What would a HCI diagram look like

I dunno what type of diagram you mean...
maybe something like one of these?
http://www.google.com/imgres?q=Hcl+diagram&hl=en&client=firefox-a&hs=LQr&sa=X&rls=org.mozilla:en-US:official&tbm=isch&prmd=imvnsfd&tbnid=wMwBpb_RDTRyjM:&imgrefurl=http://etm523.blogspot.com/2009/09/team-delta-project-one-vinyl-chloride.html&docid=-eXuB0iSHABCcM&imgurl=http://z.about.com/d/chemistry/1/0/Y/o/Vinyl-chloride-2D.jpg&w=1097&h=974&ei=ZF3ETuOZIqPnsQLL24mSCw&zoom=1&iact=hc&vpx=600&vpy=140&dur=2571&hovh=212&hovw=238&tx=137&ty=78&sig=106299370676036167807&page=1&tbnh=133&tbnw=150&start=0&ndsp=11&ved=1t:429,r:3,s:0&biw=1047&bih=490

or maybe

http://www.google.com/imgres?q=Hcl+diagram&hl=en&client=firefox-a&hs=LQr&sa=X&rls=org.mozilla:en-US:official&tbm=isch&prmd=imvnsfd&tbnid=vjCdA2_fsir_xM:&imgrefurl=http://ths.sps.lane.edu/chemweb/unit9/tests/index.htm&docid=bQ6iOXhHNFCCIM&imgurl=http://ths.sps.lane.edu/chemweb/unit9/tests/HCl.gif&w=125&h=59&ei=ZF3ETuOZIqPnsQLL24mSCw&zoom=1&iact=hc&vpx=509&vpy=332&dur=2710&hovh=52&hovw=111&tx=71&ty=41&sig=106299370676036167807&page=1&tbnh=52&tbnw=111&start=0&ndsp=11&ved=1t:429,r:8,s:0&biw=1047&bih=490