Japan is currently facing some environment changes, like global competition, deregulations, highly developed information technology (IT), etc., so Japanese firms need to increase their productivity more than ever before and use flexible information systems to survive. Historically, the biggest challenge facing firms is "adaptation" to any environment. The flexibility of information systems to create business values has long been discussed as a critical problem among IT communities. One potential solution is to adopt a web service using service-oriented architecture (SOA). When SOA is adopted, an enterprise architecture (EA) viewpoint is crucial. We clarify the problems when firms implement SOA and discuss solutions from an EA viewpoint while also discussing the relation between EA and information systems on the basis of our factor analysis of the Japanese banking industry.