How should these filters work?

Question

I have a product page with product reviews which can be filtered. The top level filters are by review type: All, videos, product reviews and stories.

Product reviews and stories can then be filtered by subject type. How should the subject type filter work. For example if ALL is selected the subject filter only applies to Product reviews and stories. How do I show the filters only apply to two of the review types?

Answer 1

One idea is to group the child category filters below the parent category. This makes it clear that the child category filters will return a subset of the parent:

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This design gives you flexibility in the event that your taxonomy changes. For example if a new subject type is created for Product Reviews but not videos, you could add that in without having to make any changes to the control's logic.

Update

The more I have thought about it, the more I dislike having "All" as an option in the UI at all.

Marcos' question about faceted search made a good point:

...most of the websites use a set of check boxes, and the All function is done by checking all the boxes, eg. Kayak or Amazon do it like this.

With only 3 review types, it is fairly simple for a user to select 1, 2, or 3 options. As a result I'd instead use the following UI:

^{download bmml source}

Update 2 Incorporated kountor's excellent suggestion of pre-checking child categories.