We may use an abbreviation to help us to construct bases quickly. Suppose that B is any base. Then B+ refers to all the elements in the base B possessing data; and the symbol '+' alone signifies all elements defined so far and possessing data. This facility is available for all of the commands listed at the beginning of the section. Note that when the form B+ is used, only the data-carrying constituents of the base are included. If B contains other bases, they are not included or searched in any way.