1. A method, comprising: accessing, by a computer system, input data comprising: training data comprising a first plurality of data records, each of the first plurality of data records having numeric data values at least for first and second variables in a plurality of variables; and a second plurality of data records comprising at least a first not fully specified data record that does not include a first numeric data value for the first variable in the plurality of variables; generating, by the computer system and using the training data, a representation of a relationship between the first variable and at least the second variable in the plurality of variables; and obtaining, by the computer system and using the generated representation, at least the first numeric data value for the first variable in the first not fully specified data record.