Appendix A. Fluidinfo Query Language Reference

Tag Presence: The has Operator

The has operator matches objects that are tagged with the named tag. For instance,

has alice/rating

matches all objects to which Alice has attached her rating tag—all four objects in Figure A-1. Similarly,

has γλαύκων/rating

would match only Led Zeppelin IV since that’s the only object to which Γλαύκων has attached a rating.

Four Fluidinfo objects used to illustrate queries.
Figure A-1. Four Fluidinfo objects used to illustrate queries.


The value of the tag does not matter; even a tag with no value will be matched by the has operator.

Equality: The = Operator

The values of any tag having a simple native type can be tested with an explicit query of the form

tag = value

where tag is the name of a tag and value is a specification of a matching value.

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 values "5", "5.0"). In Figure A-1 only the Led Zeppelin album, IV, will match.

In the case of booleans (true/false values), the words true and false will match, regardless of capitalization:

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 ...

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