systems engineering Systems engineering is an interdisciplinary field of engineering and engineering management that focuses on how to design, integrate, and manage complex systems over their life cycles. At its core, systems engineering utilizes systems thinking ...

software engineering Software engineering is a systematic engineering approach to software development. A software engineer is a person who applies the principles of software engineering to design, develop, maintain, test, and evaluate computer software. The term ' ...

, and

computer science Computer science is the study of computation, automation, and information. Computer science spans theoretical disciplines (such as algorithms, theory of computation, information theory, and automation) to practical disciplines (includin ...

, a function model or functional model is a structured representation of the functions ( activities, actions,

process A process is a series or set of activities that interact to produce a result; it may occur once-only or be recurrent or periodic. Things called a process include: Business and management *Business process, activities that produce a specific se ...

es,

operation Operation or Operations may refer to: Arts, entertainment and media * ''Operation'' (game), a battery-operated board game that challenges dexterity * Operation (music), a term used in musical set theory * ''Operations'' (magazine), Multi-Man ...

s) within the modeled system or subject area.FIPS Publication 183
released of IDEFØ December 1993 by the Computer Systems Laboratory of the National Institute of Standards and Technology (NIST). IDEF Diagram Example

A function model, similar with the

activity model In systems engineering, software engineering, and computer science, a function model or functional model is a structured representation of the functions ( activities, actions, processes, operations) within the modeled system or subject area.

process model The term process model is used in various contexts. For example, in business process modeling the enterprise process model is often referred to as the ''business process model''. Overview Process models are processes of the same nature that ar ...

, is a graphical representation of an

enterprise Enterprise (or the archaic spelling Enterprize) may refer to: Business and economics Brands and enterprises * Enterprise GP Holdings, an energy holding company * Enterprise plc, a UK civil engineering and maintenance company * Enterprise ...

's function within a defined scope. The purposes of the function model are to describe the functions and processes, assist with discovery of information needs, help identify opportunities, and establish a basis for determining product and service costs.Reader's Guide to IDEF0 Function Models
Accessed 27 Nov 2008.

History

The function model in the field of systems engineering and software engineering originates in the 1950s and 1960s, but the origin of functional modelling of organizational activity goes back to the late 19th century. In the late 19th century the first diagrams appeared that pictured business activities, actions, processes, or operations, and in the first half of the 20th century the first structured methods for documenting business process activities emerged. One of those methods was the

flow process chart The flow process chart is a graphical and symbolic representation of the activities performed on the work piece during the operation in industrial engineering. History The first structured method for documenting process flow, e.g., in flow sh ...

, introduced by

Frank Gilbreth Frank Bunker Gilbreth (July 7, 1868 – June 14, 1924) was an American engineer, consultant, and author known as an early advocate of scientific management and a pioneer of time and motion study, and is perhaps best known as the father and ce ...

to members of

American Society of Mechanical Engineers The American Society of Mechanical Engineers (ASME) is an American professional association that, in its own words, "promotes the art, science, and practice of multidisciplinary engineering and allied sciences around the globe" via "continuing ...

(ASME) in 1921 with the presentation, entitled “Process Charts—First Steps in Finding the One Best Way”.Ben B. Graham (2002). ''Detail Process Charting''. p.2. Gilbreth's tools quickly found their way into

industrial engineering Industrial engineering is an engineering profession that is concerned with the optimization of complex processes, systems, or organizations by developing, improving and implementing integrated systems of people, money, knowledge, information an ...

curricula. The emergence of the field of ''systems engineering'' can be traced back to

Bell Telephone Laboratories Nokia Bell Labs, originally named Bell Telephone Laboratories (1925–1984), then AT&T Bell Laboratories (1984–1996) and Bell Labs Innovations (1996–2007), is an American industrial Research and development, research and scientific developm ...

in the 1940s. The need to identify and manipulate the properties of a system as a whole, which in complex engineering projects may greatly differ from the sum of the parts' properties, motivated various industries to apply the discipline. One of the first to define the function model in this field was the British engineer William Gosling. In his book ''The design of engineering systems'' (1962, p. 25) he stated: :''A functional model must thus achieve two aims in order to be of use. It must furnish a throughput description mechanics capable of completely defining the first and last throughput states, and perhaps some of the intervening states. It must also offer some means by which any input, correctly described in terms of this mechanics, can be used to generate an output which is an equally correct description of the output which the actual system would have given for the input concerned. It may also be noted that there are two other things which a functional model may do, but which are not necessary to all functional models. Thus such a system may, but need not, describe the system throughputs other than at the input and output, and it may also contain a description of the operation which each element carries out on the throughput, but once again this is not.'' One of the first well defined function models, was the

functional flow block diagram A functional flow block diagram (FFBD) is a multi-tier, time-sequenced, step-by-step flow diagram of a system’s functional flow. The term "functional" in this context is different from its use in functional programming or in mathematics, where ...

(FFBD) developed by the defense-related TRW Incorporated in the 1950s. In the 1960s it was exploited by the

NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeedi ...

to visualize the time sequence of events in a space systems and flight missions. It is further widely used in classical

to show the order of execution of system functions.Thomas Dufresne & James Martin (2003)
"Process Modeling for E-Business"
. INFS 770 Methods for Information Systems Engineering: Knowledge Management and E-Business. Spring 2003

Functional modeling topics

Functional perspective

and

a function model is created with a functional

modeling perspective A modeling perspective in information systems is a particular way to represent pre-selected aspects of a system. Any perspective has a different focus, conceptualization, dedication and visualization of what the model is representing. The traditi ...

. The functional perspective is one of the perspectives possible in

business process modelling Business process modeling (BPM) in business process management and systems engineering is the activity of representing processes of an enterprise, so that the current business processes may be analyzed, improved, and automated. BPM is typically p ...

, other perspectives are for example behavioural, organisational or informational. A functional modeling perspective concentrates on describing the dynamic process. The main concept in this modeling perspective is the process, this could be a function, transformation, activity, action, task etc. A well-known example of a modeling language employing this perspective is

data flow diagram A data-flow diagram is a way of representing a flow of data through a process or a system (usually an information system). The DFD also provides information about the outputs and inputs of each entity and the process itself. A data-flow diagram ha ...

s. The perspective uses four symbols to describe a process, these being: *Process: Illustrates transformation from input to output. *Store: Data-collection or some sort of material. *Flow: Movement of data or material in the process. *External Entity: External to the modeled system, but interacts with it. Now, with these symbols, a process can be represented as a network of these symbols. This decomposed process is a DFD, data flow diagram. Fo2ufg823rhf832hfdorfg

In Dynamic Enterprise Modeling a division is made in the

Control model Control may refer to: Basic meanings Economics and business * Control (management), an element of management * Control, an element of management accounting * Comptroller (or controller), a senior financial officer in an organization * Controlling ...

, Function Model,

Process model The term process model is used in various contexts. For example, in business process modeling the enterprise process model is often referred to as the ''business process model''. Overview Process models are processes of the same nature that ar ...

and

Organizational model An organization or organisation (Commonwealth English; see spelling differences), is an entity—such as a company, an institution, or an association—comprising one or more people and having a particular purpose. The word is derived from ...

Functional decomposition

Functional decomposition In mathematics, functional decomposition is the process of resolving a functional relationship into its constituent parts in such a way that the original function can be reconstructed (i.e., recomposed) from those parts by function composition. ...

refers broadly to the process of resolving a

functional Functional may refer to: * Movements in architecture: ** Functionalism (architecture) ** Form follows function * Functional group, combination of atoms within molecules * Medical conditions without currently visible organic basis: ** Functional s ...

relationship into its constituent parts in such a way that the original function can be reconstructed from those parts by

function composition In mathematics, function composition is an operation that takes two functions and , and produces a function such that . In this operation, the function is applied to the result of applying the function to . That is, the functions and ...

. In general, this process of decomposition is undertaken either for the purpose of gaining insight into the identity of the constituent components, or for the purpose of obtaining a compressed representation of the global function, a task which is feasible only when the constituent processes possess a certain level of ''modularity''.

has a prominent role in

computer programming Computer programming is the process of performing a particular computation (or more generally, accomplishing a specific computing result), usually by designing and building an executable computer program. Programming involves tasks such as anal ...

, where a major goal is to ''modularize'' processes to the greatest extent possible. For example, a library management system may be broken up into an inventory module, a patron information module, and a fee assessment module. In the early decades of computer programming, this was manifested as the "art of subroutining," as it was called by some prominent practitioners. Functional decomposition of engineering systems is a method for analyzing engineered systems. The basic idea is to try to divide a system in such a way that each block of the block diagram can be described without an "and" or "or" in the description. This exercise forces each part of the system to have a pure

function Function or functionality may refer to: Computing * Function key, a type of key on computer keyboards * Function model, a structured representation of processes in a system * Function object or functor or functionoid, a concept of object-orie ...

. When a system is composed of pure functions, they can be reused, or replaced. A usual side effect is that the interfaces between blocks become simple and generic. Since the interfaces usually become simple, it is easier to replace a pure function with a related, similar function.

Functional modeling methods

The functional approach is extended in multiple diagrammic techniques and modeling notations. This section gives an overview of the important techniques in chronological order.

Function block diagram

functional block diagram A functional block diagram, in systems engineering and software engineering, is a block diagram. It describes the functions and interrelationships of a system. The functional block diagram can picture: * Functions of a system pictured by block ...

is a

block diagram A block diagram is a diagram of a system in which the principal parts or functions are represented by blocks connected by lines that show the relationships of the blocks.

, that describes the functions and interrelationships of a system. The functional block diagram can picture: * Functions of a system pictured by blocks * Input of a block pictured with lines, and * Relationships between 9 functions * Functional sequences and paths for matter and or signals The block diagram can use additional schematic symbols to show particular properties. Specific function block diagram are the classic

, and the

Function Block Diagram The Function Block Diagram (FBD) is a graphical language for programmable logic controller design, that can describe the function between input variables and output variables. A function is described as a set of elementary blocks. Input and out ...

(FBD) used in the design of programmable logic controllers.

Functional flow block diagram

The

(FFBD) is a multi-tier, time-sequenced, step-by-step

flow diagram Flow diagram is a collective term for a diagram representing a flow or set of dynamic relationships in a system. The term flow diagram is also used as a synonym for flowchart, and sometimes as a counterpart of the flowchart.Harris. (1999, p. 156 ...

of the system’s functional flow.The first version of this article is completely based on th
NAS SYSTEM ENGINEERING MANUAL SECTION
4.4 VERSION 3.1 06/06/06. The diagram is developed in the 1950s and widely used in classical

. The functional flow block diagram is also referred to as ''Functional Flow Diagram'', ''functional block diagram'', and ''functional flow''.Task Analysis Tools Used Throughout Development
FAA 2008. Retrieved 25 Sept 2008. Functional flow block diagrams (FFBD) usually define the detailed, step-by-step operational and support sequences for systems, but they are also used effectively to define

es in developing and producing systems. The

software development process In software engineering, a software development process is a process of dividing software development work into smaller, parallel, or sequential steps or sub-processes to improve design, product management. It is also known as a software deve ...

es also use FFBDs extensively. In the system context, the functional flow steps may include combinations of

hardware Hardware may refer to: Technology Computing and electronics * Electronic hardware, interconnected electronic components which perform analog or logic operations ** Digital electronics, electronics that operate on digital signals *** Computer hard ...

software Software is a set of computer programs and associated software documentation, documentation and data (computing), data. This is in contrast to Computer hardware, hardware, from which the system is built and which actually performs the work. ...

personnel Employment is a relationship between two parties regulating the provision of paid labour services. Usually based on a contract, one party, the employer, which might be a corporation, a not-for-profit organization, a co-operative, or any ot ...

, facilities, and/or procedures. In the FFBD method, the functions are organized and depicted by their logical order of execution. Each function is shown with respect to its logical relationship to the execution and completion of other functions. A node labeled with the function name depicts each function. Arrows from left to right show the order of execution of the functions. Logic symbols represent sequential or parallel execution of functions.FAA (2006)
NAS SYSTEM ENGINEERING MANUAL SECTION
4.4 VERSION 3.1 06/06/06.

HIPO and oPO

HIPO The term Hipo may refer to: * Hippopotamus * Hilfspolizei, an auxiliary police force * HIPO model, a 1970s tool for planning and documenting a computer program * 289 HiPo, a Ford Windsor engine * HIPO Corps, a Danish auxiliary police corps establi ...

for ''hierarchical input process output'' is a popular 1970s

systems analysis Systems analysis is "the process of studying a procedure or business to identify its goal and purposes and create systems and procedures that will efficiently achieve them". Another view sees system analysis as a problem-solving technique tha ...

design aid and documentation technique for representing the modules of a system as a

hierarchy A hierarchy (from Greek: , from , 'president of sacred rites') is an arrangement of items (objects, names, values, categories, etc.) that are represented as being "above", "below", or "at the same level as" one another. Hierarchy is an important ...

and for documenting each module.Sandia National Laboratories (1992)
Sandia Software Guidelines Volume 5 Tools, Techniques,and Methodologies
SANDIA REPORTS 85–2348qUC–32 It was used to develop requirements, construct the design, and support implementation of an expert system to demonstrate automated rendezvous. Verification was then conducted systematically because of the method of design and implementation. The overall design of the system is documented using HIPO charts or

structure chart A structure chart (SC) in software engineering and organizational theory is a chart which shows the breakdown of a system to its lowest manageable levels.IRS (2008) "Configuration Management" In: ''IRS Resources Part 2. Information Technology Cha ...

s. The structure chart is similar in appearance to an organizational chart, but has been modified to show additional detail. Structure charts can be used to display several types of information, but are used most commonly to diagram either

data structure In computer science, a data structure is a data organization, management, and storage format that is usually chosen for Efficiency, efficient Data access, access to data. More precisely, a data structure is a collection of data values, the rel ...

s or code structures.

N² Chart

The N² Chart is a diagram in the shape of a

matrix Matrix most commonly refers to: * ''The Matrix'' (franchise), an American media franchise ** '' The Matrix'', a 1999 science-fiction action film ** "The Matrix", a fictional setting, a virtual reality environment, within ''The Matrix'' (franchi ...

, representing functional or physical interfaces between system elements. It is used to systematically identify, define, tabulate, design, and analyze functional and physical interfaces. It applies to system

interface Interface or interfacing may refer to: Academic journals * ''Interface'' (journal), by the Electrochemical Society * '' Interface, Journal of Applied Linguistics'', now merged with ''ITL International Journal of Applied Linguistics'' * '' Int ...

s and

and/or

interfaces. The N² diagram has been used extensively to develop data interfaces, primarily in the

areas. However, it can also be used to develop hardware interfaces. The basic N² chart is shown in Figure 2. The system functions are placed on the diagonal; the remainder of the squares in the N × N matrix represent the interface inputs and outputs. NASA (1995). "Techniques of Functional Analysis". In:
NASA Systems Engineering Handbook
'' June 1995. p.142.

Structured Analysis and Design Technique

Structured Analysis and Design Technique Structured analysis and design technique (SADT) is a systems engineering and software engineering methodology for describing systems as a hierarchy of functions. SADT is a structured analysis modelling language, which uses two types of diagrams ...

(SADT) is a software engineering methodology for describing systems as a hierarchy of functions, a

diagram A diagram is a symbolic representation of information using visualization techniques. Diagrams have been used since prehistoric times on walls of caves, but became more prevalent during the Enlightenment. Sometimes, the technique uses a three ...

matic notation for constructing a sketch for a software application. It offers building blocks to represent entities and activities, and a variety of arrows to relate boxes. These boxes and arrows have an associated informal

semantics Semantics (from grc, σημαντικός ''sēmantikós'', "significant") is the study of reference, meaning, or truth. The term can be used to refer to subfields of several distinct disciplines, including philosophy, linguistics and compu ...

John Mylopoulos John Mylopoulos (born 12 July 1943) is a Greek-Canadian computer scientist, Professor at the University of Toronto, Canada, and at the University of Trento, Italy. He is known for his work in the field of conceptual modeling, specifically the dev ...

(2004)
Conceptual Modelling III. Structured Analysis and Design Technique (SADT)
Retrieved 21 Sep 2008. SADT can be used as a functional analysis tool of a given process, using successive levels of details. The SADT method allows to define user needs for IT developments, which is used in industrial Information Systems, but also to explain and to present an activity’s manufacturing processes, procedures.
at Free-logistics.com. Retrieved 21 Sep 2008. The SADT supplies a specific functional view of any enterprise by describing the functions and their relationships in a company. These functions fulfill the objectives of a company, such as sales, order planning, product design, part manufacturing, and human resource management. The SADT can depict simple functional relationships and can reflect data and control flow relationships between different functions. The

IDEF0 IDEF0, a compound acronym ("Icam DEFinition for Function Modeling", where ICAM is an acronym for "Integrated Computer Aided Manufacturing"), is a function modeling methodology for describing manufacturing functions, which offers a functional model ...

formalism is based on SADT, developed by

Douglas T. Ross Douglas Taylor "Doug" Ross (21 December 1929 – 31 January 2007) was an American computer scientist pioneer, and chairman of SofTech, Inc. He is most famous for originating the term CAD for computer-aided design, and is considered to be the fat ...

in 1985.

IDEF0

is a function modeling methodology for describing

manufacturing Manufacturing is the creation or production of goods with the help of equipment, labor, machines, tools, and chemical or biological processing or formulation. It is the essence of secondary sector of the economy. The term may refer to a ...

functions, which offers a functional

modeling language A modeling language is any artificial language that can be used to express information or knowledge or systems in a structure that is defined by a consistent set of rules. The rules are used for interpretation of the meaning of components in the ...

for the analysis, development, re-engineering, and integration of

information system An information system (IS) is a formal, sociotechnical, organizational system designed to collect, process, store, and distribute information. From a sociotechnical perspective, information systems are composed by four components: task, people ...

s; business processes; or software engineering analysis.''Systems Engineering Fundamentals.''
Defense Acquisition University Press, 1999. It is part of the

IDEF IDEF, initially an abbreviation of ICAM Definition and renamed in 1999 as Integration Definition,IEEE Standard for Functional Modeling Language—Syntax and Semantics for IDEF0, Software Engineering Standards Committee of the IEEE Computer Soci ...

family of modeling languages in the field of

, and is built on the functional modeling language building SADT. The IDEF0 Functional Modeling method is designed to model the decisions, actions, and activities of an organization or system. It was derived from the established graphic modeling language

structured analysis and design technique Structured analysis and design technique (SADT) is a systems engineering and software engineering methodology for describing systems as a hierarchy of functions. SADT is a structured analysis modelling language, which uses two types of diagrams ...

(SADT) developed by

and

SofTech, Inc. SofTech, Inc. was a computer software company with offices in the United States and headquarters established in Lowell, Massachusetts. SofTech was a significant provider of software engineering tools and solutions in the 1970's as well as Product ...

In its original form, IDEF0 includes both a definition of a graphical modeling language ( syntax and

) and a description of a comprehensive methodology for developing models. The US Air Force commissioned the SADT developers to develop a function model method for analyzing and communicating the functional perspective of a system. IDEF0 should assist in organizing system analysis and promote effective communication between the analyst and the customer through simplified graphical devices. Varun Grover,

William J. Kettinger William J. (Bill) Kettinger (born ca. 1955) an American computer scientist and is the William S. Lee Distinguished Professor in Management Information Systems at Clemson University, known for his work in the field of business process modelling and ...

(2000). ''Process Think: Winning Perspectives for Business Change in the Information Age. p.168.

Axiomatic design

Axiomatic design Axiomatic design is a systems design methodology using matrix methods to systematically analyze the transformation of customer needs into functional requirements, design parameters, and process variables.*Suh (1990), ''The Principles of Design'', O ...

is a top down hierarchical functional decomposition process used as a solution synthesis framework for the analysis, development, re-engineering, and integration of products, information systems, business processes or software engineering solutions.Suh (1999). Axiomatic Design: Advances and Applications, Oxford University Press, 2001, Its structure is suited mathematically to analyze coupling between functions in order to optimize the architectural robustness of potential functional solution models.

Related types of models

In the field of systems and software engineering numerous specific function and functional models and close related models have been defined. Here only a few general types will be explained.

Business function model

A ''Business Function Model'' (BFM) is a general description or category of operations performed routinely to carry out an organization's mission. They "provide a conceptual structure for the identification of general

business function A business process, business method or business function is a collection of related, structured activities or tasks by people or equipment in which a specific sequence produces a service or product (serves a particular business goal) for a parti ...

s". It can show the critical

business process A business process, business method or business function is a collection of related, structured activities or tasks by people or equipment in which a specific sequence produces a service or product (serves a particular business goal) for a parti ...

es in the context of the business area functions. The processes in the business function model must be consistent with the processes in the value chain models. Processes are a group of related business activities performed to produce an end product or to provide a service. Unlike business functions that are performed on a continual basis, processes are characterized by the fact that they have a specific beginning and an end point marked by the delivery of a desired output. The figure on the right depicts the relationship between the business processes, business functions, and the business area’s business reference model.

Business Process Model and Notation

Business Process Model and Notation Business Process Model and Notation (BPMN) is a graphical representation for specifying business processes in a business process model. Originally developed by the Business Process Management Initiative (BPMI), BPMN has been maintained by the ...

(BPMN) is a

graphical representation Graphic communication as the name suggests is communication using graphic elements. These elements include symbols such as glyphs and icons, images such as drawings and photographs, and can include the passive contributions of substrate, colour an ...

for specifying

es in a

workflow A workflow consists of an orchestrated and repeatable pattern of activity, enabled by the systematic organization of resources into processes that transform materials, provide services, or process information. It can be depicted as a sequence ...

. BPMN was developed by

Business Process Management Initiative The Object Management Group (OMG) is a computer industry standards consortium. OMG Task Forces develop enterprise integration standards for a range of technologies. Business activities The goal of the OMG was a common portable and interopera ...

(BPMI), and is currently maintained by the

Object Management Group The Object Management Group (OMG) is a computer industry standards consortium. OMG Task Forces develop enterprise integration standards for a range of technologies. Business activities The goal of the OMG was a common portable and interoperab ...

since the two organizations merged in 2005. The current version of BPMN is 2.0. The Business Process Model and Notation (BPMN) specification provides a graphical notation for specifying

es in a

Business Process Diagram Business is the practice of making one's living or making money by producing or buying and selling products (such as goods and services). It is also "any activity or enterprise entered into for profit." Having a business name does not separate ...

(BPD). The objective of BPMN is to support business process management for both technical users and business users by providing a notation that is intuitive to business users yet able to represent complex process semantics. The BPMN specification also provides a mapping between the graphics of the notation to the underlying constructs of execution languages, particularly

BPEL4WS The Web Services Business Process Execution Language (WS-BPEL), commonly known as BPEL (Business Process Execution Language), is an OASIS standard executable language for specifying actions within business processes with web services. Process ...

Business reference model

Business reference model Business reference model (BRM) is a reference model, concentrating on the functional and organizational aspects of the core business of an enterprise, service organization or government agency. In enterprise engineering a business reference model ...

is a reference model, concentrating on the functional and organizational aspects of the

core business The core business of an organization is an idealized construct intended to express that organization's "main" or "essential" activity. Core business process means that a business's success depends not only on how well each department performs its ...

of an

service organization A service club or service organization is a voluntary nonprofit organization where members meet regularly to perform charitable works either by direct hands-on efforts or by raising money for other organizations. A service club is defined firstl ...

government agency A government or state agency, sometimes an appointed commission, is a permanent or semi-permanent organization in the machinery of government that is responsible for the oversight and administration of specific functions, such as an administrati ...

. In enterprise engineering a business reference model is part of an

Enterprise Architecture Framework An enterprise architecture framework (EA framework) defines how to create and use an enterprise architecture. An architecture framework provides principles and practices for creating and using the architecture description of a system. It struc ...

or ''Architecture Framework'', which defines how to organize the structure and views associated with an Enterprise Architecture. A reference model in general is a model of something that embodies the basic goal or idea of something and can then be looked at as a reference for various purposes. A business reference model is a means to describe the

business operations Business operations is the ''harvesting'' of value from assets owned by a business. Assets can be either '' physical'' or '' intangible''. An example of value derived from a physical asset, like a building, is rent. An example of value derived fr ...

of an organization, independent of the

organizational structure An organizational structure defines how activities such as task allocation, coordination, and supervision are directed toward the achievement of organizational aims. Organizational structure affects organizational action and provides the founda ...

that perform them. Other types of business reference model can also depict the relationship between the

es, business functions, and the

business area A central business district (CBD) is the commercial and business centre of a city. It contains commercial space and offices, and in larger cities will often be described as a financial district. Geographically, it often coincides with the "city ...

’s business reference model. These reference model can be constructed in layers, and offer a foundation for the analysis of service components, technology, data, and performance.

Operator function model

The ''Operator Function Model'' (OFM) is proposed as an alternative to traditional

task analysis Task analysis is the analysis of how a task is accomplished, including a detailed description of both manual and mental activities, task and element durations, task frequency, task allocation, task complexity, environmental conditions, necessary cl ...

techniques used by

human factors Human factors and ergonomics (commonly referred to as human factors) is the application of psychological and physiological principles to the engineering and design of products, processes, and systems. Four primary goals of human factors learnin ...

engineers. An operator function model attempts to represent in mathematical form how an operator might decompose a complex system into simpler parts and coordinate control actions and system configurations so that acceptable overall system performance is achieved. The model represents basic issues of knowledge representation, information flow, and decision making in complex systems. Miller (1985) suggests that the network structure can be thought of as a possible representation of an operator's internal model of the system plus a control structure which specifies how the model is used to solve the decision problems that comprise operator control functions.Operator Function Model (OFM)
. Accessed 27 Nov 2008.

References

{{DEFAULTSORT:Function Model Software architecture Systems analysis Systems engineering Software design Modeling languages