In this paper we give structural charaterizations for disjunctive and conjunctive hierarchical simple games by characterizing them as complete games with a unique shift-maximal losing and, respectively, shift-minimal winning coalitions. We prove canonical representation theorems for both types of hierarchical games and establish duality between them. We characterize those disjunctive and conjun...

In order to decide on advertisement fees for web servers, Naor and Pinkas introduced (threshold) metering schemes secure against coalitions of corrupt servers and clients. They show that one should be able to detect illegal behavior of clients, i.e., one needs to verify the shares received from clients. Most metering schemes do not offer this feature. But Ogata and Kurosawa pointed out a minor ...

A metering scheme is a method by which an audit agency is able to measure the interaction between servers and clients during a certain number of time frames. Naor and Pinkas 7] considered schemes in which any server is able to construct a cryptographically secure proof if and only if it has been visited by at least a number, say h, of clients in a given time frame. In this paper we construct me...

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This paper presents a new technique for information access based on a combination of Geographic Information Systems (GIS) and conceptual structures as modeled in relational concept analysis. It is based on the idea that traditional relational databases restrict their data types to linearly ordered scales. Since spatial data are not linearly ordered, they cannot be modeled directly in relational...

Data warehousing is an emergent important data management technology having a substantial impact on enterprise decision support and being used in many industries {recent estimates place the market size at $9 billion for 1997. Data warehouses are orders of magnitude larger than conventional databases and are typically subjected to a mix of complex, ad-hoc queries. These queries often access sign...

Padró and Sáez [PS] introduced the concept of a k-partite access structure for secret sharing and gave a complete characterization of ideal bipartite structures. We derive a necessary condition for ideal tripartite structures, which we conjecture is necessary for all k.

Spatial data are complex and have spatial components and uncertain properties. It is important to develop effective spatial and aspatial indexing techniques to facilitate spatial and/or aspatial querying for databases that deal with spatial &a. In this study we discuss a number of spatial index structures, such as Multi-level grid file (ML,GF), R-tree, and R*-tree, for spatial andor aspatial qu...

This paper presents a first step towards a security model that defines access control for logical document structures. This model benefits from roles to abstract from users and from security levels (classifications) that abstract from objects. The security levels are defined on top of a complex document structure which will be needed for real web applications. Since a user clearance for an oper...

We will present some ideas about sharing a secret in a monotonic access structure. We show the relations which occur between the method of encrypting a monotonic access structure with the use of basis sets or maximal unprivileged sets, and that based on a logical formula (used by Benaloh and Leichter in [1]). We will also give some facts connected with the problem of security, including the asp...