Browsing by Author "Welch, Donald J."
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Item Building Self-Reconfiguring Distributed Virtual Environments(1998-10-15) Welch, Donald J.A distributed virtual environment may be required to reconfigure itself to compensate for various conditions that can occur during execution. An example is the reentry of a virtual environment that was previously reconfigured out of the distributed virtual environment due to failure. If there is a human user of this virtual environment, care must be taken to insure that he is brought back into the distributed virtual environment in a way that makes sense. He cannot regain control of a tank that is out of ammunition while a computer-based simulation controls actively participating tanks. The compensating reconfiguration function of a distributed virtual environment must detect conditions that dictate reconfiguration. It must determine the proper course of action and act on it, bringing the distributed virtual environment to a stable state as quickly as possible. Proper reconfiguration of a distributed virtual environment requires that the compensating reconfiguration software know the system configuration, the virtual state, and the mapping between them. Building compensating reconfiguration software using traditional means is laborious and error prone. A rule-based tool that uses abstract views of the distributed virtual environment is a better way to produce compensating reconfiguration software. To show the viability of this approach I have developed a rule-based tool called Bullpen. This research compares Bullpen against manual coding in a case study that ranges over a wide array of requirements changes. The results of this case study show that using Bullpen to build compensating reconfiguration components is superior to manually building the software in the kind of environments most commonly found in the military DVE domain. Using Bullpen takes less effort and is less complex than using manual programming techniques. The resulting component is less error prone and has acceptable reaction time. (Also cross-referenced as UMIACS-TR-98-18)Item Domain-Driven Reconfiguration in Collaborative Virtual Environments(1998-10-15) Welch, Donald J.; Purtilo, James M.When virtual environments (VE) collaborate to create a shared virtual world, events occur that can have catastrophic effects on that virtual world. These events can be system events, such as the loss of a host or a network link to that host. They can also be events that happen only in the virtual world, for example, a virtual activity that migrates, bringing increased activity to a different VE. To maintain acceptable or realistic behavior can require the restructuring of the collaborative virtual environment (CVE) during execution. The restructuring must take place in accordance with a set of rules mandated by the domain and specific application. The reconfiguration must occur quickly, to maintain realism for the users. Automatic restructuring brings the added benefit of fewer support staff. We call the automatic restructuring of a distributed application with respect to these rules Domain-Driven Reconfiguration and we have developed a software engineering environment to support its inclusion in CVEs. (Also cross-referenced as UMIACS-TR-97-32)Item Interconnecting Distributed Legacy Systems: Virtual Environment Domain Example(1998-10-15) Welch, Donald J.; Purtilo, James M.As the power and utility of virtual reality environments increases, so do the potential benefits found from combinding several such environments. But doing so presents the developer with a host of difficult distributed systems issues. This paper explores what some of these issues are within the VE domain, relates our successes to date in overcoming these problems by means of various automated tools, and suggests ways to apply our results other target domains. (Also cross-referenced as UMIACS-TR-96-88)Item Software Engineering of Virtual Environments: Integration and Interconnection(1998-10-15) Welch, Donald J.; Purtilo, James M.Virtual Environments(VEs) are proving to be valuable resources in many fields, and they are even more useful when they involve multiple users in distributed environments. Many useful VEs were designed to be stand-alone applications, without consideration for integrating them into a distributed VE. Our approach to connecting VEs is to define an abstract model for the interconnection, use integration tools to do as much of the work automatically as possible, and use a run-time environment to support the interconnection. With our experiences to date, we are learning that certain classes of techniques are common to all solutions using this approach. We have summarized these in a set of requirements and are building a system that features these techniques as first class objects. In the future you will be able to solve these interconnection problems cheaply, plus engineers of future VEs will have some guidance on how they should organize their implementations so that interconnection with other VEs will be easier. In this paper we coin the phrase "software engineering of virtual environments" (SEVE) to describe the above activities. (Also cross-referenced as UMIACS-TR-96-89)Item Zubin: A Software Engineering Environment for Interconnecting Legacy Virtual Environments(1998-10-15) Welch, Donald J.; Purtilo, James M.As the power and utility of virtual reality environments increases, so do the potential benefits found from combining several such environments. But doing so presents the developer with a host of difficult software engineering issues. This paper explores what some of these issues are within the VE domain, relates our successes to date in overcoming these problems by means of various automated tools, and suggests ways to apply our results other target domains. (Also cross-referenced as UMIACS-TR-96-87)