Distributed Information System

Distributed Information System (DIS) is seen as a collection of autonomous in­formation systems which can collaborate with each other. This collaboration can be driven by requests for knowledge needed to predict what values should replace null values in missing or incomplete attributes. Any incompleteness in data can be seen either as the result of a partial knowledge about properties of objects stored in DIS or some attributes might be just hidden from users because of the security reason. Clearly, in the second case, we have to be certain that the missing values can not be predicted from the available data by chase, distributed chase or any other null value imputation method. Let us assume that an attributes d is hidden at one of the sites of Distributed information system, denoted by 5 and called a client. With a goal to reconstruct this hidden attribute, a request for a definition of this attribute can be sent by 5 to some of its remote sites. These definitions stored in a knowledge-base KB can be used by Chase al­gorithm to impute missing attribute values describing objects in S. In this paper we show how to identify these objects and what additional values in S have to be hidden from users to guarantee that initially hidden attribute values in S can not be properly predicted by Distributed Chase.

Distributed information system is a system that connects a number of information systems using network communication technology. Here we assume that these systems are autonomous and incomplete. Incompleteness is understood by al­lowing having the set   of the weighted attribute values as the value of the attribute.  In addition, we assume that the sum of these weights has to be equal one (1). The definition of  the  information system of type A and  the  Distributed Information System is a modification of  the definitions given by Rasin and  which is later used by RaS and Dardzinska in to talk about  the semantic inconsistencies among websites of the Distributed information system from the  from the point of view of query answering. The type A is introduced generally to monitor if the weights assigned to the values of attributes by  the Chase algorithm are equal to  or greater than A.

Questionnaire:

• Explain about the DIS?