Abstract: Abstract Dimension-and-Tolerance (D & T) models are crictical for the information completeness of product models and dimension-driven design. Existing D & T models are more or less versions of dimensioning of conventional drawings, and should be based on a sound design process theory. In this paper, the relationship of dimensions, constraints and design intent are discussed. A new D & T model (namely, SEDT model) based on feature semantics is proposed. SEDT is promising in analogical design and conceptual design. Dimension pattern, constraint pattern and related applications are also introduced.