In dynamic ubiquitous environments, end users may need to create services by causing two or more devices or resources to interoperate together in ad-hoc circumstances. In general, users can find this kind of process hard to manage. At the same time, existing UI architectures are not well suited to supporting such activities. It is proposed that a good basis for addressing these and related problems in a principled, scaleable way is the principle of Direct Combination (DC). The principle is summarized, and analytical arguments are presented that predict that DC can reduce the amount of search required by the user. Other things being equal, such a reduction in search would be expected to offer interactions which are faster, less frustrating, and impose less mental load on the user. We present a proof-of-concept implementation, and a small-scale evaluation of a DC interface. Within the limitations of a preliminary evaluation, consistent support is offered across several measures for the analytical predictions
