IndexDefinition

What an index is over.

A path and a kind, and nothing else — no name, no options, no build state. Everything else about an index is either derived from the segments (its coverage) or assigned when it is created (its id), and putting any of it here would make two definitions of the same thing unequal.

The path is a CatalogPath rather than a VariantPath because that is the vocabulary the recommendation arrives in, and because it is the one that can describe an array: $.tags[*] indexes every element of tags, which is what a query asking "which documents are tagged x" means. A VariantPath names one location and cannot say that.