Abstract:People use external knowledge representations (KRs) to create, identify, depict, transform, store, share, and archive information. Learning to work with KRs is central to becoming proficient in virtually every discipline. As such, KRs play central roles in curriculum, instruction, and assessment. We describe five key roles of KRs in assessment:1. An assessment is itself a KR, which makes explicit the knowledge that is valued, ways it is used, and standards of good work.2. The analysis of any domain in which learning is to be assessed must include the identification and analysis of the KRs in that domain.3. Assessment tasks can be structured around the knowledge, relationships, and uses of domain KRs.4. "Design KRs" can be created to organize knowledge about a domain in forms that support the design of assessment.5. KRs in the discipline of assessment design can guide and structure domain analyses (re #2), task construction (re #3), and the creation and use of design KRs (re #4).The third and fourth roles are developed in greater detail, through an "evidence-centered" design perspective that reflects the fifth role. Recurring implications of technology that leverage the impact of KRs in assessment are highlighted, including task design supports and automated task construction and scoring. Ideas are illustrated with "generate examples" tasks and simulation tasks for computer network design and troubleshooting.