centralized than in the past are labelled Distributed Information Systems (DIS).

In recent years we have seen a tremendous development of distributed information systems, both in terms of scale, as well as in terms of the types of distributed information systems, where classical approaches such as distributed and federated databases are complemented with Peer-to-Peer and Grid

. In this paper, we present two logics that allow for specifying distributed information systems, emphasizing communication among sites. The low-level logic D 0 offers features that are easy to implement but awkward to use for specification, while the high-level logic D 1 offers convenient

The design of distributed information systems tends to be complex and therefore error-prone. However, in the field of monolithic, i.e. non-distributed, information systems much has already been achieved, and by now, the principles of their design seem to be fairly well-understood. The past decade

-level functional partitioning. These partitions are mapped into information process-ing modules. The modules are assigned to nodes of the distributed information systems. A central role is assigned to modules that mediate between the users ' workstations and data re-sources. Mediators contain

Critical infrastructures provide services upon which society depends heavily; these applications are themselves dependent on distributed information systems for all aspects of their operation and so survivability of the information systems is an important issue. Fault tolerance is a key mechanism

We describe Freenet, an adaptive peer-to-peer network application that permits the publication, replication, and retrieval of data while protecting the anonymity of both authors and readers. Freenet operates as a network of identical nodes that collectively pool their storage space to store data files and cooperate to route requests to the most likely physical location of data. No broadcast search or centralized location index is employed. Files are referred to in a location-independent manner, and are dynamically replicated in locations near requestors and deleted from locations where there is no interest. It is infeasible to discover the true origin or destination of a file passing through the network, and difficult for a node operator to determine or be held responsible for the actual physical contents of her own node.

With increasing size and complexity of the implementations of information systems, it is necessary to use some logical construct (or architecture) for defining and controlling the interfaces and the integration of all of the components of the system. This paper defines information systems

Growth of distributed systems has attained unstoppable momentum. If we better understood how to think about, analyze, and design distributed systems, we could direct their implementation with more confidence.

Systems This thesis suggests a set of system characteristics to be used when evaluating or analyzing the IT security of a distributed information system. Each characteristic is meant to be considered in the evaluation of relevant distributed system components. This is considered to be the first