A system and method are disclosed that enable a personal shopping cart to be used to select items from multiple web sites of multiple business entities, and to place a single order for the selected items. The sling is operable by the lifting tower through a lifting range to move between positions in which a person carried in the sling is raised above the removable seat so that the removable seat may be removed and a person carried in the sling is lowered to be supported over the receptacle. The adapted topological query may be generated upon detecting a pre-specified sub-graph in the base topological query. In one approach, the controller receives a request to transfer data to a receiver. In particular, each rod segment of the ith of stage has a cross sectional radius ri, and a central axis located a distance Ri+ri from the guide axis.