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14. The Principle of Orthogonal Design > TUPLES vs. PROPOSITIONS
As we know, every tuple appearing in some given relvar R at some given time represents a certain proposition, the proposition in question being an instantiation of the relvar predicate for that relvar R that (by convention) is understood to be true at the time in question. For example, here again is the predicate for relvar HP from Figure 14-2 and Figure 14-3:
Part PNO is named PNAME, has color COLOR and weight WEIGHT (which is greater than or equal to 17.0), and is stored in city CITY.
This relvar contains (among other things) a tuple for part P6, and that tuple represents the following instantiation of the foregoing predicate:
Part P6 is named Cog, has color Red and weight 19.0 (which is greater than or equal to 17.0), and is stored in city London.
