Ralph Tyler's curriculum model is a linear model consisting of 4 steps: 1) defining learning objectives based on students, society, and subject matter experts, 2) selecting learning experiences to meet the objectives, 3) organizing learning experiences for maximum effect, and 4) evaluating if the objectives were met. The model emphasizes clear, measurable objectives and uses evaluation to improve the curriculum. It provides an easy guide for planning but lacks flexibility and fails to consider changes in learning contexts over time.