The tree of life is currently an active object of research, though next to vertical gene transmission non vertical gene transfers proved to play a significant role in the evolutionary process. To overcome this difficulty, trees of life are now constructed from genes hypothesized vital, on the assumption that these are all transmitted vertically. This view has been challenged. As a frame for thi...

In the commonly adopted data models (as ins entity-relationship data model 111, for example) an attribute is a mapping between an entity set or a relationship set and a value set. The intension of a mapping property is given implicitly or explicitly in the data models, but the extension can be generally represented by the set I), as in the relational model. We propose an alternati...