We talk about a symbiotic computing and a concept of flexibility of a distributed system on a multi-agent system. A symbiotic computing is a new concept in the future computing model and ambient and social environments. We were proposing and showing a flexibility of a distributed system before this paper. The flexibility of computing system and logical model is a key concept of analysis, design and developping a system. The another and powerful flexible calculating model on mathematical is proposed as a fuzzy logic. A flexibility of a computing is realized with many methods. We developed an agent-based framework for flexible distributed systems named ADIPS which consists of distributed agent work places, agent repositories and support tools. Using this framework, we are designing adaptive web systems which cope with the diversification of user's accessing situations.