Conceptual architecture is a form of architecture that utilizes conceptualism, characterized by an introduction of ideas or concepts from outside of architecture often as a means of expanding the discipline of architecture. This produces an essentially different kind of building than one produced by the widely held 'architect as a master-builder' model, in which craft and construction are the guiding principles. In conceptual architecture, the finished building as product is less important than the ideas guiding them, ideas represented primarily by texts, diagrams, or art installations. Architects that work in this vein are Diller + Scofidio, Bernard Tschumi, Peter Eisenman, and Rem Koolhaas.