Resilient is a trait of any complex element-- often identified as an agent or resource-- which can temporarily adapt to highly variable conditions within a specific context and either (1) retain their specified functions during the period of temporary adaptation, or (2) return to their specified functions after disruption.
Resilience emerges from availability, adaptability, replaceability and reversibility. (Note that this is a placeholder addition, to be expanded later.)
robust: A specific element may be robust and resilient in varied contexts, including different hierarchical levels within a basic context.