18405463
Using abstractions for spatio-temporal conceptual modeling
Conceptual data modeling for complex applications, such as multimedia and spatiotemporal applications, often results in large, complicated and difficult-to-comprehend diagrams. These diagrams frequently involve repetition of autonomous, semantically meaningful parts that capture similar situations and characteristics. By recognizing such parts and treating them as modeling units, it is possible to simplify the diagrams, as well as the conceptual modeling process. In this paper, based on requirements drawn from real applications, we present a set of modeling units that capture spatial, temporal, and spatiotemporal aspects. To facilitate the conceptual design process, these units are abbreviated in the conceptual diagrams by corresponding spatial, temporal, and spatiotemporal modeling abstractions. The result is more elegant and less-detailed diagrams that are easier to comprehend (for the user) and to construct (for the designer), hut yet semantically rich. An extension of the Entity-Relationship model serves as the context for this study. An example from a real cadastral application illustrates the benefits of using an abstraction-based conceptual model.
45102117
Temporal specialization
The authors explore a variety of temporal relations with specialized relationships between transaction and valid time. An example is a retroactive temporal event relation, where the event must have occurred before it was stored, i.e., the valid time-stamp is restricted to be less than the transaction time-stamp. The authors discuss many useful restrictions, defining a large number of specialized types of temporal relations, and indicate some of their applications. A detailed taxonomy of specialized temporal relations is presented. This taxonomy may be used during database design to specify the particular time semantics of temporal relations.<<ETX>>
1655888
Supporting imprecision in multidimensional databases using granularities
Online analytical processing (OLAP) technologies are being used widely, but the lack of effective means of handling data imprecision, which occurs when exact values are not known precisely or are entirely missing, represents a major obstacle in applying these technologies in many domains. The paper develops techniques for handling imprecision that aim to maximally reuse existing OLAP modeling constructs such as dimension hierarchies and granularities. With imprecise data available in the database, queries are tested to determine whether or not they may be answered precisely given the available data; if not, alternative queries unaffected by the imprecision are suggested. When processing queries affected by imprecision, techniques are proposed that take into account the imprecision in the grouping of the data, in the subsequent aggregate computation, and in the presentation of the imprecise result to the user. The approach is capable of exploiting existing OLAP query processing techniques such as pre-aggregation, yielding an effective approach with low computational overhead and that may be implemented using current technology.
1348801
Using differential technlques to efficiently support transaction time
We present an architecture for query processing in the relational model extended with transaction time. The architecture integrates standard query optimization and computation techniques with new differential computation techniques. Differential computation computes a query incrementally or decrementally from the cahced and indexed results of previous computations. The use of differential computation techniques is essential in order to provide efficient processing of queries that access very large temporal relations. Alternative query plans are integrated into a state transition network, where the state space includes backlogs of base relations, cached results from previous computations, a cache index, and intermediate results; the transitions include standard relational algebra operators, operators for constructing differential files, operators for differential computation, and combined operators. A rule set is presented to prune away parts of state transition networks that are not promising, and dynamic programming techniques are used to identify the optimal plans from the remaining state transition networks. An extended logical access path serves as a “structuring” index on the cached results and contains, in addition, vital statistics for the query optimization process (including statistics about base relations, backlogs, and queries-previously computed and cached, previously computed, or just previously estimated).
1723263
Multidimensional data modeling for location-based services
Abstract.With the recent and continuing advances in areas such as wireless communications and positioning technologies, mobile, location-based services are becoming possible.Such services deliver location-dependent content to their users. More specifically, these services may capture the movements and requests of their users in multidimensional databases, i.e., data warehouses, and content delivery may be based on the results of complex queries on these data warehouses. Such queries aggregate detailed data in order to find useful patterns, e.g., in the interaction of a particular user with the services.The application of multidimensional technology in this context poses a range of new challenges. The specific challenge addressed here concerns the provision of an appropriate multidimensional data model. In particular, the paper extends an existing multidimensional data model and algebraic query language to accommodate spatial values that exhibit partial containment relationships instead of the total containment relationships normally assumed in multidimensional data models. Partial containment introduces imprecision in aggregation paths. The paper proposes a method for evaluating the imprecision of such paths. The paper also offers transformations of dimension hierarchies with partial containment relationships to simple hierarchies, to which existing precomputation techniques are applicable.
44396365
Specification-based data reduction in dimensional data warehouses
Presents a powerful and easy-to-use technique for aggregation-based data reduction that enables the gradual change of the data from being detailed to being increasingly aggregated. The technique enables huge storage gains while retaining the data that is essential to the users, and it preserves the ability to query original and reduced data in an integrated manner.
14855051
Mutual Suspicion in a Generic Object-Support System
We are currently facing the security paradox that applications must allow integration of information from various sources (like the web) and support global co-operation between users, i.e. there is a drive towards a stronger integration of information and services from weakly authenticated sources. In large networks like the Internet or enterprise wide intranets, without a common trusted computing base and no single source of authority in the system, a policy of mutual suspicion seems a prudent approach to co-operation.
7607582
Trust enhanced ubiquitous payment without too much privacy loss
Computational models of trust have been proposed for use in ubicomp environments for deciding whether to allow customers to pay with an e-purse or not. In order to build trust in a customer, a means to link transactions using the same e-purse is required. Roughly, trust is a result of knowledge. As the number of transactions increases, the resulting increase in knowledge about the user of the e-purse threatens privacy due to global profiling. We present a scheme (and its prototype) that mitigates this loss of privacy without forbidding the use of trust for smoothing payment by giving the opportunity to the user to divide trust (i.e. transactions) according to context (e.g. location, user's current activity or subset of shops).
15628651
Experience in Discovering , Modeling , and Reenacting Open Source Software Development Processes
Process discovery has been shown to be a challenging problem offering limited results. This paper describes a new approach to process discovery that examines the Internet information spaces of open source software development projects. In particular, we examine challenges, strengths, weaknesses and findings when seeking to discover, model, and reenact processes associated with large, global OSSD projects like NetBeans.org. The longer-term goal of this approach is to determine the requirements and design of more fully integrated process discovery and modeling mechanisms that can be applied to Web-based, open source software development projects.
2817831
Proper Actions of Automorphism Groups of Free Products of Finite Groups
If G is a free product of finite groups, let ΣAut1(G) denote all (necessarily symmetric) automorphisms of G that do not permute factors in the free product. We show that a McCullough–Miller and Gutierrez–Krstic derived (also see Bogley–Krstic) space of pointed trees is an $\underline{E} \Sigma {\rm Aut}_1(G)$-space for these groups.
2014239
Process modeling across the web information infrastructure
Web-based open source software development (OSSD) project communities provide interesting and unique opportunities for software process modeling and simulation. While most studies focus on analyzing processes in a single organization, we focus on modeling software development processes both within and across three distinct but related OSSD project communities: Mozilla, a Web artifact consumer; the Apache HTTP server that handles the transactions of Web artifacts to consumers such as the Mozilla browser; and NetBeans, a Java-based integrated development environment (IDE) for creating Web artifacts and application systems. In this article, we look at the process relationships within and between these communities as components of a Web information infrastructure. We employ expressive and comparative techniques for modeling such processes that facilitate and enhance understanding of the software development techniques utilized by their respective communities and the collective infrastructure in creating them. Copyright © 2005 John Wiley & Sons, Ltd.