We introduce the notion of reverse-safe data structures. These are structures that prevent reconstruction they encode (i.e., cannot be easily reversed). A structure D is called z - when there exist at least datasets with same set answers as ones stored by . The main challenge to ensure stores many useful queries possible, constructed efficiently, and has size close original dataset it encodes. ...

Van Veelen and van der Weide (2008) in a recent paper provided some interesting new perspectives on the index number problem. However, the present paper argues that their definitions of a true index and an exact index are different from the standard definitions in the literature. The differences between the various approaches is explained in the present paper.

An innnite word x has nite index if the exponents of the powers of primitive words that are factors of x are bounded. F. Mignosi has proved that a Sturmian word has nite index if and only if the coeecients of the continued fraction development of its slope are bounded. Mignosi's proof relies on a delicate analysis of the approximation of the slope by rational numbers. We give here a proof based...