Hello.
In large Omeka installations, it is sometime useful to be able to find Items that have not Tags associated.
It seems there’s no way through the Advanced Search to accomplish that, unless by using a workaround: in the Advanced Search’s query string, replacing “Tags=” with “excludeTags=%” does the trick (excludeTags seems to be an option available for the API, but it can be used also this way).
I think it could be very useful if an extra Advanced Search parameter, a boolean hasTag, that could be used to find all Items that have or have not tags associated, was coded into the Omeka core files. The Advanced Search form should then include an extra option, to select that value.