Clapp, G., Sworder, D. “Command, Control and Communications (C 3 )” The Electrical Engineering Handbook Ed. Richard C. Dorf Boca Raton: CRC Press LLC, 2000 103 Command, Control, and Communications (C 3 ) 103.1 Scope 103.2 Background 103.3 The Technologies of C 3 103.4 The Dynamics of Encounters 103.5 The Role of the Human Decisionmaker in C 3 103.6 Summary 103.1 Scope The focus of this chapter is not a detailed profile of a current or planned military C 3 system but it is rather on the issues and the technologies of the C 3 mission. Evolving technology, an evolving world order, and constant programmatic reorderings render such express descriptions to become rapidly outdated. Thus block diagrams of specific military systems (and listings of their acronyms) are de-emphasized. Of paramount interest is not electronics technology in isolation, but rather technology integrated into systems and analysis of these systems operating under complex real world environments that include technologically capable adversaries. The human commander or decisionmaker, as the principal action element in a C 3 system, is included explicitly in the system analysis. 103.2 Background Electronics technology is nowhere more intensively and broadly applied than in military systems. Military systems are effective only through their command and control (C 2 ) and this is recognized by the fact that C 3 is a critical discipline within the military. Frequently systems will be denoted C 2 I or C 3 I rather than command and control. This adds to C 2 the essential area of intelligence and intelligence products derived from surveillance systems. All variants of these acronyms are to be considered equal, whether or not communications, intelligence, or surveillance have been left implicit or made explicit. Likewise the superscript notation is considered optional and interchangeable. The formal discipline of C3 within the military has not been matched by focused technical journals or university curricula due to its highly multidisciplinary nature. Two definitions from a Joint Chiefs of Staff (JCS) publication [JCS, Pub. 1] capture the breadth of C2. This reference defines command and control as “The exercise of authority and direction by a properly designated commander over assigned forces in the accomplishment of his mission. Command and control functions are performed through an arrangement of personnel, equipment, communications, facilities, and procedures which are employed by a commander in planning, directing, coordinating and controlling forces and operations in the accomplishment of his mission.” C2 systems are defined, with almost equal breadth, as “An integrated system comprised of doctrine, proce- dures, organizational structure, personnel, equipment, facilities, and communications which provides author- ities at all levels with timely and adequate data to plan, direct and control their operations.” G. Clapp Naval Command, Control and Ocean Surveillance Center D. Sworder University of California, San Diego ? 2000 by CRC Press LLC A LOOK TOWARD FUTURE FLIGHT n March 19, 1996, NASA and McDonnell Douglas Corporation unveiled to the public a new subsonic flight vehicle designated X-36, a remotely piloted tailless research aircraft. The X-36 is designed to demonstrate the feasibility of future tailless military fighters that can achieveO ? 2000 by CRC Press LLC Though general, two points emerge from these definitions: (1) C 3 is multidisciplinary and (2) C 3 is a process which, to this point, includes only implicit roles for electronics technology. One military service, however, often refers to C 4 and C 4 I or has even used C 4 I 2 where the final C and second I refer to computers and interoperability, respectively, as acknowledgment of the increasing reliance on technology. A C3 system can be visualized as shown in Fig. 103.1. Within the constraints imposed by organization, doctrine, and the skills of the personnel of the military unit, the commander plans and controls his forces. At a basic level, command and control is a resource allocation problem, which often must be solved under much tighter time horizons and subject to greater uncertainty levels than exist in civil applications. agility levels superior to those of today’s aircraft. In the absence of a tail, control of the X-36 is accomplished by a combination of thrust vectoring and innovative aerodynamic control features. Tailless fighter configurations offer reduced weight, increased range, and improvement in survivability. The X-36 is “flown” by a pilot located in a van at the flight test facility; a camera in the XX-36 cockpit relays instrument readings and displays to a console in the van. With a wing span of only 10.4 feet and a gross weight under 1,300 pounds, the X-36 is powered by a single turbofan originally designed as a cruise missile power plant. The X-36 program is intended to establish confidence to incorporate these technologies in future piloted vehicles. This project exemplifies one aspect of a NASA aeronautical research and technology program that seeks to improve the performance, efficiency, and environmental characteristics of all types of planes and, additionally, addresses such infrastructure factors as air traffic control, navigation, and communications. (Courtesy of National Aeronautics and Space Administration.) Designed jointly by NASA and McDonnell Douglas Corporation, the X-36 is a subscale, remotely piloted tailless vehicle for demonstrating technologies that could lead to lighter, longer-ranging, more survivable, more agile military fighter aircraft. (Photo courtesy of National Aeronautics and Space Administration.) The four basic components display overlapped regions to indicate their inseparability. A portion of each category can be designed in isolation; a new antenna or a new radio with decreased size, weight, or power consumption has minimal impact on the other components. However, insertion of a broad new technology (e.g., a radio relay combined with a remotely piloted vehicle (RPV) or the networking of radios) has wide reaching consequences and it may take years to fully integrate into doctrine, training, and organization. The conjunction of the four areas, when specified with some detail, represents or contains an architecture. If the assets, the doctrine, and so on are limited to just one military function, then the aggregation is referred to as a mission architecture. Figure 103.2 depicts two approaches to achieving C3 architectures. The first [Fig. 103.2(a)] is essentially an aggregation and combination of existing assets and is referred to as a “bottom- up” architecture. The “top-down” version of architecture development [Fig. 103.2(b)] begins with earlier and high order perspective (and higher order oversight). Interfaces and interface standards become more important in top-down architectures; instead of numerous custom and unique interfaces, a minimal set of interface standards is desired. When new or updated equipment is designed or acquired it can be integrated without new interface developments, a key property of an “open system” architecture. A developing architecture of this type is entitled, at the Joint Chiefs of Staff level, “C4I for the Warrior.” Service-specific top-down architec- tures are Copernicus (Navy), AirLand 2000 (Army), MTACCS (Marine Corps Tactical Command and Control System) and a yet unnamed Air Force architecture. Each of these are to be considered as evolving architectures and all reflect the impact and importance of scenarios with highly mobile nodes. The open system or top-down approach promotes interoperability between the developments of each service. Capital investment constraints limit strict adherence to either architectural approach. MTACCS is a meta- system of seven independently developed systems and is best described as a hybrid architecture. Most commu- nication systems within any of the above architectures existed prior to an architecture and thus have a hybrid nature. Doctrine is a formalized description of military mission definitions and often includes the procedures to accomplish those missions. Doctrine will also often specify the organizational structure appropriate to the specific missions. Some military establishments adhere to strong doctrinal orientation, even down to strict dictation of technology developments. Other establishments treat doctrine as a loose guideline that can be liberally modified. One foreign military analyst observed that U.S. commanders did not seem to read their own doctrinal publications, and even if they did, would not feel compelled to follow them. A flexible military organization with flexible doctrine, however, can be constrained by inflexible hardware and software. Thus an emerging C3 emphasis is a technical focus on modular equipments, standard interfaces between equipments, “open system” architectures, and (software) programmable equipments. The best way to understand military C3 is to view it as a set of adaptive control loops. The basic variable is information and most of the effort in C3 synthesis is devoted to information handling and management. The resource allocation problem with feedback found in C3 has obvious similarities to those found in corporate operations and public safety service operations. Each is characterized by multiple priorities, limited resources, timelines, and deadlines for performance. Measures of the consequences of a given action tend to be obscured both by its antecedent actions and by changing external environments. The external environment contains both continuous events (i.e., tracking of targets) and discontinuous events (i.e., an equipment failure or the onset of communications jamming). FIGURE 103.1 Components of C 3 . ? 2000 by CRC Press LLC Command and control systems are examples of perhaps the most complex adaptive systems. In its static state, C3 assets are aggregates of sensors, processors, databases, humans (with their attributes and organizations), computer hardware/software, mobile platforms, weapons, and communication equipments distributed over wide areas. In the dynamic state these assets must be mapped into capabilities in the presence of uncertain or unexpected threats, evolving missions, changing environments, mixed with unreliable communications and possible deception. All can be expected to occur over extended geographic regions and at high tempos. In short, C 3 maps assets into capabilities. The control processes require rapid and accurate decisionmaking; from this has come the need for heavy reliance on computer-based data systems and high-reliability communications. Despite the existence of fielded weapon systems capable of autonomous operation, the principal action element in the system is still human. C3 system complexity arises primarily from the magnitude and mobility of the forces involved; forces that can be composed of up to thousands of mobile platforms and hundreds of thousands of personnel. To this is added the large amount of uncertainty present; uncertainty borne of the adversary, of human attributes, dynamics, hostile environments, and communications. Hundreds of radio frequency channels may be in simultaneous use supporting command, surveillance, intelligence, personnel, and logistics functions. 103.3 The Technologies of C 3 The general scenario outlined in the previous sections is no longer accommodated by last generation technology of grease pencils, maps, and visual signaling. Technology covered in nearly every other chapter of this handbook is rapidly being incorporated into military C3 systems. Defense departments world wide continue to support technology developments from sub-micron microprocessing devices to global information systems. Technologies with recent major impact on C3 are a.Digital communications/data links/networking. The newer and critical role of digital (computer-com- puter) communications initially became possible through satellite communication systems. Tactical data links (short-range digital communications) have been enhanced by error control techniques such as coding, automatic repeat requests, and spread spectrum radios. Networking, a well-established commercial technique, is being developed for tactical applications. Networking offers survivability through alternate FIGURE 103.2 Architectural processes. ? 2000 by CRC Press LLC routing, more efficient (shared) use of channel capacity, and interoperability between interconnected users. Commercial Integrated Services Digital Networks (ISDN) and Asynchronus Transfer Mode (ATM) technology is appearing in both global and nodal military applications. Traditional voice communica- tions remain important; Department of Defense directives require all voice circuits to be secure or encrypted. Digitized voice techniques offer advantage in digital encryption and compression. b.Space surveillance, terrestrial surveillance, data fusion. The quantity and quality of surveillance systems continues rapid growth utilizing sensors from ground-based, airborne, and space-based vantages. Remote sensing requirements continue to expand the need for real time digital data communications. Unmanned Airborne Vehicles (UAV) and Unmanned Underwater Vehicles (UUV) platform developments continue as a response to a broad range of C3I needs. Two classes of surveillance are active surveillance systems (radar, sonar, and optical) and passive systems (electronic surveillance measuring (ESM), acoustic, infra- red and visual imagery). Passive techniques are preferred as they do not leave a signature that can be exploited by adversaries. A plethora of new sensor systems challenges the currently available communi- cations, processors, and processing systems. Particularly challenging is both the fusion of the outputs of multiple similar sensors and also of dissimilar sensor systems. Fusion protocols and tracking algorithms, software intensive, claim an increasing fraction of available resources. With multiple new sensor systems, a technology challenge is the processing, correlation, and fusing of surveillance data into intelligence products and their distribution in a timely and usable form. c.Computer-based data and information systems. From the communications and surveillance capabilities above, the objective has become formation of a consistent tactical picture throughout the operations theatre. Rapidly evolving processing technology allows vast amounts of data handling and management with corresponding shortening of control decisionmaking times. The ability to match computer pro- cessing capability with high data rate, reliable, and survivable computer-grade communications on a global basis to small mobile platforms is an ongoing challenge. Military information systems, in order to retain trusted functioning, require procedures for input data that may have been delayed, omitted, partial, inaccurate, or irrelevant (DOPII). Expanding amounts of software-based systems are needed as a response to increased tempo, data volume, and quality while reducting staff and manpower functions. d.Architectures and architectural thinking. C3 assets, especially communications, are evolving as assets to be shared, controlled, and rapidly reallocated rather than be dedicated to a specific user. Joint and combined operations, requiring improved interoperability, are becoming common as operations become more regionalized. Two functions of focus, Battle Damage Assessment (BDA) and Indicators and Warn- ings (I&W), are best implemented when surveillance, communications, and intelligence are architectur- ally integrated. Integrated systems are also best for timely response to deception and false alarms. A current Navy direction is not to inundate the afloat commander with volumes of unsolicited data but rather have him request what is needed. This style, called information pull, represents a significant change from traditional information push. The impact on supporting communications is to give it a more “bursty” character, driven by external events. e.Digital signal processing, programmable systems. Single-function C3 hardware is evolving to multifunc- tion capability. Each node or platform will emerge with new capabilities that permits rapid and flexible reallocation. Current generation tactical military aircraft, as delivered, have virtually no additional space or weight allowance for new equipments. A desire is to evolve from costly retrofitting to a state of software insertion and integration. Traditional single-band radio systems will be replaced with programmable multiband, multiwaveform systems. Near real-time management and control of highly flexible, pro- grammable systems will become a growing research and development thrust. Next generation cellular technology involving hybrids of frequency hopping, direct sequence spread, and time division spread spectrum techniques invokes new digital signal processing efforts. Also receiving development is Direct Satellite Broadcast (DSB) to tactical military units. f.Interoperability and standards. C3I systems, with many dispersed nodes, rely heavily on computer- computer communications. Standards are being promoted by industry and government to simplify the development, acquisition, and insertion of new technology as well as to promote interoperability between ? 2000 by CRC Press LLC independently developed systems. Significantly the Department of Defense has edicted that commercial standards for electronics and telecommunications are to be utilized in preference to military standards in order to promote more rapid and lower cost acquisition of state-of-the-art technology. Two additional motivations for new standards are increased traffic requirements and increased system complexity. C3 applications and users have found significant benefit in increasing communication with programmati- cally unrelated data sources such as databases and sensors. There is an increase in internal communica- tions as well. Also systems have become more complex, forcing programs to develop modularized architectures. Software is replacing hardware as the most complicated component of communications and C2 systems to design, build, and maintain. Modularized architectures are required to simplify development and enable insertion of new technologies. The primary computer-to-computer communications architecture has been the Open Systems Inter- connection (OSI) Reference Model. The OSI Reference Model has been successful as a layered architecture with well-defined interfaces and specified division of functions. The Department of Defense has com- mitted to adopting an enhanced version of the OSI protocols, called the Government OSI Profile (GOSIP). OSI/GOSIP integration into C3 systems is lagging because of delays in accredited vendor implementations and the cost of upgrading the existing communications infrastructure. NATO is also adopting standards for their joint procurement policies; to a significant degree they overlap commercial standards. OSI brings to C3 a set of application services that had not been previously available. For example, the OSI electronic mail standards (usually called X.400) provide message forwarding, distribution list cre- ation and distribution, and obsolete message extraction among other services to users. In addition to the security protocols contained in the lower layers of the OSI stack, X.400 has its own security services such as message origin authentication, message flow confidentiality, message content integrity, and nonrepudiation of delivery, services that are highly desirable in C3 environments. OSI also has enhanced file transfer and management capabilities, systems management, directory, and transaction processing, among other application functions, all providing enhanced capability to C3 users. g. Precision timing and position location (GPS). Navigation/position location historically is important and becomes more so in high dynamic maneuver warfare. With the introduction of the Global Positioning System (GPS), 3-dimensional positioning is available to the smallest of high-mobility nodes. Even with a less than complete satellite constellation, position accuracies can become less than 100 m. h. Displays and workstations. High-resolution displays combined with programmable workstations and software lead to flexible node functions and consequently to flexible architectures. A C3 workstation could, in principle, support any of a number of C3I functions; a relocation of operators may be the only requirement to physically relocate a command node. Numerous decision aids are now being included within workstations and with their more comprehensive capability are now often described as decision support systems (DSS). Man-machine interface (MMI), as a result, grows in importance. i. Software techniques. With the growing computational power and memory capability of microprocessor systems, C3 system performance will increasingly be determined by software performance. The cost and complexity of software appears to expand in proportion to host computer capability and is more frequently becoming a system limiting factor. ADA is dictated to be the common programming language of the Defense Department; however, exceptions can be approved. Verification and validation (V&V) of generated software and software maintainence have grown to necessitate organizational changes within the military. Software standards have also increased in importance in new C3 systems. POSIX standards (published as IEEE 1003) govern the software interfaces to operating system services in various com- puting platforms [NIST, 1990]. As such, they allow application programs written according to the standards to be reused. POSIX standardizes interfaces to security, networking, and diverse system services, including file management, memory and process management, and system administration services. POSIX.5 provides bindings for the ADA programming language. j. Simulation and modeling. Both techniques are employed with the objective of designing or analyzing the performance of a C3I system. With the advent of faster computation, complex scenarios can be “gamed” in near real time, and modeling will then be within the decision aid realm. ? 2000 by CRC Press LLC 103.4 The Dynamics of Encounters Within dynamic systems, and the C3 systems that support them, it is important to identify and clarify time scales involved. Military engagements range from sub-second events such as local missile point defense to the long-term development and implementation of global strategy. Each involves basic aspects of decision and control theory: objectives, observations, and feedback and control. In the military environment, the observation aspect is especially complex, requiring the placement, collection, transmission, and aggregation of data from numerous dispersed sources. Control and decision techniques derived for one echelon level may be inappro- priate for others, primarily due to the time available for the assessment and feedback process. Often, the impact of a decision will not be measurable before yet another control decision is required. Thus, the relative roles of automation and humans will be different at different levels. The human may have to project a decisionmaking consequence long before the system hardware/software can obtain measures of it. As an example of encounter space-time domains, surface Navy echelon levels have order-of-magnitude scales as shown: At the platform level, the time scale range reflects engagement times which may include limited or local amounts of tracking. At the Battle Group level, the time scale corresponds to tasks such as maneuver, coordinated engagement, and track management. Any of the organizational levels may additionally have planning functions that precede the operational time scales by up to months or years. The planning side includes events such as logistics, maintainence, training, and exercises, all of which contribute toward becoming a more capable combatant. Figure 103.3 portrays the planning and the operational or execution phases as well as portraying the adaptive control loop approach to C3. The lighter shaded feedback path is employed when it is required to compare status with the current plan. It is also available for adjustment when plans or objectives are modified. The execution phases are represented by the Stimulus-Hypothesis-Options-Response (SHOR) Paradigm suggested by Wohl [1981]. The control the- oretic implications are apparent in the figure; the Stimulus-Hypothesis is a representation of situation assess- ment with its implicit uncertainty. Quickness and accuracy with which a military command organization can transverse the execution loop is a general measure of performance (MOP). Qualitatively it is generally accepted that the side with the best ability to transverse the SHOR execution loop will have a significant military advantage. In this light, attributes of the execution loop become a measure of effectiveness (MOE) of the C3 system in terms of operational outcomes. Rules of Engagement (ROE) impact tempo by reducing uncertainty or options available to the decisionmaker. Some scenarios develop with such quickness that the C3 system must react nearly reflexively (e.g., without consideration of possible options). One class of rules is made known to all the participants; if a particular manuever is observed, then a specified response will result. The SHOR paradigm illustrates why counter-communications and counter-command and control are increasingly important operational and technical areas. Counter-C3 need only delay the process rather than disrupt or destroy it in order to be an effective technique. The Navy, for example, is now incorporating electronic warfare (EW) as a warfare area on equal status to the traditional anti-submarine (ASW), anti-aircraft warfare (AAW), and anti-surface warfare (ASUW) areas. Control of the electromagnetic spectrum is becoming as critical as the control of the physical battlefield. Electronic counter-measures (ECM) such as jamming and deception are technical options available to the commander. Either adversary may elect to respond to the ECM threat by a series of electronic counter-counter measure (ECCM) techniques. Anti-jam (AJ) communications can employ a variety of techniques such as spread spectrum, power control, adaptive coding and feedback, multiple routes, and adaptive antenna arrays. A signal Organization Level Time Scale of Interest Geographic Extent (km) Platform seconds-minutes 10’s Battle Group minutes-hours 100’s Fleet hours-days 1000’s Theater days-weeks 1000’s + Service/National weeks-years Global ? 2000 by CRC Press LLC may also be protected by making it difficult to intercept; some low probability of intercept (LPI) methods are again spread spectrum, directive antennas, power control, EM propagation strategies, and message brevity. The SHOR paradigm has important advantages. First, it is generally applicable to all military echelon levels. Second, it represents a control process with its explicit dynamics rather than a relational or physical intercon- nection of system components. Finally, it puts focus on the roles of controlling and decisionmaking without a pre-bias on whether that function should be performed by humans or computers. The remaining challenge is to be able to describe both human and computer performance with a common type of representational framework. 103.5 The Role of the Human Decisionmaker in C 3 Designers of C3 systems often fail to acknowledge the fact that the “central, essential ingredients in any command and control system are not the things which they plan and design; rather they are the commanders and decisionmakers themselves” [Wohl, 1981]. Despite its centrality, designation of human roles is seemingly arbitrary and often controversial. In most system studies, the human decisionmaker is not thought of as an integral part of the system, but is instead given an external position as a “user” of data or an “input” to the rest of the system. Without a means of integrating the behavior of interrelated decisionmakers into a comprehensive description of system response, the proper hominal role is difficult to determine. To justify and support human action, a clear understanding of the benefits and limitations of human intervention is required. The complexity and unpredictability of a C3 environment prompt the inclusion of hominal blocks. The ability to respond to changing operational conditions requires “intelligence,” and in a C3 system this intelligence is distributed between people and algorithms. The human has a marvelous capacity for coping with vague and confusing data, making sense out of information so fragmentary that it would paralyze a computer. A computer information processing algorithm has, in turn, an unexcelled capability to process and display data at a rate that would bewilder a person. Proper marriage of humans and computers yields a robust system, quick to adapt to changes and capable of handling high data rates. For example, for the various subtasks found in the network management component of a C3 system, the relative roles of people and algorithms might be that shown in Fig. 103.4. With the advent of open system architectures, network management appears as a crucial resource allocation function. High speeds and large databases are best left within the domain of the computer, while those nodes demanding insight appropriately have a corporeal flavor. A comprehensive C2 model is created by bringing together models of subsidiary elements. The form of these submodels should be as compliant as possible within constraints imposed by tractability. In any event, the model should display: FIGURE 103.3 The planning and execution phases of operations. ? 2000 by CRC Press LLC 1. An analytical structure permitting the evaluation of influence functions 2. Explicit communication dependence 3. Amenability to aggregation and disaggregation Each of these desiderata arises in studies within the field of System Science, and this discipline would appear to provide the natural formalism for quantitative investigations of command and control systems. Athans articulates this view by observing that C3 systems “are characterized by a high degree of complexity, a generic distribution of the decision-making process among several decision making ‘agents,’ the need for reliable operation in the presence of multiple failures, and the inevitable interaction of humans with computer-based decision support systems and decision aids” [Athans, 1987]. It needs to be emphasized, however, that a C2 system differs from those commonly encountered in system theory in at least three primary ways: 1. Because command and control is at its essence a human decisionmaking activity, it is not sufficient to model only the sensors, computers, displays, etc. The hominal dynamics must be integrated with those of the electromechanical elements. 2. Any effective C3 system must have the capacity to evolve over time. Such systems are frequently estab- lished with a limited set of elements. Either for a specific operation or during their lifetime a subset of these elements will be modified or replaced, and their roles expanded or constricted as changing demands are placed upon the system. Hence, the system description must be more flexible than those in common use. 3. In contrast to conventional system design problems, there is no single nominal operating condition about which the system is maintained. Indeed, the critical attribute of a C3 system is its ability to respond to major changes in condition or state. In two Middle East naval events (USS Stark, Vincennes) the missile defense systems were set for a state that had just immediately changed. Furthermore, the system is often used in environments quite different from those envisioned in its design. Hence, the uncertain circum- stances within which the decisionmakers must accomplish their tasks must be properly reflected in any system architecture. A commander brings special skills to such a system, but some of them are difficult to quantify. For example, people have singular competence in: 1. Decisionmaking in semantically rich problem domains 2. Analogical reasoning and problem structuring 3. Information processing and application of heuristics To properly identify a specific function for a human decisionmaker, the advantage accruing to his inclusion must be shown. Quantitative models of human responses have been developed in various ways, from ad hoc to purely normative. In the most promising of these, the form of the response dynamics of an individual commander is determined from the solution to an optimization problem. The optimization problem is framed by supposing that the decisionmaker strives to act in the most effective way, but is constrained by both cognitive FIGURE 103.4 Control hierarchies. ? 2000 by CRC Press LLC limitations and temporal pressures. When the decisionmaker’s milieu and motivation are expressed in an analytical framework containing both the exogenous influences of the conflict and the endogenous predispo- sitions generated by training and personal inclination, the input-output relation for the commander is, in principle, expressible as a set of differential equations with logical branching. This fundamental modeling philosophy has been used successfully by several investigators. Wohl developed the SHOR model of decisionmaker action using the ideas from modern systems theory. The SHOR, in con- junction with planning models (see Fig. 103.3) can be phrased in analytical terms compatible with those of the electromechanical subsystems. With their common form, all of the submodels can be combined to create a comprehensive system description, integrating people with hardware and software algorithms. This model is useful in system architecture studies because it is applicable to all military echelon levels; it represents the fast dynamics of the system explicitly rather than by implicit relational blocks or physical interconnection of subsystem elements, and there is flexibility to allow whether a function is best performed by a human or by an algorithm. A decisionmaker views a dynamic encounter as a temporally varying, geographically dispersed system subject to unpredictable events, both continuous and discrete. Because critical command decisions have an extended period of influence, the actions taken at different time scales cannot be isolated from each other. This issue of scale interaction comes to the fore particularly when hominal modeling is considered. In contrast to inanimate objects which usually have a single, natural time scale, the demands on a commander transcend the time scale divisions. A trained decisionmaker exhibits a wide spectrum of behaviors as both his tasks and operating environments change; the commander is the truly adaptive block in a command and control architecture. Athans referred to C3 systems as “event driven” because major changes in an engagement occur at isolated times and modulate the more frequent local irregularities [Athans, 1987]. He suggested that the proper model would be a hybrid in which “the state variables are both continuous and discrete.” In this metapartitioning of the comprehensive state space, the discrete states represent global (or macro) occurrences that modulate the local (or micro) aspects. This decomposition is useful in formulating the human response model because people react differently in different time scales. The reaction to local phenomena has a reflexive quality. It is in this reaction to the infrequent, but pivotal, macroevents that the idiosyncracies thought to be particularly human are manifest. To capture hominal behavior analytically, a framework delineating the intrinsic features of a C3 environment is required. At the macrolevel, the important attributes of a command and control environment are tempo, uncertainty, and complexity. The mission directed decisionmaker model (MDDM) described in Clapp and Sworder [1992] decomposes the C2 model in the hybrid form suggested by Athans. One block in the MDDM, the stimulus-hypothesis evaluation model (SHEM), quantifies relevant features of an engagement while repre- senting the observation and situation assessment tendencies of the decisionmaker in terms of a few natural parameters. Because of its simple structure, the SHEM lends itself to the analysis of systems containing human decisionmakers. To be more specific, the C2 environmental model must be flexible enough to portray the sudden, large-scale variations in circumstances which occur in operations. It is advantageous to phrase the model in such a way as to make explicit its dependence on events of macroscopic scale as well as the decisionmaker’s response. The engagement model used in the MDDM has the form: (d/dt)x p = f (x p ,u p ,r t ) + g(x p ,u p ,r t )w t where x p is the “global” system state vector representing the external environment to which the decisionmaker seeks to respond. The decisionmaker’s action variable is u p . The process {w t } represents only one portion of the primitive randomness in the encounter—that associated with high-frequency uncertainty and various local disturbances. The supplementary process, {r t }, indicates the mode of evolution of the encounter. Transitions in {r t } thus signify extensive events. These macro-events tend to have more temporal structure than that displayed by {w t }, but the times of occurrence are typically unpredictable. Different values of r t (sometimes called supervariables) are identified with different hypotheses delineating the macrostatus of the encounter. It is usually assumed that the number of modal hypotheses is finite. ? 2000 by CRC Press LLC Even with the aggregation implicit in the engagement model, the encounter dynamics are complex and nonlinear. A decisionmaker mentally converts the engagement dynamics into a hybrid equation with separate descriptions of local and global aspects. The input-output dynamics of the commander are expressed as an ordinary differential equation with updates at observation times. In Sworder et al. [1992], the ability of the SHEM to predict the response of a trained decisionmaker was investigated. An experiment measuring the proficiency of trained air-defense officers in differentiating hostile from friendly targets confirmed the utility of the SHEM. 103.6 Summary C3I systems, commanders/decisionmakers, and decision aids all have a common performance objective. They must contribute to accurate and timely situation assessments and responses in scenarios that have a wide range of tempos, noise, clutter, uncertainty, and complexity. The C3 system necessarily has the ability to rapidly acquire, process, and transfer large volumes of data over extended regions. Trained, experienced human decisionmakers excel at assessing complex patterns in highly cluttered environments and determining appropriate responses. Decision aids perform as a “smart” interface between these two dissimilar players. Electronics technology provides the means for designing increasingly capable C3 systems and is at its most effective when the system architecture allows flexible and dynamic interoperation of the various hardware “devices” with their trained and motivated decisionmakers. Defining Terms Command, control, communications (C 3 ): The process of mapping assets (resources available to the military commander) into capabilities. This control process is impacted by tempo, noise/clutter, and scenario complexity. Decisionmaking: A commander’s or operator’s action that changes the status of his information or other assets under his control. Doctrine: A formalized description of military mission definitions to include the procedures to accomplish those missions. Doctrine will also often specify the organizational structure appropriate to the specific mission. Electronic warfare: Contention for the control of the electromagnetic (EM) spectrum, to allow active and passive EM sensing and communications while denying the same ability to adversaries. Includes deceptive EM techniques. Environment: A set of objects outside the system, a change in whose attributes affects, and is affected by, the behavior of the system. Information warfare: The protection, manipulation, degradation, and denial of information to include the traditional electronic warfare. Intelligence: The aggregated and processed information about the environment, including potential adver- saries, available to commanders and their staff. Open system architecture: A layered architectural design that allows subsystems and/or components to be readily replaced or modified; it is achieved by adherence to standardized interfaces between layers. Programmable radio system: Radios based on digital waveform synthesis and digital signal processing to allow simultaneous multiband, multiwaveform performance. System: A set of objects with relations between them and their attributes or properties. It is embedded in an environment containing other interrelated objects. Related Topics 70.1 Coding ? 102.2 Communications Satellite Systems: Applications ? 2000 by CRC Press LLC References M. Athans, “Command and control (C2) theory: A challenge to control science,” IEEE Trans. on Automatic Control, vol. AC-32, pp. 286–293, April 1987. G.A. Clapp and D.D. Sworder, “Command, control and communications: The human role in military C3 systems,” in Control and Dynamic Systems, Advances in Theory and Applications, vol. 52, New York: Academic Press, 1992, pp. 513–541. S. Johnson and M. Libicki, Eds., Dominent Battlespace Knowledge: The Winning Edge, Washington, D.C.: National Defense University Press, U.S. Government Printing Office, 1995. Joint Chiefs of Staff (JCS), Publication 1, “Definitions,” undated. M.C. Libicki, What is Information Warfare?, Washington, D.C.: National Defense University Press, 1995. National Institute of Standards and Technology [NIST], FIPS 151-1, POSIX: Portable Operating System Inter- face for Computer Environments (IEEE 1003.1–1988) March 1990. D.D. Sworder, G.A. Clapp, and R. Vojak, “A Dynamic Input-Output Model of the Decisionmaking Process,” Proceedings of the 1992 Symposium on Command and Control Research, Monterey, Calif., June 1992. J.W. Wohl, “Force management requirements for air force tactical command and control,” IEEE Trans. on Systems, Man and Cybernetics, vol. SMC-11, pp. 618–639, Sept. 1981. Further Information W. Stallings, Handbook of Computer-Communications Standards, vol. 1, The Open Systems Interconnections (OSI) and OSI-Related Standards, New York: Macmillan, 1987. W. Stallings, Handbook of Computer-Communications Standards, vol. 3, Department of Defense (DOD) Protocol Standards, New York: Macmillan, 1988. Information Technology for Command and Control, S. Andriole and S. Halpern, Eds., IEEE Press, New York, 1991. SIGNAL, a monthly (trade) magazine published by the Armed Forces Communications-Electronics Association (AFCEA), Annandale, Va. Contains numerous brief articles on current C3I topics of interest. T.P. Coakley, Command and Control for War and Peace, National Defense University, U.S. Government Printing Office, Washington, D.C., 1992. A.D. Hall, Metasystems Methodology, Oxford, England: Pergamon Press, 1989. ? 2000 by CRC Press LLC