This work does a detailed study aiming to increase the knowledge about Software Development Process (from technical to management questions). A systemic approach to these topics, seeking a rigorous and formal treatment of their concepts and definitions, is done and their essential and fundamental characteristics are raised and evaluated from a view of engineering and under the perspective of Essential Modeling. A Vocabulary is established aiming to formulate a language (basics of all discussion of this work) with the minimum of ambiguities. A Social-Technical Systems Modeling Structure is presented and an Essential Model to the Software Development Process is proposed. The use of the Modeling Structure in this work is evaluated and it is analyzed under the perspective of the Essential Model proposed. At last, suggestions to further works in research and experimentation are presented.