A subject-matter expert (SME) or domain expert is a person who is an expert in a particular area or topic. The term domain expert is frequently used in expert systems software development, and there the term always refers to the domain other than the software domain. A domain expert is a person with special knowledge or skills in a particular area of endeavor. An accountant is an expert in the domain of accountancy, for example. The development of accounting software requires knowledge in two different domains, namely accounting and software. Some of the development workers may be experts in one domain and not the other. SME should also have basic knowledge on other technical subjects.
In general, the term is used when developing materials (a book, an examination, a manual, etc.) about a topic, and expertise on the topic is needed by the personnel developing the material. For example, tests are often created by a team of psychometricians and a team of subject matter experts. The psychometricians understand how to engineer a test while the subject matter experts understand the actual content of the exam. Books, manuals, and technical documentation are developed by Technical writers and instructional designers in conjunctions with SMEs. Technical communicators interview SMEs to extract information and convert it into a form suitable for the audience. SMEs are often required to sign off on the documents or training developed, checking it for accuracy. SMEs are also necessary for the development of training materials.
In software engineering environments, the term is used to describe professionals with expertise in the field of application. The term "SME" also has a broader definition in engineering and high tech as one who has the greatest expertise in a technical topic. SMEs are often asked to review, improve, and approve technical work; to guide others; and to teach. According to Six Sigma, a Subject Matter Expert "exhibits the highest level of expertise in performing a specialized job, task, or skill of broad definition."
In Pharmaceuticals and Biotechnology areas, ASTM standard E 2500 specifies SMEs for various functions in project and process management. SME is defined as an individual who is an expert on that subject. In one project, there will be many SMEs who are experts on Air, Water, Utilities, process machines, process, packaging, storage, distribution and supply chain management, to name a few.
In software development, as in the development of "complex computer systems" (e.g., artificial intelligence, expert systems, control, simulation, or business software) a SME is a person who is knowledgeable about the domain being represented (but often not knowledgeable about the programming technology used to represent it in the system). The SME tells the software developers what needs to be done by the computer system, and how the SME intends to use it. The SME may interact directly with the system, possibly through a simplified interface, or may codify domain knowledge for use by knowledge engineers or ontologists. An SME is also involved in validating the resulting system. SME has formal meaning in certain contexts such as CMMs.
See also 
- Domain knowledge
- Expert system
- Knowledge Engineer
- Knowledge Engineering
- Subject matter expert Turing test
- System testing
- User Acceptance Testing
- User interface design
- A Domain Expert, 6/11/06
- Different Types of Systems Users, 2004, University of Calgary
- Bultman, Kuipers, Harmelen, 2005, Maintenance of KBS's by Domain Experts