This paper studies the descriptional complexity of multi-parallel grammars with respect to the number of nonterminals and selectors, and the length of these selectors. As a result, it proves that every recursively enumerable language is generated by a multi-parallel grammar with no more than seven nonterminals and four selectors of length five.

Protection of privacy in databases has become of increasing importance. While a number of techniques have been proposed to query databases while preserving privacy of individual records in the database, very little is done to define a measure on how much privacy is lost after statistical releases. We suggest a definition based on information theory. Intuitively, the privacy loss is proportional...