Service discovery is a crucial component of any serviceoriented
network. Discovery criteria depend on the underlying network and the application. In movement-assisted service delivery cases in WSAN, delivery distance is a primary concern for energy saving and timely response. This heralds the emergence of distance-sensitive service discovery. Here, distance sensitivity implies the closest or nearby service selection. Informally speaking, closest service
selection means that each service consumer discovers the
closest service provider, while nearby service selection
means that each service consumer discovers a service
provider that is at most twice as far as the closest. In
addition to the distance-sensitivity requirement, service
discovery must be conducted in an efficient way, i.e., with
constant per-node storage load and with no global
computation, for the resource constraints of WSAN.
Generic service discovery algorithms, e.g., [5], [7], [10],
[14], and adoptable techniques, e.g., [3], [11], [17], [19], [20],
have been proposed, each, however, with major weaknesses
in resource usage. None of them were developed with
distance-sensitivity in mind. They are not a good option for
distance-sensitive service discovery in WSAN. Specialized
and efficient solutions are needed.