An adsorbent for HC in an exhaust gas is an agglomerate of double-structure particles, each of which includes an HC-adsorbing zeolite core, and a ceramic coat wrapping the zeolite core and having a plurality of through-pores communicating with a plurality of pores in the zeolite core. In an exemplary embodiment, each XML schema element and type is uniquely labeled, using distinguishing parameters such as namespace to create name parts like a Hashing code and suffixes in order to achieve unique mapping. A plurality of keys is created for defining the information. The rim channel includes a plurality of rim openings distributed evenly along the perimeter of the rim channel.