Codes that attain minimum distance in every possible direction. Central European Journal of Mathematics. 2008;6(1):1-11. Abstract
Codes that attain minimum distance in every possible direction
The following problem motivated by investigation of databases is studied. Let C be a q-ary code of length n with the properties that C has minimum distance at least n – k + 1, and for any set of k – 1 coordinates there exist two codewords that agree exactly there. Let f(q, k) be the maximum n for which such a code exists. f(q, k) is bounded by linear functions of k and q, and the exact values for special k and q are determined.
Semantics in databases. In: Lecture notes in computer science. Vol 2582. Berlin: Springer; 2003. p. 1-6. Abstract
Semantics in databases
Semantics in databases: second international workshop, Dagstuhl Castle, Germany, January 7-12, 2001 : revised papers
Functional dependencies inpresence of errors. In: Eiter T, Schewe KD, editors. Foundations of Information and Knowledge Systems. Vol 2284. Berlin: Springer; 2002. (Lecture Notes in Computer Science; vol 2284).
Error-correcting keys in relational databases. In: Schewe KD, Thalheim B, editors. Foundations of Information and Knowledge Systems. Vol 1762. Berlin: Springer; 2000. p. 88-93. (Lecture Notes in Comput. Sci.; vol 1762). Abstract
Error-correcting keys in relational databases
Suppose that the entries of a relational database are collected in an unreliable way, that is the actual database may differ from the true database in at most one data of each individual. An error-correcting key is such a set of attributes, that the knowledge of the actual data of an individual in this set of attributes uniquely determines the individual. It is showed that if the minimal keys are of size at most ii, then the smallest sizes of the minimal error-correcting keys can be ck(3) and this is the best possible, all minimal error-correcting keys have size at most 3k(3).
Low discrepancy allocation of two-dimensional data. In: Schewe KD, Thalheim B, editors. Foundations of Information and Knowledge Systems. Vol 1762. Berlin: Springer; 2000. p. 1-12. Abstract
Low discrepancy allocation of two-dimensional data
Fast browsing and retrieval of geographically referenced information requires the allocation of data on different storage devices for concurrent retrieval. By dividing the two-dimensional space into tiles, a system can allow users to specify regions of interest using a query rectangle and then retrieving information related to tiles covered by the query. Suppose that there are m I/O devices. A tile is labeled by i if the data corresponding to this area is stored in the ith I/O device. A labeling is efficient if the difference of the numbers of occurrences of distinct labels in any given rectangle is small. Except for some simple cases this discrepancy exceeds i. In the present paper constructions are given to make this discrepancy small relative to m. The constructions use latin squares and a lower bound is given, which shows that the constructions are best possible under certain conditions.