Programming languages have evolved by becoming more abstract - one Assembler symbol represented a string of binary; one COBOL instruction represented a string of symbols. The next evolutionary step, to metacode, demands a change of database architecture, away from one that embeds structure and rules in the programs to one whose programs can read structure and rules from the database and process every type of data.

Relational databases comprise varying numbers of dissimilar tables with varying numbers of dissimilar columns. This makes it very difficult to write generic code that is capable of working with every type of data - the basis of truly reusable programs.

By contrast, associative databases store all types of data, and metadata as well, in the same simple, consistent form of items and links. This means that it is easy to write truly reusable programs using a form of abstract programming called metacode, which is part of the associative model. Sentences shows this in action.