Wheeler proposed a curriculum model in 1967 that built upon Tyler's model by accounting for learning from both inside and outside the classroom. Wheeler's cyclic model includes 6 steps: 1) determining objectives, 2) selecting learning experiences, 3) selecting content, 4) organizing learning experiences, 5) evaluating learning, and 6) using evaluation results to refine objectives and restart the process. Unlike Tyler's linear model, Wheeler's model is cyclic with evaluation influencing future objectives and content selection. Both Tyler and Wheeler significantly contributed to the field of curriculum planning.