Generic attributes are name-value pairs associated with a city object. Each generic attribute has a mandatory name identifier which can be freely chosen. The data type of the attribute value may be String, Integer, Double (floating point number), URI, Date, and gml:MeasureType. The attribute type is defined by the selection of the particular subclass of _genericAttribute, for example stringAttribute, intAttribute, etc. A measureAttribute facilitates the representation of measured values. Its value is of the structured type gml:MeasureType which provides an optional attribute uom (units of measure) of type xs:anyURI that points to a reference system for the amount.