ABSTRACT. A Headquarters (HQ) is a core capability used by a Commander to assist in the Command and Control (C2) an assigned Force. But how does a HQ know if it’s making progress in its development? How does it know if it is more effective? Typically, a HQ will train in peacetime to improve its performance, in order to be more capable when deployed on operations. A HQ with a limited capability may well perform adequately in one type of situation, but very much less well in one which is more complicated. For the same HQ to perform equally well in a variety of situations is a sign of both its adaptivity and maturity. There has been some work on assessing C2 effectiveness in military exercises and Experiments, but currently there is no acknowledged standard to determine whether beneficial change and improvement is taking place in a HQ. To address this shortfall this paper presents a Headquarters Maturity Model (HQMM) that is intended to provide a common framework for the development and maintenance of HQ competence and effectiveness.

ABSTRACT. In current and future operations, forces face strategies and tactics that are increasingly hybrid and networked in character: regular and irregular opposition intertwined in three different landscapes (physical, human/social and information) with multiple actors connected in a variety of networks. These networked opponents show remarkable elusiveness, resilience and effectiveness when facing military forces with a traditional hierarchical approach to command and control. We belief that hierarchical C2, even when applying Mission Command, is a major impediment to mission effectiveness against such networks. This implies that new forms of command and operations are needed to prevent becoming outdated, outpaced and outmaneuvered.

This paper introduces NetForce, a new concept that can replace traditional hierarchical C2. We define NetForce as the total collection of civilian and military capacities in a networked coalition interacting with each other and working towards achieving a common objective. NetForce is characterized by (near) autonomous functional civilian and military nodes that are self-synchronizing, aggregating and disaggregating in accordance with the demands of operational reality. In this paper we describe three appearances (archetypes) of a potential NetForce. Appearances vary from maximum self-synchronization to maximum orchestration and may have orchestrating elements to support the (self) synchronization of actions of military and civilian capacities.

ABSTRACT. In the new world of asymmetrical and other forms of warfare, adaptability and agility will be key features of military forces in meeting new operational requirements resulting from these forms of warfare. A joint-project arrangement has been established between Sweden, the Netherlands and Canada in order to study the concepts of adaptability and agility in military organizations. Canada’s research program addresses institutional leadership and its influence on organizational outcomes such as adaptability. The Dutch program focuses on strengthening both individual and organizational adaptability. The Swedish program is developing empirical research methods to assess adaptability and command and control (C2) agility by assessing the relationship between adaptability and agility on performance in the navy. The trilateral project arrangement enables collaboration in developing increased understanding of human and organizational adaptability and agility across multiple international military organizations. This paper presents a joint framework and initial findings from both the collaboration and the separate national efforts, including the balance between robustness and flexibility, organizational change, training, assessment, innovation, and maintenance of best practices.

ABSTRACT. Command and Control (C2) agility, as stated from the NATO SAS-085 asserts that there is no best approach to C2. We envision situations where adversarial entities are working to interfere with a composite C2 network and an underlying communications network. The interactions of these two networks are critical on the battlefield because C2 agility cannot exist without the ability to communicate between units. Based on previous work, we have designed a game theoretic approach geared towards finding stable states in the composite network graphs with the goal of maximizing performance of the organization. We select topologies in which to operate, and based on an attack strategy of the adversary, we maneuver and adapt the composite networks to ensure continuous flow of communication through the chain of command. We additionally show how proper embedding of the C2 network into the communications network can better prepare it against adversarial attacks. We posit that this approach can be applied to organizational structures with different multilayered approaches (i.e. logistics networks, socio-technical networks, cyber physical systems).

ABSTRACT. The “Thousand-Ship Navy” originally unveiled in 2005 by then-U.S. Chief of Naval Operations, Admiral Michael Mullen, is a concept that has gained traction over the years. Although the idea of international naval cooperation was rapidly embraced by the community of nations, the challenges of actually achieving coalition interoperability have been daunting.

No single navy is robust enough to enforce the rule of law in the global commons—or even respond well to a natural disaster. In order to build a successful Global Network of Navies (GNN), coalition partners need an international C2 system that will allow them to seamlessly and rapidly share information in order to generate an accurate Common Operating Picture (COP).

A variety of partners have a wide range of technological capabilities and different levels of funding to support such an undertaking. To address this challenge, Space and Naval Warfare Systems Command (SPAWAR) has developed web-based Service Oriented Architectures (SOAs) to deal with interoperability challenges. The challenge lies in connecting multiple SOAs to generate an accurate COP.

As the United States “Rebalances to the Asia-Pacific Region”—a maritime theater with many allies and partners having first-rate navies the United States needs to partner with—the imperative to work from the same COP and seamlessly exchange information has never been more important. Our paper will show why developing this international C2 system is crucial to United States security and prosperity, as well as how we are designing systems to help make the GNN a reality.

ABSTRACT. Coalition operations require multiple organizations with a variety of national, organizational, and professional cultures to work together. Cultural differences can be a source of conflict. In a coalition, such differences must be resolved by time-consuming negotiation, but there is little time for this during an operation. Instead, we argue that commanders would be better served by using simulation techniques before operations begin to choose an organizational design and C2 approach that minimizes intra-coalition cultural conflict.

The purpose of this paper is to propose a conceptual model for simulating multi-cultural coalitions using agent-based techniques, with agent behaviour being regulated by cultural norms. Following an introduction, related theory on organizational culture, norms, and agent-based simulation is summarized. The conceptual model is described, following which some experimentation using hand simulation is outlined. Previous research is reproduced and then extended to show that failure can occur from cultural differences. Finally, conclusions are drawn and further work is recommended.

ABSTRACT. Tactical battlespace information management is an ongoing challenge given the known constraints of operating in disconnected, intermittent and limited (DIL) network environments and the growing information requirements of soldiers at the tactical edge. This challenge becomes greater when operating in joint or C2 coalition environments and can seriously undermine the exercise of tactical C2 Agility and resilience. In order to address some of these challenges, we apply C2 Agility design principles outlined by SAS-085 to a multilayer network representation of a coalition tactical network environment based on a tactical level operational scenario. We present initial arguments for the potential benefits of using these approaches. Our measures of performance are informed by semantically aware metrics that aim to assess performance from a multilayer network perspective. We conclude by demonstrating that C2 Agility design principles can be used to inform the information management policies used to maneuver through the various configurations across which battlespace information management systems can operate.

ABSTRACT. The concept of command and control agility (C2 agility) has deeply impacted military operations, past and present. This paper will analyze the conduct of operations in two historical cases by using the concepts of command and control agility by Dr. David Alberts and the NATO System and Analysis Studies group 085.

This concept will be used to explain and measure the appropriateness of the command and control approach in the historical missions. In each case, three elements will be measured. These are allocation of decision rights, patterns of interaction among entities and allocation of decision rights. By adopting appropriate technics, tactics and procedures, an organization can enhance the three elements of C2 agility. This in turn will lead to an increase probability of mission success.

The two historical case studies:

Operation Anaconda, Afghanistan 2002. U.S. Airborne infantry, Special Forces and Afghan allies attempts to capture key Taliban and al-Qaeda leaders in the Shah-i-Khot valley. However, the al-Qaeda forces was much stronger than anticipated. The initial C2 approach by the U.S. forces was not appropriate for the mission and a new approach had to be improvised.

Operation Banner, Northern Ireland 1969 – 2007. The longest running campaign of the British Army in the 20th century. This was a highly complex campaign, conducted in a complex operational environment against an elusive opponent. During the campaign, the Security Forces developed special tactics that enhanced the three core elements of the C2 agility concept. This proved to be highly successful.

ABSTRACT. Since the last decade the impact of Information Operations (Info-Ops) on Battlefield is becoming huge; a comprehensive approach (for both Planning and Training) which is not just dealing with kinetic operations but also with other non-kinetic aspects of warfare (e.g. Social Media, information manipulation, etc.) is still one of a challenging (research) examination area for the upcoming years in order to improve the degree of reality and therefore commander decision and efficiency. Furthermore, integration of Command and Control (C2) systems in training and exercises has become very important (themed “Train as you fight”) in the last decade too. For this reason it is very important to display the battlefield situation, which is calculated by a simulation system, on the original C2-equipment. In this paper we will address the challenging issue for finding a standardized data exchange format between C4I and simulation systems. The challenge is to bring the complexity of the real world down to significant and measurable indicators which could be handled by constructive simulation systems as well. We will furthermore address the extension of the new C2SIM Logic Data Model (LDM) to deal with Info-Ops.

ABSTRACT. Over the past ten years a new approach to integrating coalition command and control (C2) systems with simulations into a complex system of systems has been developed. Teams from eight NATO nations have worked together toward a vision that a coalition will be able to assemble such a complex system rapidly in a standards-based environment called C2SIM, with the result that each nation uses the national C2 system with which it has trained and its forces are represented by a national simulation built around its capabilities and doctrine. This emerging capability is now working toward military operationalization. The C2SIM community has worked out an approach to distributed system-of-systems development that is well suited to the challenges we face. Co-locating national teams periodically for testing was expensive and slowed development, so over time the community gravitated toward using Internet interconnection for testing. A server site served as the core of a virtual private network, operating over the Internet. The culminating demonstration of the system of systems developed in this way also had client systems at multiple Internet locations. Having arrived at an effective approach for distributed development, the capability described in this paper was developed: a 24x7 testing/demonstration environment that enables any national team or combination of teams to test or demonstrate any of the component systems: C2, server, or simulation. Dubbed “C2SIM Sandbox,” this new capability is already the basis for multiple development and demonstration plans. The paper describes the design, implementation, and application of the Sandbox.

ABSTRACT. This paper describes how C2-Simulation (C2Sim) interoperability standards may be used to support a contemporary decentralised command and control system including reach-back to home base. Much previous work conducted in the C2Sim community has focused on the use of C2Sim standards to enable concurrent, multi-echelon, coalition and joint mission planning to be conducted using constructive simulations and analysis tools in support of the development and testing of operational plans and orders. Often the procedures needed in the contemporary operating environment call for more agile approaches to the development of plans; the command structures tend to be less formulaic, less hierarchical and less process-bound than conventionally deployed.

Evolving C2Sim standards provide a flexible means for conveying expression of intent and information exchange between the heterogeneous C2 systems typically used in coalition and multi-agency operations and supporting simulations. This paper will look at the special requirements needed to support these sorts of operations and how a test-bed or sand-box approach may be used to de-risk and evaluate the concepts developed. The paper will focus on the operational and conceptual elements of the system design and describe an example of such a decentralised C2 system supported by C2Sim-enabled simulation and analysis capability.

ABSTRACT. Due to the increased complexity and changing character of conflicts, and various technological developments, the Netherlands defence organisation believes that a transformation of the way the military operates is imperative and that operations in networked environments, so-called NetForce operations, offer a promising new approach. During NetForce operations power and influence is achieved by connections between the different military and civilian elements in a network. Within this hybrid network, command and control as we know it will change. The commander’s role shifts towards strategist, influencer and/or diplomat. Control will focus on (re-)setting the boundaries of freedom (constraints and restraints) and enabling subordinates rather than monitoring and (re-)directing subordinates ‘minute-to-minute’. The idea for a NetForce concept complements and elaborates the concepts of Network-centric Warfare (NCW), Netcentric Operations (NCO) and Network Enabled Capabilities (NEC), as most research efforts within the these fields were mainly related to technological and communication challenges. NetForce research is particularly focused on challenges in the organisational and human domain with topics like command, leadership, decision-making, organisation, collaboration, manoeuvre, and information management.

In order to support a structured approach to knowledge development for (future) NetForce concepts, a NetForce Framework was developed. Within the article, the NetForce concept is described as well as three applications for the NetForce Framework: structuring knowledge gained from desk research and literature reviews; analysing real-world cases in order to identify weaknesses and threats; and supporting the development and evaluation of new NetForce sub-concepts. Conclusions are drawn about the NetForce Framework’s usability for these applications.

ABSTRACT. The occasional dysfunctionality between the J5 (Plans) and J3 (Operation Execution) branches of a military headquarters are well known - planners work to longer time-frames and standardised processes and thus often have a mismatched engagement with time-poor operators who work to developing situations in theatre, each time doing things differently from the last. Ideally, the tight battle-rhythm of operators should feed into the longer cycles of the planners, and vice-versa. These effects flow-through to the other sections across a Joint Staff that interact with these two 'hemi-spheres' of the headquarters. Almost as challenging is being able to analyse this potential disconnect in a single model of headquarters. Apart from time-scales, the difference in level of irreducible complexity of tasks in the two branches calls for quite different modelling methodologies; common representation thus needs higher levels of abstractions from traditional task decomposition approaches. In this paper we apply to this problem a recent advance in the study of synchronisation on networks, namely representations of nested frequency distributions. This builds on earlier work by the author establishing the famous Kuramoto model of synchronisation of oscillators on networks as appropriate for Command and Control modelling. I will apply the nested frequency form of the model to a typical Joint Staff structure and explore how this allows identification of overloaded staff areas and friction points in the structure.

ABSTRACT. Because Army forces work in complex and contested environments, it is important to approach emulating the Army network from the point of view of studying the social, information and communication networks as a complete system. Previous work has shown that changing parameters in one network effects the behavior of other networks. We now seek to focus on the information network. Our goal in this work, specifically, is to understand how information travels through humans in Command and Control (C2) networks and use this understanding to diagnose bottlenecks and predict performance and scalability. We an agent-based simulation platform called the Experimental Laboratory for Investigating Collaboration, Information-sharing, and Trust (ELICIT), which simulates agent behaviors in an intelligence gathering and sharing scenario. Examining the simulation results, we can compare the effectiveness of different network topologies for supporting C2 and identify the components of human behavior that have the largest impact on C2.

ABSTRACT. Computer simulations have been widely used for evaluating several military activities in a budget-friendly fashion. They allow for countless parameterizations and are able to run scenarios in different complexity levels. These levels and parameters may not only refer to the physical models within the simulation, but also to the behaviors that govern both the agents and the environment itself. The way clouds move, or a flight pattern, are examples of movement behaviors, that account for a substantial part of the development of realism, but the simulation should also include another layer of intelligence which is responsible for the decision-making process within each entity, which will then call these other lower level behaviors. This work is part of an effort to properly model an air defense system, without implementing each of these behaviors, but the states that contain them. It focuses on a process that consists of modifications to a previously developed Petri-net model, which includes threat acquisition and assessment methods, adding a clearance scheme to model how the authorities will respond to different gravities of the situation. With all these sub-processes integrated, the main goal is to evaluate how the command and control structure affects the overall processing time, which will be a determinant factor on the effectiveness of the system with respect to the neutralization of the incoming threats. Lastly, metrics were developed to not only evaluate time-related data, but also whether the generated responses were compatible with the threats.

ABSTRACT. Defence Capability Management can be a cumbersome, long and very resource intensive activity. Within the context of limited resources and tight time constraints a new approach to Defence Capability Management was researched. Ensuring the integration and interaction between long term defence capability planning and short term operational planning is essential in ensuring an effective and efficient means of addressing defence capability management. A process was developed that ensure a close link, by means of using common data constructs based on the Joint Command Control and Collaboration Information Exchange Data Model, between long term capability requirements definition and the short term operational readiness planning. The process requires contextual inputs that are modelled by various means including capability profiles as well as scenario models. It is also essential that the process can provide impactful outputs during the execution of the process, in the absence of complete information, and not only at the end of a process run which could take years. Software applications were developed to support the capability management process and further enhance the efficiency and effective of the process. The approach was tested within landwards operation context and feedback on the results are provided.

ABSTRACT. Current trends are changing the way organizations operate and organize their processes in order to attain their objectives in a more complex, connected and interdependent society. Many organizations change towards a more networked structure or explore the possibilities of collaborating in one or more so called whole networks. Based on a literature search we selected a framework of Whelan (2015) to analyse three use cases: 1) community policing, 2) the organization of health care and 3) emergency services. These organizations are currently all in a transition to become more networked, or have recently completed this transition. Furthermore, as they all concern public services, lessons learned are likely to be relevant for the Defence organization. The use cases were evaluated on the following elements: 1) network structure, 2) network culture, 3) network policy; 4) network technology; and 5) network relationships. Overall, we concluded that there is no such thing as one size fits all. Aspects such as structure, leadership and policy highly depend on purpose and the context in which the work has to be performed. Moreover, organizations need to be flexible with regard to structure. However, despite this dependence of context and task we will discuss several overall recommendations that the Defense Organization needs to take into consideration in changing towards a (partly) networked organization.

ABSTRACT. In non-collaborative scenarios, especially for Military Forces, the Information Superiority is a privileged state in the Information Domain. But this privilege does not necessarily translate into better actions and effects, insofar is the superiority in the decisions which leads to operational advantage. There are many variables involved in the decision-making process, some intrinsically related to the Information Domain, such as Shared Situational Awareness and the process of extracting knowledge from Information, and others related to other domains, such as staff training and experience. For this reason, Information Superiority can only be seen as a potential for operational advantage, offering a valuable position to optimize the Decision Cycle by means of Knowledge Superiority. The purpose of this work is to discuss the aspects involved in the process of achieving Decision Superiority given that have Information Superiority. Ultimately, we propose the framework Decision Superiority from Information Superiority (DS-IS), that represents a high-level model of this transformation process, outlining the functions and variables that interact to achieve this goal.

ABSTRACT. All groups of people have interactions, both internal and external, which can be characterized, indexed, analyzed, and evolve/change. This applies to local, home, office, national, and international groups. The research and personnel area have helped with understanding this spectrum of interactions and the scale involved. The result is a community of models, techniques, and continuing research. A group model of internal dynamics is that of Tuckman (1965, 2001) – forming, storming, norming, and performing. Some aspects of internal group interactions are presented by Morieux and Tollman (2014) – that conflict and resolution seems to support improved performance. Graham Allison (1971) has presented large group interaction analysis through the Cuban Missile Crisis – rational actor, bureaucratic, and personality based. Chisolm (2012) has reviewed the Korean War successful Hungnam redeployment execution team adaptive effort. Rutledge, et al. (2014) (summarized by Kim, 2014), have researched the participant reward expectation physiological responses as correlated to risks, rewards, and the situation decisions of the participants. These areas and factors will be utilized through reflecting how different size organizations seem to respond to conflict and adapt toward other performance and interaction patterns. The paper will include a ‘happiness equation’ (ibid) analysis of the Hungnam redeployment team actions, along with group data analysis challenges with the intent to offer how both reward structure and group interactions can contribute to improved performance. Through the course of this paper’s discussion the author hopes to spur some insights, new research opportunities, or even improved organizational understanding and performance.

ABSTRACT. New information technologies (mobile Internet, cloud storage, social networking, Internet of Things) are transforming how we create new knowledge and understand the world. Military analysts cannot keep pace with the volume/variety/velocity of data collected from global sensors and multimedia sources (e.g., text, video, and images). Impressive gains in advanced analytics are emerging and are needed, in combination with new visualization technologies and approaches, to enable analysts full control over, and understanding of, the data relations. This will allow deriving meaningful, actionable conclusions from the massive amount of data available to them. This is particularly critical in a context where nations face an increasing threat of the global spread of terrorism, humanitarian crises/disaster, and public health emergencies. These threats are informed and/or influenced by the unprecedented rise of information sharing technologies and practices, even in the most underprivileged nations. In this new information environment, agile data algorithms, machine learning software, and alert mechanisms must be developed to exploit available data and to support timely and effective decision making. Yet these advanced technologies must be balanced with human awareness and understanding of the underlying context to accurately interpret machine-processed indicators and warnings and recommendations; human involvement will always remain critical in the decision process. In this paper, we will explore human dimension considerations (e.g., opportunities, challenges, constraints) of text, images, and video analytics, in the context of advanced C2 environments that rely on a wide variety of machine learning and artificial intelligence systems to support commanders’ decision making.

ABSTRACT. Military command and control tools are required to operate in increasingly complex environments and often inundate the operators with too much information. This effort proposes the application of Recommender Systems to provide decision support to operators through recommendations to reduce information overload, increase timeliness, and reduce the system complexity. This paper outlines an initial prototype of a recommender system for recommending ships for specific tasks or missions. A discussion is provided on how these types of systems may assist military planners in the future.

ABSTRACT. The pervasive use of social media has grown to over two billion users to date, and is commonly utilized as a means to share information and shape world events. Evidence suggests that passive social media usage (i.e., viewing without taking action) has an impact on the user’s perspective. This empirical influence over perspective could have significant impact on social events. Therefore, it is important to understand how social media contributes to the formation of an individual’s perspective. A set of experimental tasks were designed to investigate empirically derived thresholds for opinion formation as a result of passive interactions with different social media data types (i.e., videos, images, and messages). With a better understanding of how humans passively interact with social media information, a paradigm can be developed that allows the exploitation of this interaction and plays a significant role in future military plans and operations.

ABSTRACT. Decisional guidance can be defined as how a decision support system (DSS) guides or influences a user as they structure and execute their decision-making processes. There are several key distinctions in the definition of decisional guidance, for example, suggestive verses informative decisional guidance, and decisional guidance for structuring versus decisional guidance for executing the decision-making process. These distinctions have been adapted for a large-scale investigation on the effects of decision guidance in information-based problem solving (IBPS). A crowdsourced experiment hosted on the Volunteer Science web laboratory recruited participants from Amazon Mechanical Turk (AMT). The experiment was developed as a single-player against-the-clock game where the participant takes the role of a 35F intelligence analyst tasked with a Commander’s Critical Information Requirement (CCIR). Results of the crowdsourced experiment are described using a conceptual three-dimensional typology of decisional guidance proposed in DSS literature (Silver, 1991). Each dimension in the typology suggests a different set of questions such as “What is the target of the guidance?”, “What is the form of the guidance?”, and “What is the mode of the guidance?” in the experimental context of providing support for IBPS decisions an intelligence analyst might make during an operational scenario.

Silver, M. S. (1991). Decisional guidance for computer-based decision support. MIS Quarterly, 15(1), 105-122.

ABSTRACT. This paper reviews technology advances from different perspectives that could provide safe and cost effective achievable internetworking of intelligent things ecosystems with significant advantages to early adopters. Based on recent science and technology outlook, it appears that we might be at the cusp of practical specialized artificial intelligence in small devices. Similarly the transceiving capabilities of fifth generation cellular phones open access to advanced communication systems with capabilities not available before at low cost and with low energy demand. Future intelligent things will be more aware where they are and will be able to sense their environments either local radio spectrum time history, temperature, humidity and capture surrounding sounds. In addition smaller devices with high memory density and computing capabilities with low power demand make achievable advance security and encryption possible as well as local analytics which will provide more useful and actionable information to be shared. Moving some data analytics closer to alldomain sensors increases the ecosystem energy efficiency, reduces the burden on end users and central data centers. As much as possible, this paper will estimate the potential gain in terms of military mission success rate from the hypothetical adoption of such technologies that minimize operational cost and information management burden with extremely large numbers of data sources.

ABSTRACT. The growing adoption of Internet of Things (IoT) in the commercial sector in recent years has created a challenge for the military research community to evaluate the potential benefits of its tactical counterpart, which is referred to as Internet of Battlefield Things (IoBT). One of the key promises of IoBT-driven information frameworks are providing machine learning (ML) based algorithms that assist command and control (C2) systems in risk-informed decision making by processing the vast amount of information generated from the tactical field. In future military engagements, potential liabilities may result from actions based on decision where information was obtained from the military-owned IoBT as well as potentially unowned or compromised IoBT resources. Moreover, the variety of sensed data will introduce dimensions of variability (e.g. timing, scale, periodic-frequency, ergodicity, etc.) that will make accurate and efficient machine learning using conventional methods far more difficult than is the case today. Specifically, the IoBT data collected from sensors mounted on the soldiers has significant variability compared with data sensed from physical phenomena. In this paper, we study the particular challenges that ML algorithms are facing for processing human data within IoBT framework. As a case study, we present challenges faced in the development of an intelligent kinetic-signaling classification testbed and elaborate why these challenges are more significant in the C2 and tactical domains. We conclude by identifying critical research issues in the domain of developing tactical robust ML algorithms capable to augment risk-informed decision making in C2 systems.

ABSTRACT. The Internet-of-Things (IoT) promises to transform our society into smart environments that is environmentally aware. IoT applications cut across all societal domains, including military. Military organisations can exploit IoT applications in battlefields and operational theatres to improve situational awareness, mission performance and achieve information superiority. In this paper, it is presented a concept for the application of smart devices and IoT to future soldier systems (FSS) at the tactical domain. Relevant information to be gathered includes location, health status, motion and characteristics of the surrounding environment. Using as reference the Norwegian Home Guard Area Force use case and prior work conducted by FFI, a first proof-of-concept (PoC) is described, including results from a demonstration action incorporating real and simulated nodes. The paper concludes with the presentation of next steps for this work, namely the upcoming collaboration with the NATO IST-150 Group, aiming to produce recommendations towards achieving interoperability involving smart devices and IoT concepts.