求翻译：我国从1999开始，就已经开始制度实施城镇廉租住房保障制度，时至今日，城镇廉租住房保障制度已经更新换代3次，以此来不断适应社会发展的需要，是什么意思？

China from 1999, has begun implementation of the Scheme of urban housing security system, to date, urban housing security system replacement three times, in order to continue to adapt to the needs of social development,

From 1999 onwards, the town has already begun implementation of the system low-rent housing security system to this day, cities and towns, low-rent housing security system has been updated 3 times, and for generations to adapt to the needs of social development.

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Our country from 1999 starts, already started the system to implement the cities to rent the housing safeguard system inexpensively, at this point, the cities rented the housing safeguard system inexpensively already the renewal 3 times, met the social development need unceasingly by this,