Abstract: Methods, including computer programs encoded on a computer storage medium, for improving database functionality. In one aspect, a method includes: in response to receiving a query for data associated with one or more properties, accessing listing information for multiple, different communities within which multiple, different types of properties are physically located; selecting, from among the different communities, a particular set of communities; determining that a value of one or more properties within the selected particular set of communities is missing or stale; obtaining an initial estimate of the value of one or more properties within the particular set of communities; defining a cost function that depends on a set of parameters, optimizing the cost function to generate a set of optimal parameters, and obtaining an updated estimate of the value of each property within the particular set of communities based on the generated set of optimal parameters.