A processing unit for controlling a programmable electrical system of a building, said programmable electrical system comprising a plurality of addressable elements (10,12,14), the processing unit comprising: an interaction interface for receiving an input from a user to interact with a graphical user interface, said interaction interface being adapted for: - rendering a graphical map in said graphical user interface, on which graphical map said addressable elements (10,12,14) are represented, - graphically representing a plurality of locations (LOC1,LOC2) in said building by corresponding contours on said graphical map, - receiving an input from said user to add, remove and move a contour representative of a location (LOC1,LOC2) in said building on said graphical map using said graphical user interface, and - assigning a location (LOC1,LOC2) in the building, graphically represented on the graphical map by the corresponding contour, to an addressable element (10,12,14), and a storage memory for storing at least one data container, characterized in that non-intersecting closed contours are graphically representing the plurality of locations in said building in a single view on said graphical map, a location in the building, graphically represented on the graphical map by the corresponding contour, is logically assigned to an addressable element if a graphical representation of said addressable element is contained within the closed contour graphically representing said location on said graphical map, and the at least one data container comprises a definition of a location (LOC1,LOC2) in the building, of a closed contour associated with said location (LOC1,LOC2) in the building and of addressable elements (10,12,14) assigned to said location (LOC1,LOC2) in the building, wherein each data container of the at least one data container is an independently accessible and referenceable data object relating to a single, corresponding one location of said plurality of locations in the building and data associated with said location in the building. an interaction interface for receiving an input from a user to interact with a graphical user interface, said interaction interface being adapted for: - rendering a graphical map in said graphical user interface, on which graphical map said addressable elements (10,12,14) are represented, - graphically representing a plurality of locations (LOC1,LOC2) in said building by corresponding contours on said graphical map, - receiving an input from said user to add, remove and move a contour representative of a location (LOC1,LOC2) in said building on said graphical map using said graphical user interface, and - assigning a location (LOC1,LOC2) in the building, graphically represented on the graphical map by the corresponding contour, to an addressable element (10,12,14), - rendering a graphical map in said graphical user interface, on which graphical map said addressable elements (10,12,14) are represented, - graphically representing a plurality of locations (LOC1,LOC2) in said building by corresponding contours on said graphical map, - receiving an input from said user to add, remove and move a contour representative of a location (LOC1,LOC2) in said building on said graphical map using said graphical user interface, and - assigning a location (LOC1,LOC2) in the building, graphically represented on the graphical map by the corresponding contour, to an addressable element (10,12,14), and a storage memory for storing at least one data container, characterized in that non-intersecting closed contours are graphically representing the plurality of locations in said building in a single view on said graphical map, a location in the building, graphically represented on the graphical map by the corresponding contour, is logically assigned to an addressable element if a graphical representation of said addressable element is contained within the closed contour graphically representing said location on said graphical map, and the at least one data container comprises a definition of a location (LOC1,LOC2) in the building, of a closed contour associated with said location (LOC1,LOC2) in the building and of addressable elements (10,12,14) assigned to said location (LOC1,LOC2) in the building, wherein each data container of the at least one data container is an independently accessible and referenceable data object relating to a single, corresponding one location of said plurality of locations in the building and data associated with said location in the building.