he lists a facet “flavours” such as cherry, chocolate, pecan. How is the flavour mixture “chocolate and pecan” to be handled? In a classified catalogue, the mixed flavour could be represented by linking the notations for the two flavours (e.g. cho-pec). This cannot be done on the Web, and Wilson rightly argues that to assign both terms to an entity at the classifying stage violates the principle that the terms in a facet should be mutually exclusive. Such an assignation at the search stage is better interpreted as a call for “chocolate OR pecan”.
One solution might be to include mixtures such as “chocolate/pecan” as terms in the flavours facet. I do not consider that this does violence to exclusivity—a mixture is a different flavour from its constituents, or why bother to provide it? Would we reject the term “sweet and sour” in Chinese cookery? An alternative solution is to add a term “mixed” in the flavours facet, and provide as a “subfacet” a checklist of the original flavours with the instruction “tick each flavour in the mixture”. Any combination could thus be constructed and used in classifying and search—though admittedly this would require programming beyond the basic facet