A proper treatment of this complication calls for the conception of something slightly more general than a sign relation proper, namely, a sign relational complex. In effect, expressed in the roughest practical terms, this allows for missing data in the columns of the relational database table for the sign relation in question. Typically one operates on the default assumption that all of the roles of elementary sign relations are filled, but remains wary enough of the possible exceptions to deal with them on an ad hoc basis.