There are several curriculum models that are dependent on different perspectives, including whether they are subject-centered or student-centered, traditional or innovative, and structured in a linear or cyclic way. The four main categories of curriculum design are traditional, student-centered, critical, and structural models. Some examples of specific curriculum models are the Tyler model, Taba model, and Saylor and Alexander model. Curriculum models aim to guide teaching and learning to meet the needs of students and can be evaluated based on fundamental questions around purposes, experiences, organization, and outcomes.