being语法问题

eastcreat

cooperative apartment houses have the peculiar distinction of [U][U]being dwellings that must also operate as businesses.[/U]
请问此句中BEING 做何解，为何不省略。不知能否总结一下BEING 的用法[em07]

tongxun

用做短语中的系词。比如，Things being as they are：事情既然如此。