論文アブストラクト：Traditional graphic design tools emphasize the grid for structuring layout. Interviews with professional graphic designers revealed that they use surprisingly sophisticated structures that go beyond the grid, which we call graphical substrates. We present a framework to describe how designers establish graphical substrates based on properties extracted from concepts, content and context, and use them to compose layouts in both space and time. We developed two technology probes to explore how to embed graphical substrates into tools. Contextify lets designers tailor layouts according to each reader's intention and context; while Linkify lets designers create dynamic layouts based on relationships among content properties. We tested the probes with professional graphic designers, who all identified novel uses in their current projects. We incorporated their suggestions into StyleBlocks, a prototype that reifies CSS declarations into interactive graphical substrates. Graphical substrates offer an untapped design space for tools that can help graphic designers generate personal layout structures.