Papers by Siri-on Setamanit
The importance of inventory management has been evident for a long time since inventories are not... more The importance of inventory management has been evident for a long time since inventories are not only necessary for operations, but they also contribute to customer satisfaction. However, holding inventory comes with costs such as inventory carrying cost and opportunity cost. Therefore, it is vital for a firm to find way to manage its inventory to maximize customer service, minimize total investment, and maintaining operation efficiency. Unfortunately, these three objectives are frequently in conflict with each other. In this paper, the author presents a simulation-based approach to evaluate the impact of continuous and periodic review policies on supply chain performance measures including cost and service level. This simulation model is served as an experimental platform for manager to evaluate diverse inventory policies for different products under different circumstances. For the case study company, continuous and periodic review policies provide relatively the same costs given the same service level.
The importance of inventory management has been evident for a long time since inventories are not... more The importance of inventory management has been evident for a long time since inventories are not only necessary for operations, but they also contribute to customer satisfaction. However, holding inventory comes with costs such as inventory carrying cost and opportunity cost. Therefore, it is vital for a firm to find way to manage its inventory to maximize customer service, minimize total investment, and maintaining operation efficiency. Unfortunately, these three objectives are frequently in conflict with each other. In this paper, the author presents a simulation-based approach to evaluate the impact of continuous and periodic review policies on supply chain performance measures including cost and service level. This simulation model is served as an experimental platform for manager to evaluate diverse inventory policies for different products under different circumstances. For the case study company, continuous and periodic review policies provide relatively the same costs given the same service level. Furthermore, this paper also applies Design of Experiment (DOE) to an inventory simulation model. DOE is used to investigate factors that affect performance including variation in demand, lead time, and review interval, and to analyze the interaction of these factors. All three factors affect total costs but in different magnitude. Interaction between lead time and review interval is also significant. The results of the experimentation enables managers to gain better understanding of different inventory policies and be able to select the configuration that best suit the company's objective.
ABSTRACT To survive in today competitive environment, companies need to improve customer service ... more ABSTRACT To survive in today competitive environment, companies need to improve customer service while reducing costs. One way to address this challenge is to effectively and efficiently managing inventory. Companies carry inventory to ensure the level of customer service and avoid lost sales. However, holding inventory comes with costs such as inventory carrying cost and opportunity cost. There are several inventory policies proposed in the literature which aim to manage the difficult trade-off between minimizing the costs of holding inventory and satisfying customer demand. Unfortunately, these policies tend to be generic and work well under assumptions. Some assumptions may be contradicted to real-world practice, for example, stable and deterministic customer demand. In addition, certain policy that works well in one industry may not be appropriate for other industry under different environment. As a result, there is a need to develop a simulation model to determine a suitable inventory policy and explore the effect of inventory policy on supply chain performance, including cost and service level (fill rate) for a particular company or supply chain. In this paper, a case study of a beverage distribution center was used to illustrate the use of simulation to identify the most suitable inventory policy. Simulation model and simulation optimization can serve as a guiding tool to develop appropriate inventory policy. Furthermore, experimenting with the simulation model can also help manager to understand the effect of change in environment/condition on the effectiveness of the inventory policy.
To manage supply chain efficiently and effectively, the members of the supply chain should collab... more To manage supply chain efficiently and effectively, the members of the supply chain should collaborate and cooperate. It is known that information sharing and visibility are important factors that contribute to supply chain coordination. The visibility in real customer demand can help reduce the bullwhip effect, improve customer service, and reduce costs. Vendor managed inventory (VMI) is an approach that allows suppliers/vendors to access to their customer's inventory and demand information. The benefits of VMI have been reported in many studies. However, the gain that each member of the supply chain realized could be different. Some studies show that upstream members benefit more than the downstream ones, while some studies show the opposite results. Therefore, some members of the supply chain are still reluctant to adopt the VMI practice since they are not sure whether the benefits gain will justify the costs incurred. In this paper, simulation model is used to explore the effect of VMI implementation on supply chain costs both on system-wide level and on member level. It was found that VMI helps reduce total supply chain costs. However, the level of cost reduction differs significantly among members depending on the types of the implementation. As a result, it is important to establish the level of investment required and benefit shared for each member before implementing VMI. The members that may experience less cost reduction should be offered higher benefit share (or required less investment). Otherwise, the whole supply chain may lose the opportunity to gain additional benefits from implementing VMI. In addition, the benefits gained from VMI also vary depending on supply chain environment. Simulation model can be used as a guiding tool for establishing appropriate investment and benefits sharing structure for VMI implementation in different supply chain conditions.
Global software development (GSD) has become a dominant paradigm in the software industry. Conduc... more Global software development (GSD) has become a dominant paradigm in the software industry. Conducting development projects in multiple countries offers many potential benefits including reduction in development cost and reduction in time-to-market especially trough the use of follow-the-sun strategy. However, GSD also poses challenges and difficulties due to geographic dispersion, time-zone differences as well as cultural and language differences. Thus, few GSD projects have been able to realize the full benefits of follow-the-sun development. This raises the question whether follow-the-sun strategy is the best way to pursue in order to reduce development time. What need to be done to ensure that the full benefits of follow-the-sun are achieved? In this paper, we described a hybrid simulation model of the software development process that is specifically architected to examine GSD projects. Then, we illustrated how project managers can use such model to support project planning and process improvement. We found that, in general, one should avoid using follow-the-sun strategy since it requires too much communication and coordination between sites, which resulted in higher effort and longer duration. If one is determined to use a follow-the-sun strategy, three development sites working in 24- hour cycle are needed in order to reduce cycle time.
Software Process: Improvement and Practice, 2007
We describe a hybrid computer simulation model of the software development process that is specif... more We describe a hybrid computer simulation model of the software development process that is specifically architected to study alternative ways to configure global software development (GSD) projects, including phase-based, module-based, and follow-the-sun allocation strategies. The model is a hybrid system dynamics and discrete-event model. In this paper, test cases have been developed for each allocation strategy, and project duration is computed for each configuration under a range of plausible assumptions for key parameters. The primary finding is that although under ideal assumptions follow-the-sun is able to produce impressive reductions in time-to-market, under more realistic assumptions the reverse is true, thus corroborating findings by other researchers. We also conducted a factorial design to examine the impact of GSD factors including distance, culture, language, trust, and time zone on project duration under different task allocation strategies. The analysis reveals that different factors affected the performance of the selected allocation strategies in unique ways. These findings show how the unique ability of our GSD model to represent detailed development processes and work artifact transfer allows researchers to address challenging questions that are critical to GSD project success.
We describe a hybrid computer simulation model of the software development process that is specif... more We describe a hybrid computer simulation model of the software development process that is specifically architected to study alternative ways to configure global software development projects, including phased-based, module-based, and follow-the-sun allocation strategies. The model is a hybrid system dynamics and discrete event model. In this paper, test cases have been developed for each allocation strategy, and project duration under each configuration is computed under a range of plausible assumptions for key parameters. The primary finding is that although under ideal assumptions, follow-the-sun is able to produce impressive reductions in time-to-market, under more realistic assumptions the reverse is true, thus corroborating findings by other researchers. Further analysis reveals the presence of some interaction between the assumptions, but the results remain robust.
Data mining results about fault detectors are typically assessed in terms of their predictive acc... more Data mining results about fault detectors are typically assessed in terms of their predictive accuracy (PDs). While interesting, such results may not convince a project manager that they should reallocate their scarce resources to implementing a new technology on their project. This article proposes a methodology for assessing the merits of defect detectors learnt from software repositories of static code measures (Halstead and McCabe). Using process simulation, we find situations where the use of such detectors is useful or useless. 1 e.g. A recent report on software defect detectors in IEEE Transactions on Software Engineering used just 2 data sets [1].
Software Process: Improvement and Practice, 2008
Adopting new tools and technologies on a development process can be a risky endeavor. Will the pr... more Adopting new tools and technologies on a development process can be a risky endeavor. Will the project accept the new technology? What will be the impact? Far too often the project is forced to adopt the new technology without planning how it will be applied on the project or evaluating the technology's potential impact. In this article, we provide a case study evaluating a new technology. Specifically we assess the merits of an automated requirements analysis tool. First, we provide a background on automated requirements analysis tool technology. Then, using Process Simulation (P-SIM), we find situations where the use of this new technology is useful and situations where the use of this new technology is useless for large-scale NASA projects that utilize a process similar to the IEEE 12207 systems development life cycle. The method can be applied in assessing the impact (including Return on Investment), breakeven point, and the overall value of applying any tool on a project. Copyright © 2008 John Wiley & Sons, Ltd.
Adopting new tools and technologies on a development process can be a risky endeavor. Will the pr... more Adopting new tools and technologies on a development process can be a risky endeavor. Will the project accept the new technology? What will be the impact? Far too often the project is asked to adopt the new technology without planning how it will be applied on the project or evaluating the technology’s potential impact. In this paper we provide a case study evaluating one new technology. Specifically we assess the merits of an automated defect detection tool. Using process simulation, we find situations where the use of this new technology is useful and situations where the use of this new technology is useless for large-scale NASA projects that utilize a process similar to the IEEE 12207 systems development lifecycle. The method can be applied to assessing the impact (including Return on Investment), break even point and the overall value of applying any tool on a project.
Distributed development is becoming a dominant paradigm in the software industry. Conducting deve... more Distributed development is becoming a dominant paradigm in the software industry. Conducting development projects in multiple countries offers many potential benefits including significantly reduced cost and better response times. When using a globally distributed software development paradigm, the process used to develop software is more important than ever. Software Process Simulation Modeling (SPSM) can be used to support companies in
Software engineering (SE) truisms capture broadlyapplicable principles of software construction. ... more Software engineering (SE) truisms capture broadlyapplicable principles of software construction. The trouble with truisms is that such general principles may not apply in specific cases. This paper tests the specificity of two SE truisms: (a) increasing software process level is a desirable goal; and (b) it is best to remove errors during the early parts of a software lifecycle.
A standard methodology in the process simulation community is to build simulations using high-end... more A standard methodology in the process simulation community is to build simulations using high-end visual programming (VP) system with powerful graphical front-ends. Many such VP tools exist including Vensim (see ), the Statemate state-based simulation model by i-Logix 1 , the Extend discrete event simulation tool 2 , just to name a few. Various benefits come from these VP tools including acceptance, debugging support and increased comprehension of the models.
Today, organizations like NASA and the US Department of Defense make heavy use of Independent Ver... more Today, organizations like NASA and the US Department of Defense make heavy use of Independent Verification and Validation (IV&V) techniques to improve the quality of systems and reduce the risks associated with the deployment of those systems. As more firms move to global outsourcing of their software development projects, IV&V will become increasingly valuable to companies as part of the their project activities. As a result, there is a critical need for cost effective IV&V.
International Journal of Software Engineering and Knowledge Engineering, 2003
In this paper, we present a \forward-looking" decision support framework that integr... more In this paper, we present a \forward-looking" decision support framework that integrates timely metrics data with a simulation based defect model of the software development process in order to support software project management decisions regarding product quality. These predictions are evaluated using Outcome Based Control Limits (OBCLs) and Bi-Directional (both forward and reverse) simulation models of the software de- velopment process. The Bi-Directional models provide useful guidance to the program manager when evaluating possible corrective actions on a project that has gone outside the OBCLs. The forward model predicts the potential performance impacts of the pro- posed corrective actions. The reverse simulation models are new and take the desired system outcome as the starting point and represent the system as it evolves backward in time to identify the necessary starting point to achieve the desired outcome. The approach is presented using an illustrative example.
With the increased pressure to reduce cost, reduce development time, and improve quality, many so... more With the increased pressure to reduce cost, reduce development time, and improve quality, many software companies are moving toward using a Globally Distributed Software Development (GSD) paradigm. Due to the challenges and difficulties with GSD, researchers and practitioners are attempting to identify key success factors for GSD projects. Based on our previous work, we found that the key success factors can be different depending upon specific project characteristics. To ensure a successful outcome, project managers have to focus on the right success factors for their particular project. In this paper, we illustrate how a GSD simulation model can be used to represent a specific project and to identify key success factors for that project. We use a case study from an actual software development firm. We also perform sensitivity analysis to assess the magnitude of the performance impact for the key factors for the specific project. For the case study site, which uses a combination of phase-based and module-based task allocation strategies, we found that team member familiarity, frequency of team meetings, and communication frequency each have a strong impact on total project effort and duration.
Global software development poses a number of challenges and difficulties as well as significant ... more Global software development poses a number of challenges and difficulties as well as significant potential benefits. In order to be successful, companies need to adapt and improve their processes to support this kind of development. Strong project planning and management is also required. Software process simulation modeling has been used to address a variety of issues in software development projects ranging from strategic management, project planning and control, process improvement, to training and understanding. We believe that a hybrid simulation model combining system dynamics and discrete-event models is needed to effectively model global software development projects. In this paper, we describe such a model, and focus on the use of the model to support project planning and process improvement in global software development. Example questions/issues that can be addressed by our GSD model are provided, along with an illustrative application.
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Papers by Siri-on Setamanit