Curriculum development is the steps and procedures that are taken by individuals to enact changes to what is taught in a learning environment. This is different from curriculum design which is how a person views the subject or concept of curriculum. First, a person needs to design or conceive the curriculum in their mind. Second, they use an existing development model to actually create the curriculum.
There are many different processes or models of developing curriculum. The various models are often put into two broad categories, which are the scientific and non-scientific approaches. Under each are several different models that meet 
The scientific approaches to developing curriculum get their name from being precise, detailed oriented, based on rational thinking, and rigid in structure. Common models that fall under this approach include Tyler model, Taba model, and the Backward-Design model. All of these models have goals and objectives that are measurable in that they can be observed. This emphasis on providing evidence is a hallmark of scientific approaches and is derived from an empirical worldview.
The non-scientific approaches focus on the subjective, aesthetic, and personal aspects of learning. Curriculum development models under this approach stress learner over evidence needed to prove the attainment of scientific objectives. Learning is a holistic experience that cannot be fragmented into discrete parts scientifically. This approach is derived from post-modern/existentialist thinking with the focus on the individual rather than the masses as in the scientific approach.
Most teachers are unfamiliar with non-scientific approaches to curriculum development because education today is focused on research-based scientific practices. One model under the non-scientific approach is the Deliberation model.
Which approach to consider and what model to use depends always on the goals of the institution and the needs of the student.