Siriwardena, M., Rooke, J., Koskela, L., Kagioglou, M., Mcdermott, P., Sexton, M., & Aouad, G. (2008, January). Procurers, providers and users (PPU) : towards a meta-role model for conceptualising product-service in the built environment. Presented at Building Resilience BEAR 2008, Kandalama, Sri Lanka