Yuhei Akahoshi Koji Zettsu Yutaka Kidawara Katsumi Tanaka Structural Approach to Service Composition Based on Relational Model. 130-148 2011 EJC http://dx.doi.org/10.3233/978-1-60750-992-9-130 conf/ejc/2011 db/conf/ejc/ejc2011.html#AkahoshiZKT11