1. A method comprising: by one or more computing devices, receiving a request for a property of an object, wherein: the property has a property type and comprises a property value and a property name; and the property does not conform to a property specification for the property type; by one or more computing devices, determining a field mapping for the property of the object, wherein the field mapping is derived from the property specification; by one or more computing devices, accessing the property of the object; by one or more computing devices, modifying the property of the object according to the field mapping; and by one or more computing devices, providing as a response to the request the property of the object as modified according to the field mapping.