Modelling techniques used for network systems

Network systems are used in the design and analysis of a great number of problems and this paper describes how the MOSS (MOdelling SyStems) system is used to store, update and interrogate networks in the form of models.The paper was presented at a one-day symposium on Networks, organized by the Computer-Aided Design Specialist group of the British Computer Society and held on the 18th March 1974.     

Information systems outsourcing: A literature analysis

Outsourcing has become one of the strategies adopted by businesses to manage their IS. During the last few years, the use of outsourcing has resulted in an increase in the volume of literature devoted to it. We decided therefore to analyse the literature with the aim of identifying the main topics, the methodologies most often applied and the authors and countries that have contributed most to the area of IS outsourcing. We also intended to offer suggestions on improving research in this field. The paper thus provides a review of articles about IS outsourcing published in the most prestigious journals of the IS area and journals of Management or Business.     

Modelling flexible manufacturing systems using mean-value analysis

Flexible manufacturing systems (FMS) represent an important new development in automated manufacturing of parts with mid-volume demand. In the design and operation of these complex systems, it is useful to have tools that predict their performance under various conditions. This paper describes one such tool called MVAQ, a computer program based on mean-value analysis of queues. Part production rates, machine utilization and average work-in-process sizes are all easily obtained using MVAQ. The reader is advised on when MVAQ should be used for modelling FMSs and how the program can be used. A simple design example is given to illustrate the use of MVAQ. A brief tutorial on the theory behind MVAQ is also included.     

A structurational analysis of how course management systems are used in practice

An understanding of the role of e-learning needs to be accompanied by a realisation of the variety of social dimensions in the innovation process. As most studies in this domain are typically context-independent, this research, building on structuration theory, seeks to investigate different interpretations and uses of course management systems (CMSs) in an academic context. For the purpose of this research, a case study has been conducted on the introduction of a CMS in a higher education institution. Findings from this empirical study have been drawn on to illuminate how this system is employed in disparate manners by different groups of academics and what are the reasons behind this discrepancy. The study also demonstrates that the practice lens (Orlikowski, W.J., 2000. Using technology and constituting structures: a practice lens for studying technology in organizations. Organization Science, 11 (4), 404–428), viewing the use of technology as a process of enactment, presents a useful insight for explanation and synthesis of the variations in usage patterns.     

Modelling and performance analysis of inter-processor messaging in distributed systems

This paper addresses some performance modelling issues arising from the inter-processor messaging requirements of distributed real-time processing systems. We consider two basic classes of message transfer protocols, namely clocked schemes where message transfer is initiated as a periodic timed task, and event-driven schemes where the transfer mechanism is triggered by the messaging requests themselves. The aim is to maximize system efficiency by passing messages in batches. It is shown how the classes of protocols may be modelled by a two-stage queueing systems, which is analysed using the theory of imbedded Markov chains and semi-Markov processes. The results are used to show how the important performance measures are derived, and how the protocol parameters should be chosen to optimize the overall message system performance. The methods are illustrated by numerical examples.     

Electronic communication systems effects on the success of construction projects in United Arab Emirates

This research investigates the use of modern electronic communication management systems, and how these systems affect the success of construction projects in the United Arab Emirates (UAE). The research starts with a literature survey, and a brief background on how the communication mechanism works; how using these systems influence relationships amongst the project stakeholders, and consequently the projects success. Two case studies are introduced, followed by an analysis of results and conclusions.The first case study, based on action research, employs interactive tools to collect the evidence, including interviews, surveys, document review, and feedback on progress. The study uses success criteria from construction projects in the UAE, previously identified by the authors. This case study has revealed an organisational transformation trend, from functional, towards matrix and project structures. These types of change are taking place after the implementation of project electronic communication management systems into the client organisation, and are enhancing chances of project success.The second case study takes into consideration the co-existence of the new modern project electronic communication systems with the other traditional communication media. It has been shown that such an arrangement works both for the strategic benefit of the projects, and the projects stakeholders.In the areas of improvements to schedule and project control, the current research results are in agreement with pertinent published literature and research findings. However, the benefits for quality control during the design and construction phases of the project, in addition to potential improvements in the health safety and environment (HSE), remain debatable.     

Modelling manufacturing systems: A birth-death approach

An approximation method for modelling a manufacturing system is introduced. The system is considered as a queueing network, where each queue is limited in size, and interarrival and processing times are exponentially distributed. The birth-death approach is considered and an approximation method to reduce the dimension of the model is developed. The results are the marginal probability distribution of the number of units in each queue; other performance indices, such as mean queue lengths, utilizations of the working stations, and throughput can be easily obtained. The general procedure is applied to model, for example, queues in tandem, a split node, and a more complex network of queues. Simulation and, when possible, comparison with the exact solution show an acceptable error level of the proposed method.     

Modelling and analysis of multi-stage systems of mistuned bladed disks

A stochastic reduced-order modelling technique for multi-stage mistuned bladed disks assemblies is proposed. In a perturbation framework, the base-line reduced-order model is built using multi-stage cyclic symmetry modelling approach. Uncertainties are introduced in the modal space at the component level and further propagated in the global modal space. This results in a compact model suitable for statistical analyses based on Monte-Carlo simulations.Applications highlight the numerically efficiency of the proposed approach which features good correlation and convergence both from deterministic and probabilistic points of view. Statistical investigations on the forced response amplification show effects of multi-stage coupling on mistuning sensitivity.     

A systems life cycle for office automation projects

As office automation activities become more complex and interrelated, the need for generalized, systematic planning and control procedures increases. For data processing projects, systems life cycles have proven to be a highly effective planning and control mechanisms. This paper presents an analogous life cycle for office automation projects. It incorporates those unique characteristics of the office environment that preclude use of existing data processing life cycles. The paper concludes with an illustrative application of the office automation life cycle.     

A novel dynamic progress forecasting approach for construction projects

In this paper, we propose a novel construction project progress forecasting approach which combines the grey dynamic prediction model and the residual modified model to forecast the current progress during the construction phase. Firstly, four typical S-curves simplified from various sigmoid curves are proposed and fitted to the grey dynamic prediction model. For higher prediction accuracy, three different residual modified models are taken to amend the initial prediction value which was derived from the above step. The mean absolute percentage error (MAPE) and standard deviation of the estimate of Y (SDY) are used to assess the accuracy of the composite results. The better residual modified prediction model is adopted to combine the grey dynamic prediction model to form the novel progress forecasting approach. Then, practical completed construction cases are provided for testing the prediction ability of the proposed progress forecasting approach. Results show that the forecasting approach proposed to forecast construction progress during construction phase is able to get better prediction accuracy almost within 10% whether typical S-curves or practical cases. The new approach relatively provides an accurate, simple and stable method for predicting construction progress in comparison with the previous traditional forecasting methods.     

A critical analysis of the X.400 model of message handling systems

The CCITT X.400 model of store and forward Message Handling Systems (MHS) serves as a common basis for the definition of electronic mail services and protocols both within CCITT and ISO. This paper presents an analysis of this model and its related recommendations from two perspectives. First the concepts of service, protocol and interface are discussed together with their application to this model; second the positioning within ISO's reference model for Open Systems Interconnection (OSI) is commented on.     

Modelling and analysis of strategies in the design of WSAN coordination systems

During the past five years, considerable research has been reported on the design of various coordination systems for Wireless Sensor and Actor Networks (WSANs). Though the coordination mechanism taxonomy was presented, there has been no work published for the performance comparison among these different strategies or protocols quantitatively. In this paper, we attempt to address this challenge. The contribution of this paper is as follows: (i) an approach for the performance comparison among different strategies of sensor-actor coordination in WSANs is proposed; (ii) analytical models to abstract the system characteristics and operation for each kind of solutions are developed; (iii) the performance of each individual strategy under various conditions is analysed; (vi) the performance among three typical strategies is compared. The results may be helpful for the users to understand the advantage of each strategy over others under a certain condition.     

Model-based construction and verification of critical systems using composition and partial refinement

This article introduces a new model-based method for incrementally constructing critical systems and illustrates its application to the development of fault-tolerant systems. The method relies on a special form of composition to combine software components and a set of proof rules to obtain high confidence of the correctness of the composed system. As in conventional component-based software development, two (or more) components are combined, but in contrast to many component-based approaches used in practice, which combine components consisting of code, our method combines components represented as state machine models. In the first phase of the method, a model is developed of the normal system behavior, and system properties are shown to hold in the model. In the second phase, a model of the required fault-handling behavior is developed and “or-composed” with the original system model to create a fault-tolerant extension which is, by construction, “fully faithful” (every execution possible in the normal system is possible in the fault-tolerant system). To model the fault-handling behavior, the set of states of the normal system model is extended through new state variables and new ranges for some existing state variables, and new fault-handling transitions are defined. Once constructed, the fault-tolerant extension is shown, using a set of property inheritance and compositional proof rules, to satisfy both the overall system properties, typically weakened, and selected fault-tolerance properties. These rules can often be used to verify the properties automatically. To provide a formal foundation for the method, formal notions of or-composition, partial refinement, fault-tolerant extension, and full faithfulness are introduced. To demonstrate and validate the method, we describe its application to a real-world, fault-tolerant avionics system.     

Mobile Learning projects – a critical analysis of the state of the art

This paper provides a critical analysis of Mobile Learning projects published before the end of 2007. The review uses a Mobile Learning framework to evaluate and categorize 102 Mobile Learning projects, and to briefly introduce exemplary projects for each category. All projects were analysed with the criteria: context, tools, control, communication, subject and objective. Although a significant number of projects have ventured to incorporate the physical context into the learning experience, few projects include a socializing context. Tool support ranges from pure content delivery to content construction by the learners. Although few projects explicitly discuss the Mobile Learning control issues, one can find all approaches from pure teacher control to learner control. Despite the fact that mobile phones initially started as a communication device, communication and collaboration play a surprisingly small role in Mobile Learning projects. Most Mobile Learning projects support novices, although one might argue that the largest potential is supporting advanced learners. All results show the design space and reveal gaps in Mobile Learning research.     

A quantitative method used in negotiation support systems

It is important for small and medium sized business to enter international market with an electronic international trade network-the Marketplace, which is a large and synthetic computer-based network to enable an organization to engage in buying and selling products and services across national borders almost as easily as one can conduct such business locally. As one of its necessary components, Negotiation Support Systems(NSS) aid negotiators to bargain and reach agreement in negotiation process. On the basis of discussing the framework and capabilities of the Marketplace and the theory of negotiation, this paper introduces a quantitative method used in negotiation support system, which systematically analyses trade-offs between variables and is an additive scoring method to get to the efficient frontier in order to recommend high quality alternatives near it. The principle and techniques of this approach are also suggested.     

A layout technique for class diagrams to be used in product configuration projects

The use of product configurators has produced a range of benefits for several companies, such as minimizing the use of resources and shortening the lead times in product specification processes. When developing a product configurator, two kinds of models are often created, namely analysis models and design models. Since the task of describing product knowledge in analysis models involves domain experts, the analysis language has to be easily understandable in order to avoid the need for extensive training. For this task, the so-called Product Variant Master (PVM) diagramming technique is often applied. With regard to the design model, the requirements for the language focus more on a formalized and rich language, which is why class diagrams are often applied. To avoid the use of different modelling languages in the analysis and design phase, this paper proposes the layout technique ‘Vertically Aligned Class Diagrams’ (VACDs), which incorporate the usability of PVMs into class diagrams. To validate the usefulness of the VACD technique, the paper compares VACDs to PVMs and class diagrams in a utility analysis and a usability experiment. These investigations strongly indicate that VACDs maintain to a great extent the combined advantages of PVMs and normally drawn class diagrams. Thus, the use of VACDs in configurator projects has the potential to increase efficiency, improve communication and reduce errors.     

Method and system for Multi-Attribute Market Value Assessment in analysis of construction and retrofit projects

Multi-Attribute Decision-Making (MADM) methods prioritize the alternatives of comparative projects quite accurately. Problems arise when there is a need to determine the utility degrees and market values of the project alternatives. This becomes especially important for establishing the market value of real estate property in tender offers. However, the available MADM methods cannot accomplish this. Thus the authors of this article developed the MAMVA method, which permits determining the utility degrees and market values of project alternatives, and also developed a system on the basis of this developed method. This article presents the proposed Multi-Attribute Market Value Assessment (MAMVA) Method and the Decision Support System for Construction and Retrofit Projects (DSS-CRP). It also presents a case study to demonstrate the effectiveness of this method and system. The application of the MAMVA Method and DSS-CRP System for prioritizing and for determining the utility degrees and market values of construction and retrofit projects under consideration for financing by the European Economic Area (EEA) and Norway Financial Mechanism Grant made it possible to decrease the amount of requested support.This article also presents the analysis and comprehensive assessment of the noted construction and retrofit projects. These were performed in consideration of the entire life cycle of a project and of needs satisfaction relevant to all the groups interested in a project. The developed MAMVA Method and DSS-CRP System permit assessing the appropriateness of projects under analysis in conceptual and qualitative forms. This method and system automatically submit the values of the project alternatives.     

Power: A critical systems development factor

Information system development methodologies for complex management support systems require the information analyst to utilize concepts and techniques which are frequently viewed as being too intangible and abstract. The analyst's knowledge and techniques must accommodate the increased variations and complexities which commonly exist for management support systems at all levels of management.In this article, power is examined as an information systems development concept and as a basis for a technique which will enable the information analyst to identify the information requirements for management support systems more effectively.     

Database e-portfolio systems: A critical appraisal

This article surveys trends in the e-portfolio boom, relating the development of database portfolio systems to portfolio pedagogy. As the market for enterprise-level database systems has grown, portfolio has spread to become a term used to describe systems from assessment initiatives to institutional portals to academic records management tools. After examining materials and demonstration sites, I found that despite sometimes hyperbolic marketing, database portfolio systems have a troubling and mixed relationship to portfolio pedagogy.The article first discusses central concepts—not of portfolios per se, but of portfolio pedagogy. The article then surveys the development of the boom in enterprise database systems and chronicles prominent trends in those systems. Finally, the article makes critical recommendations for realigning database portfolio systems with portfolio pedagogy, and calls for greater involvement of computers and writing scholars in the development of database portfolios.