Rules occupy a hazy area between data and procedure.
Like data, each rule in a rule-base is independent, and can be linked to other rules dynamically based on common values. Looking at it another way, both databases and procedures can be thought of as degenerate cases of rule-bases. A database is a collection of rules that have no action statements and only one set of conditions. A procedure is one big rule with many statements. Figure 1 illustrates the relationship between data, procedure and rules.