The document discusses principles of materials design according to various experts including Tomlinson, Nunan, Hutchinson, and Waters. It states that while there is no universal set of principles, experts have proposed frameworks and guidelines. Nunan outlined six principles such as materials linking to curriculum and encouraging application of skills. Tomlinson proposed 16 principles including achieving impact, relevance, and accommodating learning styles. Hutchinson and Waters presented a seven-step model of needs analysis, syllabus, development, methodology, trials, evaluation and revision. The document concludes that materials writers claim to rely more on intuition than explicit principles.