in practice. We distinguish object classes from role classes by defining roles (instances of role classes) to be part of the state of objects (instances of object classes). An advantage of distinguishing classes from roles is that we can...
A method for building and evaluating formal specifications of object-oriented conceptual models of database systems - Wieringa, R.J.
This report describes a method called MCM (Method for Conceptual Modeling) for building and evaluating formal specifications of object-oriented models of database system behavior. An important aim of MCM is to bridge the gap between formal specification and informal understanding. Building a MCM model is a process that moves from the informal to the formal, evaluating the model is a process that moves back from the formal to the informal.
First, a general framework for information system development methods is given, that is used to indicate which elements are needed to build a particular information system development method. In general, the...
Toolkit for Conceptual Modeling (TCM): User's Guide and Reference - Dehne, F.; Wieringa, R.J.
The Toolkit for Conceptual Modeling (TCM) is a suite of graphical editors for a number of graphical notation systems that are used in software specification methods. The notations can be used to represent the conceptual structure of the software - hence the name of the suite.
This manual describes version 1.6 of TCM. TCM runs on Unbc systems with X Windows. The TCM ftp site is ftp://ftp.cs.vu.nl/pub/tcm. The TCM home page is http:/fwww.cs.vu.nl/~tcm. The use of TCM is free for education, academic research and other non-commercial purposes.
This version of TCM contains graphical editors for several kinds of documents, namely...
Axiomatic Specification of Database Domain Statics - Wieringa, Roel
In the past ten years, much work has been done to add more structure to database models 1 than what is represented by a mere collection of flat relations (Albano & Cardelli , Albano et al. , Borgida eta. , Brodie , Brodie & Ridjanovic , Brodie & Silva (1982], Codd (1979], Hammer & McLeod (1981], King (1984], King & McLeod , , Mylopoulos et al. , Smith & Smith 1977a & b). 2 The informal approach which most of these studies advocate has a number of disadvantages. First, a recent survey of some of the pro posed models by...
A conceptual model specification language (CMSL Version 2) - Wieringa, R.J.
Version 2 of a language (CMSL) to specify conceptual models is defined. CMSL consists of two parts, the value specification language VSL and the object spercification language OSL. There is a formal semantics and an inference system for CMSL but research on this still continues. A method for developing CMSL models is being developed. A start has been made with a workbench for CMSL. This report is intended to keep track of current results and open research problems.
Jackson System Development, Entity-relationship Analysis and Data Flow Models: a comparative study - Wieringa, R.J.
This report compares JSD with ER modeling and data flow modeling. It is shown that JSD can be combined with ER modeling and that the result is a richer method than either of the two. The resulting method can serve as a basis for a pratical object-oriented modeling method and has some resemblance to parts of well-known methods, like OMT. It is also argued that JSD and data flow modeling rest on opposite philosophies and cannot be combined in one modeling effort. This is illustrated by transforming a JSD model into a data flow model and listing the differences between...