1. A method for processing data performed in a data processing system having a storage unit, comprising creating a spatial index having a tree structure comprising a leaf containing location information and attribute information other than the location information with respect to a plurality of objects to be searched, and storing the spatial index in the storage unit; and referring to the spatial index stored in the storage unit in response to an in input of a search request including location information and attribute information for searching the object to be searched under combined search conditions of spatial search condition based on the location information and attribute condition based on the attribute information, and extracting the object to be searched that agrees with the search request; wherein said referring to the spatial index for searching the object comprises: determining whether or not a pertinent geometry agrees with the spatial search condition of the spatial index for each object of the plurality of objects to be searched; and for each said object, if the pertinent geometry agrees with the spatial search condition of the spatial search index, obtaining at least one value of subsidiary attribute added to a record of the object; comparing the obtained value of subsidiary attribute added to the record of the object with the attribute condition of the spatial index to determine whether or not an attribute of the pertinent geometry agrees with the attribute condition of the spatial index; and if the attribute of the pertinent geometry agrees with the attribute condition of the spatial index, extracting the object as a searched result.