6.4. But what do these options do? Where do they live?

If you know Perl, you know what a hash reference is. An Interchange shopping cart consists of an array of hash references. If you dump the structure of the main shopping cart you would see something like:

        [
                {
                        mv_ip       => '0',
                        price_group => 'general',
                        mv_ib       => 'products',
                        code        => 'os28080',
                        quantity    => '1',
                },
                {
                        mv_ip       => '1',
                        price_group => 'general',
                        mv_ib       => 'products',
                        code        => 'os28080',
                        size        => 'L',
                        color       => 'black',
                        quantity    => '1',
                },
         ]

Each key of the hash is an attribute. There are a number of special attributes:

code The item SKU sku The SKU of the base item (in the case of matrix options) mv_ip The line number of the shopping cart (minus 1) mv_ib The database table the product was ordered from quantity The number on order group The order group for a master item or subitem mv_si Subitem indicator mv_mi Master item code mv_mp Modular item mv_price Price of the item (to directly set pricing) mv_order_route Special order route for this item

Any attribute besides the above is a product option or modifier, and can be displayed with [item-modifier attribute_name].