Typically, sites that use faceted search support selecting only a single value or range for a given facet. Facet selections are encoded as hyperlinks, and when a user clicks a link to make a selection, a search query is issued that specifies that selection as a constraint. So, for example, for a color facet, when a customer clicks the link for the Red selection value, a search is issued and returns only items whose color value is Red.
Some sites use a different approach that allows the customer to make multiple selections for the same facet. Rather than encoding the selections as hyperlinks, each selection has an associated checkbox, and the user can choose multiple selections for a single facet. A separate button must be provided to issue the query once the selections are chosen, since the selections themselves are not hyperlinks.
If multiple facet values are selected, this should be reflected in the facet trail. You can specify multiple selections for a facet by separating them with the pipe (|) character. For example, if a user chooses the Red and Green selections for a color facet, the facet trail entry for this facet would look something like this:
3:Red|Green
