2450884
Enabling routes as context in mobile services
With the continuing advances in wireless communications, geo-positioning, and portable electronics, an infrastructure is emerging that enables the delivery of on-line, location-enabled services to very large numbers of mobile users. A typical usage situation for mobile services is one characterized by a small screen and no keyboard, and by the service being only a secondary focus of the user. It is therefore particularly important to deliver the "right" information and service at the right time, with as little user interaction as possible. This may be achieved by making services context aware.
 Mobile users frequently follow the same route to a destination as they did during previous trips to the destination, and the route and destination are important aspects of the context for a range of services. This paper presents key concepts underlying a software component that discovers the routes of a user along with their usage patterns and that makes the accumulated routes available to services. Experiences from using the component with real GPS logs are reported.
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).
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.
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.
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.
5451193
ECOOP Workshop on Distributed Object Security
The purpose of this workshop was to provide a forum for discussion of security problems relating to distributed object-oriented programming environments. As object-oriented technology is becoming more widely deployed, security has become a pressing issue. Object-Oriented programming languages and object-based systems generally offer a convenient set of abstractions for security, such as strong typing, well-defined interfaces and encapsulation of data. However, they also introduce a number of new problems, such as deciding on the granularity of protection in fine-grained object systems and the possible ambiguities arising from polymorphism and dynamic binding, e.g., can a compromised class be substituted for a valid one.
16785661
Partial outsourcing: a new paradigm for access control
Various security models have been proposed in recent years for different purposes. Each of these aims to ease administration by introducing new types of security policies and models. This increases the complexity a system administrator is faced with. Ultimately, the resources expended in choosing amongst all of these models leads to less efficient administration.In this paper, we propose a new access control paradigm, which is already well established in virus and SPAM protection as partial delegation of administration to external expertise centres. Well-known vulnerabilities can be filtered out and known sources of attacks can be automatically blocked. We describe how partial outsourcing can be achieved in a secure way. A framework, which enables this process has already been developed.
16254824
Trust Propagation in Small Worlds
The possibility of a massive, networked infrastructure of diverse entities partaking in collaborative applications with each other increases more and more with the proliferation of mobile devices and the development of ad hoc networking technologies. In this context, traditional security measures do not scale well. We aim to develop trust-based security mechanisms using small world concepts to optimise formation and propagation of trust amongst entities in these vast networks. In this regard, we surmise that in a very large mobile ad hoc network, trust, risk, and recommendations can be propagated through relatively short paths connecting entities. Our work describes the design of trust-formation and risk-assessment systems, as well as that of an entity recognition scheme, within the context of the small world network topology.
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.
11578916
Adaptability in CORBA: the mobile proxy approach
Adaptability is one of the most important challenges in modern distributed systems. It may be defined as the ease with which a software application satisfies the different system constraints and the requirements of users and other applications. Adaptability is needed because distributed systems are inherently open, heterogeneous, and dynamic environments integrating a wide range of platforms, operating systems and applications from a number of different sources. We propose to use mobile proxies to provide adaptability in distributed applications integrated using the CORBA technology. Downloading stubs and skeletons at runtime allows the adaptation of either client or server interfaces as well as the protocol linking the two.