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This article examines the benefits and potential dangers of setting up computer simulations to make management decisions. The authors provide a framework integrating the technical procedures with the management of a simulation project. Simulation is a means of approximating real life conditions for the purpose of generating a history, manipulating the model, and predicting the outcome in a real life situation. While no model can be completely accurate, this is as good as any provided the correct information is used. The benefit is being able to alter any facet of the information and examine how changes would impact the plan without it costing additional money. The authors examine the cost of computer simulation and offer advice on how to create one with the Monte Carlo method.

The article offers information on the effectiveness of project management simulations in developing the competencies in experiential and experimental learning environments.

Purpose Improving healthcare quality has become a worldwide effort. Strategic problem solving (SPS) is one approach to improve quality in healthcare settings. This case study aims to illustrate the process of applying the SPS approach in implementing a quality improvement project in a referral hospital.Design/methodology/approach A project team was formed to reduce the hospital-acquired infection (HAI) rate in the neonatology unit. A new injection policy was implemented according to the root cause identified.Findings The HAI rate decreased from 6.4 per cent pre-intervention to 4.2 per cent post-intervention. The compliance of performing the aseptic injection technique significantly improved by 60 per cent.Practical implications This case study illustrated the detailed application of the SPS approach in establishing a quality improvement project to address HAI and injection technique compliance, cost-effectively. Other departments or hospitals can apply the same approach to improve quality of care.Originality/value This study helps inform other hospitals in similar settings, the steps to create a quality improvement project using the SPS approach. [ABSTRACT FROM AUTHOR]

In this paper, we show the process inspired by model checking which integrate temporal logic to the application of semi-structured data query. We investigate the potential ofatechnique based on CTL (Computation Tree Logic) model checking for evaluating queries expressed in (a subset of) XPath. Our research consists of query algebra, constraint understanding and expression mapping. The core of research is mapping the XMLquery algebra to an expression collection of temporal logic. We tryanew kind of query execution strategy to enhance the accuracy of semantic description of the XMLquery. For the purpose of supporting the generation of the formal specifications and reducing the mapping processing, the XMLquery constraint can be converted toaspecification of SPS (Specification Pattern System) through which we get the formula set to evaluate path queries directly on CTLformula. [ABSTRACT FROM AUTHOR]

With the rapid improvement of hardware, the constant evaluation of simulation development methodologies and environments has brought us a new challenge: simulations modernization. This paper presents a simulation knowledge discovery metamodel that extends the Object Management Group’s knowledge discovery metamodel by adding a simulation model package for enabling architecture-driven simulation modernization. While there are some endeavors that propose integration methods, modernization of legacy simulations has not been investigated. Architecture-driven modernization has been introduced as a process of comprehending and transforming existing software assets. It advocates a model-based approach to software modernization in which the knowledge extracted from software assets is captured in models that conform to a metamodel, namely the knowledge discovery metamodel. It specifies an ontology of software assets. Model transformations are then recommended as means of modernization of legacy assets. But diversity in methodologies and approaches to specify simulation modeling assets prohibits the Knowledge Discovery Metamodel from providing adequate meta definitions to capture knowledge in simulations. System Entity Structure has long been used for knowledge representation by the simulation community. It provides formalism for composition, taxonomy and coupling relations. Hence, System Entity Structure is proposed as an intermediate metamodel to capture the meta-constructs and their relations. It is then made available to define particular metamodels for particular simulation modeling methodologies or approaches. The promoted methodology is exercised with samples in order to collect evidence of its applicability. Metamodel segments are presented for knowledge discovery for discrete event systems specification and Modelica simulation programming language. A complete metamodel is then introduced for the real-time distributed simulation domain model of the German Aerospace Center (DLR) Institute of Flight Systems. Finally, this metamodel is used to introduce discovery artifacts. These samples provide valuable indications that the methodology works. [ABSTRACT FROM AUTHOR]

At SAC 2004, Junod and Vaudenay designed the FOX family based on the Lai-Massey scheme. They noted that it was impossible to find any useful differential characteristic or linear trail after 8 rounds of FOX64 or FOX128. In this paper, we provide the lower bound of differentially active S-boxes in consecutive rounds of the Lai-Massey scheme that has SPS as its F-function, and we propose the necessary conditions for the reachability of the lower bound. We demonstrate that similar results can be obtained with respect to the lower bound of linearly active S-boxes by proving the duality in the Lai-Massey scheme. Finally, we apply these results to FOX64 and FOX128 and prove that it is impossible to find any useful differential characteristics or linear trail after 6 rounds of FOX64. We provide a more precise security bound for FOX128. [ABSTRACT FROM AUTHOR]

Abstract: In parameter estimation, it is often desirable to supplement the estimates with an assessment of their quality. A new family of methods proposed by Campi et al. for this purpose is particularly attractive, as it makes it possible to obtain exact, non-asymptotic confidence regions under mild assumptions on the noise distribution. A bottleneck of this approach, however, is the numerical characterization of these confidence regions. So far, it has been carried out by gridding, which provides no guarantee as to its results and is only applicable to low dimensional spaces. This paper shows how interval analysis can contribute to removing this bottleneck. [Copyright &y& Elsevier]

Abstract: Model for simulation of the UA9 crystal-assisted collimation experiment at the CERN-SPS and simulation results are presented. The impact parameters and angles of halo particles for the first hits with the crystal primary collimator realized in the collimation experiment are considered. The impact parameters are comparable with the width of a non-efficient crystal cross-section due to the miscut angle between the crystal planes and surface. This fact explains both a considerable increase of the beam losses expected in the crystal with a positive miscut angle and as consequence the improved agreement of the simulation results with the UA9 experimental data. The dependence of the extraction efficiency of halo particles from the circulating beam on the crystal length increases in the case of the crystal miscut. Possibility to minimize the collimation leakage selecting the optimal offset of the secondary collimator-absorber relative to the crystal is discussed. It was shown that the crystal with a negative miscut angle gives a considerably larger number of particles hitting the absorber edge; therefore it is worse for the beam collimation. [Copyright &y& Elsevier]

Copyright of Journal of Central European Agriculture is the property of Journal of Central European Agriculture and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To allow an automatic formal analysis of requirements, the requirements have to be formalized first. However, logical formalisms are seldom accessible to stakeholders in the automotive context. Konrad and Cheng proposed a specification pattern system (SPS) represented in a restricted English grammar that can be automatically translated to logics, but looks like natural language. In this paper, we investigate whether this SPS can be applied to automotive requirements of BOSCH, in the sense that it is expressive enough to specify automotive behavioral requirements of BOSCH. We did a case study over 289 informal behavioral requirements taken from automotive BOSCH projects. We evaluated whether these requirements could be formulated in the SPS and whether the SPS has to be adapted to the automotive context. The case study strongly indicates that the SPS, extended with 3 further patterns, is suited to specify automotive behavioral requirements at BOSCH. [ABSTRACT FROM AUTHOR]

In this paper , an unusual and efficient usage of functional programming language Common LISP as simulation program (CLASP) for electronic circuits is proposed. The principle of automatic self-modifying program has enabled complete freedom in definition of methods for optimized solution of any problem and speeding up the entire process of simulation. A new approach to program structure in electronic circuit simulator CLASP is described. The definition of simple electronic devices as resistor, voltage source and diode is given all together with description of their memory management in program CLASP. Other circuit elements can be easily defined in the same way. Simulation methods for electronic circuits as linear and nonlinear direct current analysis (DC) are suggested. A comparison of performances of two different linear solvers (an original and the standard GNU GSL) for circuit equations is demonstrated by an algorithm for automatic generation of huge circuits. [ABSTRACT FROM AUTHOR]

Copyright of Ciencia en su PC is the property of Instituto de Informacion Cientifica y Tecnologica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Estimation of uncertainty propagation in watershed models is challenging but useful to total maximum daily load (TMDL) calculations. This paper presents an effective approach, involving the combined application of Rosenblueth method and sensitivity analysis, to the determination of uncertainty propagation through the parameters and structure of the HSPF (Hydrologic Simulation Program-FORTRAN) model. The sensitivity analysis indicates that the temperature is a major forcing function in the DO-BOD balance and controls the overall dissolved oxygen concentration. The mean and standard deviation from the descriptive statistics of dissolved oxygen data obtained using the HSPF model are compared to those estimated using Rosenblueth's method. The difference is defined as the error propagated from water temperature through dissolved oxygen. The error propagation, while considering the second order sensitivity coefficient in Rosenblueth's method, is observed to have a mean of 0.281 mg/l and a standard deviation of 0.099 mg/l. A relative low error propagation value is attributed to low skewness of dependent and independent variables. The results provide new insights into the uncertainty propagation in the HSPF model commonly used for TMDL development. [ABSTRACT FROM AUTHOR]

The existing routing protocol for sensor networking can be divided into proactive routing protocol, reactive routing protocol and hybrid routing protocol. Each routing protocol has its merits and shortcomings. The lifetime will end when the working routing protocol can no longer support the whole wireless sensor network. An adaptive method based on redundancy node and dual routing protocol was proposed in the study. Redundancy node, when wireless sensor network is being deployed, can divide the wireless sensor network into operating and sleeping modes, and can use the different routing protocol. Dual routing protocol individually designs two kinds of different routing protocols in the sensor node, using the merits of these two different kinds of routing protocols to accomplish the mission of sending the data. The scenario set up is when the wireless sensor network has been used for a long time; the power kept in these sensor nodes is different. It is possible that some sensor nodes contain lower power because the heavy load of work, and some with more power because of less work load. After we send a query to the source node and unfortunately find out there is more than one wireless sensor in the routing path, and if there is power shortage, we can only query a message to send the sink to the source node. At the meantime, the source node will judge the storing condition of the power in all the sensor nodes when sending the query from the sink to the source node. Then the target wireless sensor will send a broadcast to all the neighbors. If there is a sleeping node in the neighbor and run a second kind of routing protocol, the sleeping wireless sensor will wake up. The woken sensor node will build up a path to ensure the data get sent from the source to the sink. Simulation results showed that the proposed mechanism is about 44% of packet delivery ratio can be increased compared to existing proactive/reactive routing protocol. [ABSTRACT FROM AUTHOR]

In this paper we present a comparative study of two simulation programs, programs we have elaborated for the study of cache performance in the design phase. The first program is called Cache and is a trace-driven simulator and the second one is a simulator named, CDLR SPEC 2000. Cache is a simulation program for the analysis of cache memory systems. CDLR SPEC 2000 is a simulator based on traces for systems with cache memories. Despite the hit rate and miss rate parameters, reliability issues are also considered. [ABSTRACT FROM AUTHOR]

This paper presents a hybrid finite-difference time-domain-simulation program with integrated circuit emphasis (FDTD-SPICE) method for lossless transmission lines excited by a nonuniform electromagnetic field. An FDTD code is used to compute the excitation fields of the lines. Additional voltage sources, which denote the effect of the excitation fields, are computed with the results obtained by the FDTD method and incorporated into a SPICE model. The hybrid method can be used for nonlinear or time-varying loads, because the SPICE model allows easy incorporation of nonlinear or time-varying loads. Three cases, two transmission lines and a network, all inside a cavity excited by an incident electromagnetic field, are computed by using the presented method. The numerical results are compared with those obtained by using a 3-D FDTD code, and the agreement is generally good. The time needed by the hybrid method is much less than that needed by the FDTD code, because the lines can be ignored when the excitation fields of the lines are computed in the hybrid method. [ABSTRACT FROM AUTHOR]

The use of electronic language portfolios has been preferable to the use of common paper portfolios for ease of application - there is no need for accumulating a number of files of written papers, which solves the problem of storing space and, to some extent, helps reduce students' and teachers' workload. The study investigated learners' perceptions of employing electronic language portfolios for conducting various assignments in English for Specific Purposes. The research involved university students of different specializations. Learners' experience of employing portfolios and opinions on their benefits for improving language skills have been analyzed and statistically treated using SPSS software. The results show that students are positive about application of electronic portfolios in ESP classes. The use of online portfolios for various assignments helps teachers foster students' learning, encourages critical thinking, develops creativity, motivates learners to use digital technology, encourages collaboration of learners, and in the long run, leads to lifelong learning. [ABSTRACT FROM AUTHOR]

The control of a biped humanoid is a challenging task due to the hard-to-stabilize dynamics. Walking reference trajectory generation is a key problem. Linear Inverted Pendulum Model (LIPM) and Zero Moment Point (ZMP) Criterion-based approaches in stable walking reference generation are reported. In these methods, generally, the ZMP reference during a stepping motion is kept fixed in the middle of the supporting foot sole. This kind of reference generation lacks naturalness, in that the ZMP in the human walk does not stay fixed, but it moves forward under the supporting foot. This paper proposes a reference generation algorithm based on the LIPM and moving support foot ZMP references. The application of Fourier series approximation simplifies the solution, and it generates a smooth ZMP reference. A simple inverse kinematics-based joint space controller is used for the tests of the developed reference trajectory through full-dynamics 3-D simulation. A 12-DOF biped robot model is used in the simulations. Simulation studies suggest that the moving ZMP references are more energy efficient than the ones with fixed ZMP under the supporting foot. The results are promising for implementations. [ABSTRACT FROM AUTHOR]

PASTA WARS is a four-party negotiation/conflict simulation, in which participants must decide recurrently whether to adopt a cooperative stance or a competitive strategy toward one another. Participants are formed into four groups, each of which manages a flour mill that is attempting to sell its produce to a single purchaser, the local pasta restaurant, over a series of rounds. Each mill's profitability is dependent not only on its own manufacturing strategy but also on that of the three other mills. In this way, they are subtly placed in an iterated four-way Prisoner's Dilemma, and they must maneuver, in an environment of limited communication, to develop relationships with each other and to build trust as a means of enabling personal and joint gain. [ABSTRACT FROM AUTHOR]

The queue process at controlled junctions plays a fundamental role in many transportation problems, and they are a main determinant of the variability of traffic. Despite the large number of queue models developed in the last 50 years, there is a need for insight into the dynamic and stochastic behavior of traffic at controlled junctions. The existing models are often developed under heuristic, simplifying assumptions, which limit their application validity and interpretation opportunities. This article aims to fill this gap by formulating the queue process as probabilistic. This is done both at fixed and at vehicle actuated controls. Assuming a certain distribution of arrivals and departures one can calculate the probability distribution of queues at fixed control signals. Even if these distributions are assumed stationary, the probability of observing a number of vehicles in queue has a dynamic character. Vehicle actuated controls are in principle designed to adapt the duration of green times according to this dynamic process. By doing that, signal times become dynamic stochastic variables, thus vehicle delays and queues are still random processes in these systems. In this article we compare the performance of these two control types in view of network reliability. The models developed in this research are simple and require small computation times, and they are shown to be consistent with the more elaborate models used in microscopic simulation programs. [ABSTRACT FROM AUTHOR]

We develop beamforming algorithms for information relaying over shared slowly nonselective fading channels in wireless sensor networks. We assume that, prior to beamforming their received data to a destination, the relays preprocess them by either data amplifying or decoding. The beamforming weights are broadcasted by the destination to the relays and are formed based on the individual relay-destination channel coefficients and an m-bit description of the quality of each source-relay channel. For both relay data-preprocessing models, we present methods for optimizing the m-bit quantizer employed at each relay for encoding its source-relay channel quality level, and for choosing the beamforming weights at the destination, so as optimize the destination uncoded bit error rates. As our simulations and analysis reveal, a coarse single-bit description of each source-relay channel coefficient at the destination may suffice, as it results in only a small increase in uncoded bit error rates with respect to the case where full knowledge of the source-relay channel coefficients are exploited at the destination. [ABSTRACT FROM AUTHOR]

This paper introduces jNEP: a general, flexible, and rigorous implementation of NEPs (the basic model) and some interestenting variants; it is specifically designed to easily add the new results (filters, stopping conditions, evolutionary rules, and so on) of the research in the area. jNEP is written in Java; there are two different versions that implement the concurrency of NEPs by means of the Java classes Process and Threads respectively. There are also extended versions that run on clusters of computers under Java Party. JNEP reads the description of the currently simulated NEP from a XML configuration file. This paper shows how JNEP tackles the SAT problem with polynomial performance by simulating an ANSP. [ABSTRACT FROM AUTHOR]

Copyright of Computer Science (1407-7493) is the property of RTU Publishing House and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We extend Lemke's algorithm to solve a dynamic pricing problem. We identify an instance in which Lemke's algorithm fails to converge to an optimal solution (when an optimum does exist) and propose a constraint logic programming solution to this problem. We analyze the complexity of the extended Lemke's algorithm. Our analysis shows that, in the short term, dynamic pricing can be used to improve resource management efficiency. It is also shown that dynamic pricing can be used to manage the long-term behavior of demand. [ABSTRACT FROM AUTHOR]

To support student learning in biochemistry and related courses, a simulation program, the Protein Purification Program, offers an alternative multimedia-based tool. This program has now been translated to produce a Thai version. However, translation from the original into the Thai language is limited by the differences between the language characteristics of English and Thai. Therefore, use of the program with Thai students had a twofold purpose. It helped their understanding of the concepts of protein purification by allowing code switching between the languages, but it also improved their understanding of, and competence in scientific English, which is a vital skill for functioning as a modern biochemist. According to the results of the questionnaires, undergraduates using the Thai/English program scored significantly higher than those using only the English language program (p < 0.05). In addition, the interview data suggested that the Thai/English program had improved student understanding of the concepts of protein purification to a greater extent than a single language (English) program. Students' overall preference in terms of their learning using the Thai/English program was 4.15 on a 1-5 Likert scale. [ABSTRACT FROM AUTHOR]

A general configuration suitable for realizing low-pass and high-pass ladder filters and transformer simulator, depending on the passive element selection is proposed. The proposed network employs only grounded passive components without requiring matching conditions. The values of the synthetic inductances of the transformer and low-pass ladder filter can be changed independently. SPICE simulation results confirming the theoretical analysis are included. [ABSTRACT FROM AUTHOR]

The dependence of the active-layer structure on the performance of the deep-UV AlGaN light-emitting diodes (LEDs) was theoretically investigated with an APSYS simulation program. Several structure parameters such as well width, well number, barrier height, barrier width, and doping type were employed to study how these parameters change the band structures as well as the carrier distributions. The band offset and bowing parameter used in the theoretical analysis were extracted from the experimental results. Theoretical analysis shows that the nonuniform carrier distributions as well as the low hole concentrations, which caused by polarization-induced tilted band structures, play important roles in improving the performance of the AlGaN LEDs. Compensating this asymmetric band structure and increasing the hole density are the important keys to improve the AlGaN LED performance. Numerical simulation results suggest that the higher output power can be obtained when the active layer consists of only one quantum well with a width of 1–3 nm and two thicker n-doped barriers with a small Al composition. [ABSTRACT FROM AUTHOR]

Copyright of Teknoloji is the property of Engineering Science & Technology, an International Journal and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Based on a novel multidimensional deconvolution algorithm (MDA), this paper proposes a time-domain approach to synthesize the broadband SPICE-compatible macromodels of coupled interconnects. The multiple conductor interconnects are ex- cited either experimentally by TDR or numerically by the step-like source in finite difference time domain (FDTD) method. According to the time-domain scattered data, the macromodel of the inter- connect can be efficiently extracted by cascading several configuration-oriented coupled transmission lines (CCTL). Two examples are used to demonstrate the validity of the proposed approach. One is the equivalent models for differential pairs crossing an asymmetrical ground slot. The other is the crosstalk behavior prediction for a three-coupled microstrip line. The accuracy in broadband frequency range of the synthesized models of these two examples are checked both in time and frequency domain and compared with the direct-FDTD simulation. The agreement is favorably good. [ABSTRACT FROM AUTHOR]

This paper presents an accurate and systematic approach for analysis of the signal integrity of the high-speed inter- connects, which couples the full-wave finite difference time domain (FDTD) method with scattering (S) parameter based macromodeling by using rational function approximation and the circuit simulator. Firstly, the full-wave FDTD method is applied to characterize the interconnect subsystems, which is dedicated to extract the S parameters of the subnetwork consisting of interconnects with fairly complex geometry. Once the frequency-domain discrete data of the S parameters of the interconnect subnetwork is constructed, the rational function approximation is carried out to establish the macromodel of the interconnect subnetwork by employing the vector fitting method, which provides a more robust and accurate solution for the overall problem. Finally, the analysis of the signal integrity of the hybrid circuit can be fulfilled by using the S parameters based macromodel synthesis and simulation program with integrated circuits emphasis (SPICE) circuit simulator. Numerical experiments demonstrate that the proposed approach is accurate and efficient to address the hybrid electromagnetic (inter- connect part) and circuit problems, in which the electromagnetic field effects are fully considered and the strength of SPICE circuit simulator is also exploited. [ABSTRACT FROM AUTHOR]

Parallel traffic simulation is an application of parallel computing techniques that aims to decrease the computation time by engaging different processors of a multiprocessor system or different computers of a network. Very few traffic simulation models have this capability of parallel simulation. However, it is possible to upgrade a simulation program that is not capable of running parallel simulation by applying the method proposed in this article. The method involves dividing the network into regions and simulating each region under a separate instance of the program. Suitable interprocess communication techniques are employed to exchange data between different regions and synchronize time among the different regions. A significant increase in simulation speed is seen when the proposed method is applied to Paramics, a microscopic time-stepping simulation program. [ABSTRACT FROM AUTHOR]

In 1989 I was pleased and honored to be awarded the ORSA/TIMS (now INFORMS) John von Neumann Theory Prize for my work in portfolio theory, sparse matrices, and SIMSCRIPT. The following is a retrospective on my work in these fields. [ABSTRACT FROM AUTHOR]

Presents the result of a performance evaluation of a set of parallel conservative algorithms implemented in the Maisie parallel simulation language. Algorithms included in a set; Comparison of algorithm performance using the Ideal Simulation Protocol; Characteristics used to describe algorithm performance.

Reprints the article `A description of the SIMSCRIPT language,' which appeared in the 1964 issue of `IBM Systems Journal,' Volume 3, Number 1.

This paper uses computational complexity theory to assess the difficulty of various discrete event simulation problems. More specifically, accessibility of states, ordering of events, noninterchangeability of model implementations, and execution stalling for discrete event simulations are formally stated as search problems and proven to be NP-hard. The consequences of these results cover a wide range of modeling and analysis problems in simulation. For example, problems associated with certain variance reduction techniques, model verification, model validation, and the applicability of infinitesimal perturbation analysis, among others, are deemed intractable. [ABSTRACT FROM AUTHOR]

A new type of high-level robot command library is presented and demonstrated. Three robot programming languages have been analyzed and new robot command libraries created for three types of robot. The programming of three robots using the new high-level robot command library demonstrated that it was possible to program robots with different kinematic configurations without the programmer having any knowledge of the physical structure of the robots. The library commands contained simulations of the abilities of the robots as well as having the ability to control the physical robots. This paper shows how simulation can be incorporated into a high-level robot command library and how the command library can be used for the programming of three industrial robots. ©1999 John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

Presents a simulation of ferry traffic in the Aegean Islands, which is being used as a decision aiding system for regional development. Use of SIMSCRIPT II.5; Parameters; Inbuilt flexibility; Graphics interface; Queuing; Combination of scenarios and parameters; Importance to non-profit making itineraries that qualify for government subsidy.

Previous concepts of time flow mechanisms are inadequate for categorizing or describing the algorithms for time flow which may prove most efficient for a particular systems application. The work of Kiviat provides a more meaningful categorization. The patrolling repairman problem serves as an example of the ambiguity and inconsistency in the use of fixed time and next-event classification. Three algorithms for time flow in the patrolling model are offered. Theoretical development is provided for the two more sophisticated algorithms--the variable increment (VIA) and the minimum increment comparison (MICA). Comparison of execution times for the three algorithms shows the constant increment (CI) to be generally more efficient. The concept of a continuum of algorithms for representing the passage of time is advanced. Fixed time methods with δt considered a "clock tick" define one end of the continuum, and next-event methods utilizing strictly the push down/pop up stack approach define the other. Between these two extremes lie other algorithms possessing characteristics of both but which may prove more advantageous for any specific application of discrete system simulation. [ABSTRACT FROM AUTHOR]

The SIMSCRIPT programming system is especially designed to facilitate the writing of simulation programs. Digital simulations generally consist of a numerical description of "status", which is modified at various points in simulated time called "events". SIMSCRIPT simulations consist primarily of a collection of "event routines" written by the user describing how different kinds of events in a particular simulated world affect current status and cause future events. Status is described in terms of various "entities", "attributes", and "sets" as specified by the user. [ABSTRACT FROM AUTHOR]

This article focuses on simulation model representation. Simulation model development had remained a relatively unchanged technology for some 15 years. Revisions, extensions, and conveniences had been added to all the primary tools, the simulation programming languages (SPL's), but neither the conceptual advances nor the clerical conveniences attributed to the rapidly emerging software development technology were to be found. The SPL's created in the early 1960's served as representational tools for numerous projects and general purpose languages the chosen form of expression for even more numerous ones. However, stimulated by the ever-increasing demands for more complicated modeling efforts and pressed by advances in software development technology, alternative approaches to simulation model development were pushing into view. The simulation program produced by the program generator might require completion and some minor modification by a programmer familiar with the "target" SPL, but much of the drudgery associated with syntactic details would be removed.