<Array>
	a			<Class>.

<ArrayItem>
	a			<Class>.

<inArray>
	a 			<Property>;
    <domain>    <Array>;
    <range>     <ArrayItem>.

<_index_>
	a    		<Property>;
    <domain>    <ArrayItem>;
    <range>     <integer>.
Listing 5. Creating abstract classes and properties for arrays.