What is a pattern?

The goal of this paper is to give an introduction in a broad emerging area of software patterns, by presenting basic concepts of patterns in software, such as pattern template, pattern language, pattern system, and pattern catalog. Patterns are effective means of communication between software developers. Patterns, in a sense, help bring order into the chaos. Patterns represent best practice, proven solutions, and lessons learned, that aid in evolving software engineering into a mature engineering discipline. The aim is that every software developer should be able to use patterns when building software systems. Thus, to reach this aim, large pattern sets have to be presented in a form of languages, catalogs, systems, or even handbooks. The rest of the paper is organized as follows. In section 2 a definition and basic characteristics of a software pattern are given. Section 3 presents the classification of patterns in software, with the emphasis on design patterns. This is followed by description of the most common used templates for recording patterns in section 4, and different pattern collections in section 5. Paper finishes with the short history of software patterns, section 6.