declare function auth:login($login as xs:string, $pass as xs:string) as xs:string
{
	let $user := /buers/buyer[login=$login]
	return
	if($user)
	then
	(
		if($user/password=$pass)
		then
		(
			session:create(),
			session:set-attribute("login", $user/login),
			$login
		)
		else( "")
	)
	else
	(
		""
	)
};