Pattern-based machine translation systems can be easily customized by adding new patterns. To gain full profits from this character, input of patterns should be both expressive and simple to understand. The pattern-based machine translation system we have developed simplifies the handling of features in patterns by allowing sharing constraints between non-terminal symbols, and implementing an automated scheme of feature inheritance between syntactic classes. To avoid conflicts inherent to the pattern-based approach the system has priority control between patterns and between dictionaries. This approach proved its scalability in the web-based collaborative translation environment `Yakushite Net.'