External Log In - Log a Customer in from another system

[designerman]

/includes/modules/pages/login/header_php.php
similar for logout

I've done a var_dump on the $_SESSION super global and it has opened some more questions,

Contents of the dump

array(18) {
["customers_host_address"]=> string(29) "XXXXXXXXX.XXX.XX"
["cartID"]=> string(0) ""
["cart"]=> &object(shoppingcart)(8)
{
["observers"]=> array(0) { }
["contents"]=> array(0) { }
["total"]=> int(0) ["weight"]=> int(0)
["content_type"]=> bool(false) ["free_shipping_item"]=> int(0) ["free_shipping_weight"]=> int(0)
["free_shipping_price"]=> int(0) }
["navigation"]=> &object(navigationhistory)(3) {
["observers"]=> array(0) { }
["path"]=> array(1) { [0]=> array(4) {
["page"]=> string(5) "login"
["mode"]=> string(6) "NONSSL"
["get"]=> array(1) { ["action"]=> string(7) "process" }
["post"]=> array(0) { }
}
}
["snapshot"]=> array(0) { }
}
["check_valid"]=> string(4) "true"
["language"]=> string(7) "english"
["languages_id"]=> string(1) "1"
["languages_code"]=> string(2) "en"
["currency"]=> string(3) "GBP"
["updateExpirations"]=> bool(true)
["session_counter"]=> bool(true)
["customers_ip_address"]=> string(14) "XXX.XXX.XXX.XX"
["customer_id"]=> string(1) "3"
["customer_default_address_id"]=> string(1) "3" ["customers_authorization"]=> string(1) "0"
["customer_first_name"]=> string(3) "Tom"
["customer_country_id"]=> string(3) "222"
["customer_zone_id"]=> string(3) "190"
}

Question being do I need to set all these session values or just the ones starting customers_ in order for a login to be "correct" in terms of the application being ok with it?

Thanks very much for any help