has operator matches objects
that are tagged with the named tag. For instance,
matches all objects to which Alice has attached her
rating tag—all four objects in Figure A-1. Similarly,
would match only Led Zeppelin IV since that’s the only object to which Γλαύκων has attached a rating.
The value of the tag does not matter; even a tag with no value
will be matched by the
The values of any tag having a simple native type can be tested with an explicit query of the form
tag is the name of a tag and
value is a specification of a matching
In the case of numbers, the operator tests exact numeric equality, so that both
alice/rating = 5
alice/rating = 5.0
match any objects that Alice has tagged with a rating of 5 (or 5.0).
String values will not match these queries (for example, tags with textual
"5.0"). In Figure A-1 only the Led Zeppelin album,
IV, will match.
In the case of booleans (true/false values), the words
false will match, regardless of
alice/likes = true alice/likes = false
In the Figure A-1, only Emma will match the first query, and only Animal Farm will match the second query.
No numeric or textual values will ...