This study addresses building an interactive system that effectively prompts customers to make their decision while shopping online. It is especially targeted at purchasing as concept articulation where customers initially have a vague concept of what they want and then gradually clarify it in the course of interaction, which has not been covered by traditional online shopping systems. This paper proposes information presentation methods to effectively facilitate customers in their concept articulation process, and the framework for interaction design to enable the methods. Specifically, this study builds a system called S-Conart that facilitates purchasing as concept articulation through support for customers conception with spatial-arrangement style information presentation and for their conviction with scene information presentation, and then makes a set of evaluation experiments with the system to verify that the approach used in building the system is effective in facilitating the purchasing as concept articulation.