A new theoretical framework for the conceptual modeling of personalized and context-aware systems is described which supports specification of customization for individual users and analyzing the interaction between the domain context and functionality. An initial taxonomy of models is proposed based on the concept of personalized requirements. Two layers of human-centric models are proposed: an individual user characteristics layer for adaptation in assistive technology, learning and learning support systems and an individual values and personal goals layer to tailor applications to personal requirements. Practical application of the modeling framework is illustrated in a healthcare case study of a personalized, self-adaptive context-aware system.