Nowadays modern Web applications provide desktop-application-like flexible user experiences without using explicit requests. Modern Web applications need complex components: sever-side logic programs, server-side communication programs, output Web pages, client-side logic programs, and client-side communication programs. We present a new generation model called client-side centric model. This model allows us to define one-page modern Web applications dealing with databases easily. From GUI based declarative definitions, we can generate COMET technology based modern Web applications such as chat applications and calendar applications.