We revisit the problem of synthesis of service composition in the context of service oriented architecture from a tree automata perspective. Comparing to existing finite state machine and graph-based approaches to the problem of service composition, tree automata offers a more flexible and faithful modeling of multi-input services and their admissible compositions. In our framework, tree automata is used to express both type signature constraints of individual services as well as constraints on the order in which services must be invoked. To synthesize service compositions, users may provide optional specifications on the desired composite service. The user specifications are also expressed as tree automata. We employ a combination of tree automata algorithms to compute the set of all possible valid service compositions which satisfy the user specifications.