i'm having trouble with my dtd file. i'm writing this for an order form. the order form has a case color, amount of batteries, recharger, arms, camera, and speech. what i am trying to do is incorporate the length of the arms. i have arms representing the amount of arms the customer choose, and the arm length is for the length of each arm. but i'm not sure how to write it in the dtd file. here is my dtd file so far.
<?xml version="1.0"?>
<!DOCTYPE orders [
<! ELEMENT orders (order)>
<! ELEMENT order (case, batteries, recharger, arm, camera, speech)>
<! ELEMENT case (#PCDATA)>
<! ELEMENT batteries (#PCDATA)>
<! ELEMENT recharger (#PCDATA)>
<! ELEMENT arm (#PCDATA)>
<! ELEMENT camera (#PCDATA)>
<! ELEMENT speech (#PCDATA)>
]>
this is how i would like to arm and length to be when the xml file is displayed
<arm> 2
<length> 50 </length>
<length> 75 </length>
</arm>