What Is Software Engineering?

Software engineering is a modeling activity. Software engineers deal with complexity through modeling, by focusing at any one time on only the relevant details and ignoring everything else. In the course of development, software engineers build many different models of the system and of the application domain.
 Software engineering is a problem-solving activity. Models are used to search for an acceptable solution. This search is driven by experimentation. Software engineers do not have infinite resources and are constrained by budget and deadlines. Given the lack of a fundamental theory, they often have to rely on empirical methods to evaluate the benefits of different alternatives.
 Software engineering is a knowledge acquisition activity. In modeling the application and solution domain, software engineers collect data, organize it into information, and formalize it into knowledge. Knowledge acquisition is not sequential, as a single piece of additional data can invalidate complete models.
 Software engineering is a rationale-driven activity. When acquiring knowledge and making decisions about the system or its application domain, software engineers also need to capture the context in which decisions were made and the rationale behind these decisions. Rationale information, represented as a set of issue models, enables software engineers to understand the implication of a proposed change when revisiting a decision.