Technical Reports from UMIACS

Permanent URI for this collectionhttp://hdl.handle.net/1903/7

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Start date: 1998End date: 1999

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Now showing 1 - 10 of 505
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    Probabilistic Object Bases
    (1999-11-23) Eiter, Thomas; Lu, James; Lukasiewicz, Thomas; Subrahmanian, V.S.
    There are many applications where an object oriented data model is a good way of representing and querying data. However, current object database systems are unable to handle the case of objects whose attributes are uncertain. In this paper, extending previous pioneering work by Kornatzky and Shimony, we develop an extension of the relational algebra to the case of object bases with uncertainty. We propose concepts of consistency for such object bases, together with an NP-completeness result, and classes of probabilistic object bases for which consistency is polynomially checkable. In addition, as certain operations involve conjunctions and disjunctions of events, and as the probability of conjunctive and disjunctive events depends both on the probabilities of the primitive events involved as well as on what is known (if anything) about the relationship between the events, we show how all our algebraic operations may be performed under arbitrary probabilistic conjunction and disjunction strategies. We also develop a host of equivalence results in our algebra, which may be used as rewrite rules for query optimization. Last but not least, we have developed a prototype probabilistic object base server using the VisiBroker ORB on top of ObjectStore. We describe experiments to assess the efficiency of different possible rewrite rules. (Also cross-referenced as UMIACS-TR-99-77)
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    Designing Storytelling Technologies to Encourage Collabortion Between Young Children
    (1999-12-08) Benford, Steve; Bederson, Benjamin B.; Akesson, Karl-Petter; Bayon, Victor; Druin, Allison; Hansson, Par; Hourcade, Juan Pablo; Ingram, Rob; Neale, Helen; O'Malley, Claire; Simsarian, Kristian T.; Stanton, Danae; Sundblad, Yngve; Taxen, Gustav
    We describe the iterative design of two collaborative storytelling technologies for young children, KidPad and the Klump. We focus on the idea of designing interfaces to subtly encourage collaboration so that children are invited to discover the added benefits of working together. This idea has been motivated by our experiences of using early versions of our technologies in schools in Sweden and the UK. We compare the approach of encouraging collaboration with other approaches to synchronizing shared interfaces. We describe how we have revised the technologies to encourage collaboration and to reflect design suggestions made by the children themselves. (Also cross-referenced as UMIACS-TR-99-76)
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    Single Display Groupware
    (1999-12-08) Bederson, Benjamin B.; Stewart, Jason; Druin, Allison
    We discuss a model for supporting collaborative work between people that are physically close to each other. We call this model Single Display Groupware (SDG). In this paper, we describe the model, comparing it to more traditional remote collaboration. We describe the requirements that SDG places on computer technology, and our understanding of the benefits and costs of SDG systems. Finally, we describe a prototype SDG system that we built and the results of a usability test we ran with 60 elementary school children. Through participant observation, video analysis, program instrumentation, and an informal survey, we discovered that the SDG approach to collaboration has strong potential. Children overwhelmingly prefer two mice to one mouse when collaborating with other children. We identified several collaborative styles including a dominant partner, independent simultaneous use, a mentor/mentee relationship, and active collaboration. (Also cross-referenced as UMIACS-TR-99-75)
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    Parameterized Modeling and Scheduling of Dataflow Graphs
    (1999-12-03) Bhattacharya, Bishnupriya; Bhattacharyya, Shuvra S.
    There is no abstract available. (Also cross-referenced as UMIACS-TR-99-73)
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    SHOE: A Knowledge Representation Language for Internet Applications
    (1999-10-28) Heflin, Jeff; Hendler, James; Luke, Sean
    It is our contention that the World Wide Web poses challenges to knowledge representation systems that fundamentally change the way we should design KR languages. In this paper, we describe the Simple HTML Ontology Extensions (SHOE), a KR language which allows web pages to be annotated with semantics. We present a formalism for the language and discuss the features which make it well suited for the Web. We describe the syntax and semantics of this language, and discuss the differences from traditional KR systems that make it more suited to modern web applications. We also describe some generic tools for using the language and demonstrate its capabilities by describing two prototype systems that use it. We also discuss some future tools currently being developed for the language. The language, tools, and details of the applications are all available on the World Wide Web at http://www.cs.umd.edu/projects/plus/SHOE. (Also cross-referenced as UMIACS-TR-99-71)
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    ViPEr-HiSS: A Case for Storage Design Tools
    (1999-10-27) Golubchik, Leana; Dunnick, Joseph; Hollingsworth, Jeffrey K.
    The viability of large-scale multimedia applications, depends on the performance of storage systems. Providing cost-effective access to vast amounts of video, image, audio, and text data, requires (a) proper configuration of storage hierarchies as well as (b) efficient resource management techniques at all levels of the storage hierarchy. The resulting complexities of the hardware/software co-design in turn contribute to difficulties in making accurate predictions about performance, scalability, and cost-effectiveness of a storage system. Moreover, poor decisions at design time can be costly and problematic to correct in later stages of development. Hence, measurement of systems after they have been developed is not a desirable approach to predicting their performance. What is needed is the ability to evaluate the system's design while there are still opportunities to make corrections to fundamental design flaws. In this paper we describe the framework of ViPEr-HiSS, a tool which facilitates design, development, and subsequent performance evaluation of designs of multimedia storage hierarchies by providing mechanisms for relatively easy experimentation with (a) system configurations as well as (b) application- and media-aware resource management techniques. (Also cross-referenced as UMIACS-TR-99-69)
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    PETS: A Personal Teller of Stories
    (1999-11-23) Montemayor, Jaime; Druin, Allison; Hendler, Jim
    Let us start by reading a story written by a seven year old child, entitled Michelle. "There once was a robot named Michelle. She was new in the neighborhood. She was HAPPY when she first came, thinking she would make friends. But it was the opposite. Other robots threw rocks and sticks. She was SAD. Now no one liked her. One day she was walking down a street, a huge busy one, when another robot named Rob came up and ask [sic] if she wanted to have a friend. She was SCARED at first but then realized that she was HAPPY. The other robots were ANGRY but knew that they had learned their lesson. Michelle and Rob lived HAPPILY ever after. No one noticed the dents from rocks that stayed on Michelle." (Druin, Research notes, August 1998) This is just one of many stories that children have written with the help of PETS (Druin et al. 1999a). The author of Michelle did not just write this moving story; she is also an integral member of the team that built our robots. As you read on, PETS will be further described. Our motivations behind building such an interactive robotic pet will also be discussed. In addition, the process of how we made this robotic technology with our team of adults and six children will be introduced. And with this, we will present cooperative inquiry (Druin 1999a), the methodology that we embrace as we discover insights about technology, education, science, engineering, and art. Finally, this chapter will close with reflections on what was learned from on-going research effort. (Also cross-referenced as UMIACS-TR-99-67)
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    Efficient Preconditioning of the Linearized Navier-Stokes Equations}
    (1999-10-16) Silvester, David; Elman, Howard; Kay, David; Wathen, Andrew
    We outline a new class of robust and efficient methods for solving subproblems that arise in the linearization and operator splitting of Navier-Stokes equations. We describe a very general strategy for preconditioning that has two basic building blocks; a multigrid V-cycle for the scalar convection-diffusion operator, and a multigrid V-cycle for a pressure Poisson operator. We present numerical experiments illustrating that a simple implementation of our approach leads to an effective and robust solver strategy in that the convergence rate is independent of the grid and the time-step, and only deteriorates very slowly as the Reynolds number is increased. (Also cross-referenced as UMIACS-TR-99-66)
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    Active Logics: A Unified Formal Approach to Episodic Reasoning
    (1999-10-14) Elgot-Drapkin, Jennifer; Kraus, Sarit; Miller, Michael; Nirkhe, Madhura; Perlis, Donald
    Artificial intelligence research falls roughly into two categories: formal and implementational. This division is not completely firm: there are implementational studies based on (formal or informal) theories (e.g., CYC, SOAR, OSCAR), and there are theories framed with an eye toward implementability (e.g., predicate circumscription). Nevertheless, formal/theoretical work tends to focus on very narrow problems (and even on very special cases of very narrow problems) while trying to get them ``right'' in a very strict sense, while implementational work tends to aim at fairly broad ranges of behavior but often at the expense of any kind of overall conceptually unifying framework that informs understanding. It is sometimes urged that this gap is intrinsic to the topic: intelligence is not a unitary thing for which there will be a unifying theory, but rather a ``society'' of subintelligences whose overall behavior cannot be reduced to useful characterizing and predictive principles. Here we describe a formal architecture that is more closely tied to implementational constraints than is usual for formalisms, and which has been used to solve a number of commonsense problems in a unified manner. In particular, we address the issue of formal, integrated, and longitudinal reasoning: inferentially-modeled behavior that incorporates a fairly wide variety of types of commonsense reasoning within the context of a single extended episode of activity requiring keeping track of ongoing progress, and altering plans and beliefs accordingly. Instead of aiming at optimal solutions to isolated, well-specified and temporally narrow problems, we focus on satisficing solutions to under-specified and temporally-extended problems, much closer to real-world needs. We believe that such a focus is required for AI to arrive at truly intelligent mechanisms with the ability to behave effectively over considerably longer time periods and range of circumstances than is common in AI today. While this will surely lead to less elegant formalisms, it also surely is requisite if AI is to get fully out of the blocks-world and into the real world. (Also cross-referenced as UMIACS-TR-99-65)
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    On Orthogonalization in the Inverse Power Method
    (1999-10-13) Stewart, G. W.
    When the inverse power method is used to compute eigenvectors of a symmetric matrix corresponding to close eigenvalues, the computed eigenvectors may not be orthogonal. The cure for the problem is to orthogonalize the vectors using the Gram--Schmidt algorithm. In this note it is shown that the orthogonalization process does not cause the quality of the eigenvectors to deteriorate. Also cross-referenced as UMIACS-TR-99-64