A survey of swarming, a sub-topic of complexity. No mention of stigmergy though.
Some excerpts from Lars’ paper.
When the concept of stigmergy was first introduced in 1959 by the French entomologist Pierre-Paul Grassé (1959), an important step towards understanding the coordination of collective activities in social insects was made. Today, the concept of stigmergy is well established within the field of entomology (Theraulaz and Bonabeau, 1999). Turning from the study of insect behaviour to the study of human practice we find the concept of stigmergy to be less well established. However, criteria for applying the concept of stigmergy to the study of human practice are in fact readily emerging and a series of interesting and illuminating studies of stigmergy in a human context has been published (e.g. Christensen, 2008; Marsh & Onof, 2008; Ricci et al., 2007; Susi & Ziemke, 2001; Tummolini & Castelfrananchi, 2007; Parunak, 2006). This paper aims to contribute to this body of literature. Building on Grassé (1959), we will argue that that a coordinative effect can occur when human individuals act on the physical traces of work accomplished previously by others. That is, we will say that actors may coordinate and integrate their cooperative efforts by acting directly on the physical traces of work previously accomplished by others and that signs left or modifications made by individuals on artifacts may, given an appropriate context of practice, become meaningful to others and in turn inspire new actions on artifacts. This is how stigmergy may unfold in a human context. However, in connection to the study of stigmergy in a human context we need to ask a fundamental question before we “get ahead of ourselves.” The question is this: Does the concept of stigmergy add anything to our ability to account for the coordination of cooperative work in a human context? After all, stigmergy is a concept of coordination (Theraulaz and Bonabeau, 1999) and if we are to apply it to the study of human practice we have to ensure that it is not redundant in this context. That is, we have to make sure that there are no other concepts of coordination already having the analytical role that we are casting for the concept of stigmergy. This work has not been done so far (see related work section), and we shall address this challenge here. We shall proceed in the following manner. First we shall discuss related work. Secondly, we shall establish the nature of the concept of stigmergy in the study of human practice. Third, we shall compare the concept of stigmergy to three well-established concept of coordination in order to satisfy ourselves that stigmergy is not interchangeable with them. Fourth, we shall employ the concept of stigmergy in a study of construction work in order to explore the analytical utility of the concept in a human context. Finally, a conclusion and some perspectives will be offered.
In construction work, as in building design (Christensen, 2007; 2008), interdependent tasks may be partly integrated by virtue of individuals paying heed to the material evidence of work previously accomplished by others while performing their own tasks. Cooperative construction work tasks may be integrated through practices of stigmergy. As a case in point we shall consider the integration of cooperative work tasks pertaining to the construction of interior walls in a large building project. In the interior construction stage of a large building project a considerable number of partition walls are constructed. Partition walls are what divide the building into for instance units of office space. The construction of these walls is a cooperative work process involving a number of different trades such as carpenters, electricians and painters (see figure 2). The first and second frame shows the result of the carpenter’s initial efforts. The third frame, including insert, shows the work of the electrician in progress. Finally, the fourth frame depicts the closed wall ready for painting. The initial parts of a partition wall is constructed by a carpenter in the form of a frame made of light weight steel grinders fitted with plasterboards on the one side. At a later point in time, another actor, namely, an electrician will arrive and pay heed to the work carried out and seek to align the wiring of the electrical circuits with it. That is, the electrician will drill holes in the plasterboard to accommodate the electrical instillations and he or she will pull electrical cables through little holes in the vertical steel grinders of the frame and connect them to the electrical system as a whole. When the electrician is done and has left the scene, the carpenter returns to close the wall i.e. clad the second side of the wall in plasterboards in accordance with the previous work done. That is, the carpenter must take notice of the work previously performed by himself and the electrician as he seeks to put up the second round of plasterboards. Subsequently, the painter shows up to paint what the others have erected. At this point the wall in-the-making will have been worked on to consist of a steel frame, plasterboards on the first side, electrical instillations inside, and plasterboards on the second side. Finding the wall in this state the painter paints the wall with several coats of paint. In this manner the work ensemble including carpenter, electrician and painter all make distinct contributions towards the construction of the wall in accordance with their respective areas of expertise. We could say that the individual actor creates and changes the form of the wall in-the-making, not for the purpose of conveying a message, but simply as part of performing their individually allotted tasks, in turn another actor pays heed to and acts upon the material evidence of the work of others. This is partly how the cooperative work tasks pertaining to the construction of partition walls are integrated through practice of stigmergy. Perhaps to allow for full appreciation of the importance of this mode of coordination in building construction work, it would prudent to recall that no formal construct (e.g. architectural plan) exhaustively stipulates a concrete practice. Plans are underspecified with respect to that which is represented (Suchman, 1987), and architectural plans for the construction of for example partition walls are no exception. The actors have to “fill in the blanks” for themselves, so to speak, and acting on the evidence of work previously accomplished by others may be said to be one way of doing this. Furthermore, please bear in mind that architectural plans for specific building parts such as walls are not assembly manuals like those that come with for example IKEA furniture, rather architectural plans represent mainly how parts of the building it are supposed to look in the final state. Consequently, the assembly of for example partition walls is not covered in architectural plans. In addition, the pace of contemporary construction work is such that as soon as one actor (e. g. carpenter) has completed a task, time does not allow for much standing around and talking to the next actor (e. g. electrician) even though their tasks are interdependent and there are numerous details that need to be integrated. Of course articulation work through talk on the building site or in weekly coordination meetings may contribute to the integration of cooperative construction work tasks, but so may acting on the material evidence of work previously accomplished. The point is that in addition to various kinds of articulation work in meetings and with and without coordinative artifacts such as time schedules, cooperative construction work is coordinated by virtue of actors paying heed to the material evidence of work previously accomplished by others while performing their own tasks. At this juncture we may ask if the physical “evidence” of work may be promoted by the way in which the work is performed making it more straightforward for others to act on in practice of stigmergy? With reference to our case above, we may say that an electrician could for example install the electrical wiring and let a cable hang conspicuously visible in order to make the carpenter pay heed to it and afford it the required space as the wall is closed with the second layer of plasterboards (if the cables are completely hidden to the carpenters view he or she may accidentally put a nail through it with the nail gun as the second layer of plasterboards are mounted on the frame of the wall). This raises an interesting point: coordination through the material field of work may also be a matter of being mindful of the work that is to be performed by others looking forward in time, rather than only a matter of paying heed to work previously accomplished by others. At this point we may remind ourselves “the economy of logic […] dictates that no more logic is mobilized than is required by the needs of practice” (Bourdieu, 1992, p. 145). Following Bourdieu, we may say that the individual actors will engage in no more physical and cognitive effort than is practically necessary. That is, unless an actor has practical reasons for considering the situation from the perspective of others such as for example subsequent actors that may follow in practices of stigmergy, he or she will retain his or her own perspective and just carry out the work without though for the perspectives of others. Note that it is of course an empirical matter, something that differs from case to case, exactly how this plays out in practice. It is important to note that stigmergy, as a coordinative practice, is in not dependant on such forward looking mindfulness although it may be part of the larger set of practices. In sum, in construction work, cooperative work tasks are (partly) integrated through practices of stigmergy.
The concept of stigmergy was not originally developed in order to describe human practice, rather it was developed within the field of entomology i. e. the study of social insects. This study has raised and addressed a question central to any attempt to introduce the concept of stigmergy to the study of human practice: Does the concept of stigmergy add anything to our ability to account for the coordination of human cooperative work or is it simply interchangeable to already existing concepts? We have argued that it does add a new analytical perspective. Initially we suggested that in the context of human practice it is fruitful to understand stigmergy as a “heed” concept. That is, stigmergy refers to the phenomenon that distributed cooperative work tasks may be partly integrated by virtue of individuals paying heed to the material evidence of work previously accomplished by others while performing their own tasks. Based on this understanding of the concept of stigmergy in the context of human practice we explicitly compared and delimited the concept in relation to well-established concept describing human coordinative practices. We found that it differs from these concepts. We found that the concept of stigmergy is not interchangeable to well-established concepts of coordination such as articulation work, awareness and feedthrough. Finally, we explored the potential of the concept of stigmergy in an empirical study of coordinative practice in construction work in order to further investigate the utility of the notion of stigmergy as an analytical tool in the context of human practice. In regard to perspectives for further research, we may note that the three concepts of stigmergy, articulation work and awareness could amount to a trinity in the analytical toolbox for the description and analysis of the coordination of cooperative work – each concept pertaining to a unique yet interconnected mode of coordination of cooperative work.
Some extracts from Saurabh Mittal’s paper.
A natural system is not a monolithic system but a heterogeneous system made up of disparity and dissimilarity, devoid of any larger goal. The system just “is.” Examples of such systems include ant colonies, the biosphere, the brain, the immune system, the biological cell, businesses, communities, social systems, stock markets etc. Such systems are adaptable systems where emergence and self-organization are factors that aid evolution. These systems are classified as complex adaptive systems. According to Holland (2006, 1): “CAS are systems that have a large number of components, often called agents that interact and adapt or learn.”
In this article, we investigate CAS by looking at the scale of components, interactions between the components, and emergent properties that are manifested by such CAS. We will attempt to understand some of the common underlying properties, address the adaptive nature of such complex systems and illustrate how resilience is an inherent property of CAS.
CAS is occasionally modeled by means of agent-based models and complex network-based models. Multi-agent systems (MAS) is the area of research that deals with such study. However, CAS is fundamentally different from MAS in portraying features like self-similarity (scale-free), complexity, emergence and self-organization that are at a level above the interacting agents. A CAS is a complex, scale-free collectivity of interacting adaptive agents, characterized by high degree of adaptive capacity, giving them resilience in the face of perturbation. Indeed, designing an artificial CAS requires formal attention to these specific features. We will address these features and the formalisms needed to model CAS.
The discipline of modeling originated to understand natural phenomena. By developing abstractions, we can manage the apparent complexity, reuse it and enable these complex phenomena in artificial systems to our advantage. The discipline of executing this model on a time base is “simulation.” The task of decoding the original structure from manifested behavior is the holy grail of the modeling and simulation (M & S) enterprise (Zeigler, Praehofer, & Kim, 2000). The need for M & S to make progress in understanding CAS has been well acknowledged by Holland (1992). The task is to understand the gamut of rules that exist within and without a component and understand how the component deals with such multidimensional rules in an interactive environment. M & S is the only way one can understand, mimic and recreate a natural system. Most artificially modeled systems that exhibit complex adaptive behavior are driven by multi-resolution bindings and interconnectivity at every level of system behavior. To understand life is to “model”; to adapt is to survive in an environment, where both survival and environment are loaded concepts based on the guiding discipline.
Complexity is a phenomenon that is multivariable and multi-dimensional in a space-time continuum. Therefore, what we need is a framework that helps develop system structure and behavior in an abstract manner and that is component oriented so that the system can define its interactions based on the composition of a multi-level environment.
Stigmergy, the study of indirect interaction between network components in a persistent environment, explains certain emergent properties of a system. The network components include both the environment and the agent and both are persistent, i.e. both are situated in a space-time continuum and have memory. We take Stigmergic systems to be a subset of CAS and argue that stigmergic behavior is an emergent phenomenon too. Ultimately, we are trying to get a handle on how to formalize the property of “emergence.”
Discrete event abstraction has been studied at length by Bernard Zeigler throughout his illustrious career and his pioneering work on Discrete Event Systems (DEVS) formalism in 1970s (Ziegler, 1976). As a student, his perspectives on CAS were influenced by Holland. Ziegler’s approach to CAS has been through the quantization of continuous phenomena and how quantization leads to abstraction. Any CAS must operate within the constraints imposed by space, time, and resources on its information processing (Pinker, 1997). Evidence from neuronal models and neuron processing architectures and from fast and frugal heuristics, provide further support to the centrality of discrete event abstraction in modeling CAS when the constraints of space, time and energy are taken into account. Zeigler stated that discrete event models are the right abstraction for capturing CAS structure and behavior (Zeigler, 2004). In this article, we take the discipline of modeling CAS forward, by looking at the emergence aspect of CAS. We introduce DEVS and demonstrate how recent extensions still fall a little short in modeling CAS.
We first focus on the study of network science and how scale-free networks are inherently important to study complex interactions and hierarchical systems. In Section 3 we look at various types of interactions in a complex network. Section 4 we address the concepts of emergence and self-organization in detail and examine how a complex dynamic network facilitates such behavior. Section 5, a slight digression, provides an overview of DEVS theory. We return to the subject of dynamism in a complex adaptive network in Section 6 and show how DEVS theory is positioned to give modeling and simulation support to the subject. We describe various existing formal DEVS extensions that help model various features of stigmergy, emergence and CAS. Finally, in Section 7, we present some conclusions and pointers for future research.
Complexity is a multifaceted topic and each complex system has its own properties. However, some of the properties like high interconnectedness, large number of components, and adaptive behavior are present in most natural complex systems. We looked at the mechanism behind interconnectedness using network science that describes many natural systems in the light of power laws and self-similar scale-free topologies. Such scale-free topologies bring their own inherent properties to the complex system such that the entire system is subjected to the network’s structural and functional affordances.
It is largely unknown what makes a network evolve into a scale-free network, whether it is a top-down goal-driven phenomena or bottom-up causation or just an outcome of natural interactions. Two conditions have to be present for a network to evolve into a scale-free network: 1. incremental growth and 2. preferential attachment. We explored the notions of scale-free nature, strong and weak emergence, self-organization and stigmergic behavior in a complex adaptive system with persistent agents and persistent environment. We also related the concept of emergence to network science and presented arguments on how hubs and connectors are formed when a complex system is going through a critical phase. We argued that under any occurrence of both self-organized and emergent behavior together, the properties of scale-free network exist and one has to look at right level of abstraction in a multi-level system to witness the instance based interactions. We established that stigmergy displays strong emergence and is a specialized case of CAS. We also enumerated 18 properties of a CAS, 11 of which were properties of stigmergic systems.
We presented a high level view of DEVS theory and how its formal rigor is able to specify complex hierarchical systems. We described variants of dynamic structure and multi-level DEVS, and mapped it to some of the identified properties of CAS and stigmergy. We detailed the adaptive nature of complex system with DEVS Level of system specification and what it means to have dynamic adaptive behavior at different levels of a system. During the mapping process, we found that the following capabilities warrant formal attention to extend DEVS theory of complex systems to a theory of complex adaptive systems:
- How clusters are formed, hubs appear and evolve.
- How multi-level self-organization occurs.
- How strong emergence results in self-organization with an embedded observer capable of causal behavior at lower levels of hierarchy.
- How formal attention to coupling specification may provide additional abstraction mechanisms to model dynamic interconnected environment.
Finally, we recommended the augmentation of as the foundation for Stigmergic-DEVS, and investigation of both and ML-DEVS augmented together as a foundation for CAS-DEVS.