title: Rest API multiple parameters
body: <p>I'm in the initial stages of planning a REST api.  I'm only interested in the read aspects of it for now.  I'm having trouble with filters.  As a hypothetical, this api is designed to serve "foo" products.  Each foo product can have one or more "bar" items, and one or more "baz" items.  The combination of foo/bar/baz is what makes the final product (and url) distinct, and is what I'm looking for.  The url must be bookmarkable, and able to recreate the final configured product.</p>
  
  <p>I considered <a href="https://stackoverflow.com/questions/9371195/rest-api-requesting-multiple-resources-in-a-single-get">this</a> answer, but while they suggest using query parameters as filters, it doesn't really address how to do so when more than one filter is needed.  Say, for example, I needed foo item "1", with bar items "1,3,4" and baz items "2,5".  What is the most proper construction for this sort of request?  I'm thinking 'foo/1/bar/1,3,4/baz/2,5' is problematic.  Is it perhaps 'foo/1/bar/baz?bar=1,3,4&amp;baz=2,5'? 'foo/1?bar=1,3,4&amp;baz=2,5'?  Do singletons all get to be part of the url, where multiples are relegated to the query parameters?</p>