 After landowners had acquired of unimproved land in a city for residential development, the city was required by California law to prepare a general plan governing land use and the development of open-space land.In response, the city adopted zoning ordinances that placed the owners' property in a zone in which property may be devoted to one-family dwellings, accessory buildings, and open-space uses, with density restrictions permitting appellants to build between one and five single-family residences on their tract.The city expressed its intention to acquire the Agins parcel for open space, and actually commenced condemnation proceedings to take title to it.