Flexibility, Complexity, and Controllability in Large Scale Systems

System structure is a key determinant of system behavior. There is a particularly strong link between a system’s structure and its flexibility – it’s capacity to respond to changes. Often, adding flexibility entails adding complexity. In this paper, we propose measures for a system’s complexity that are complementary to existing flexibility measures. Furthermore, flexibility often comes at the cost of some measure of control over the system’s behavior. We therefore propose a metric for system controllability that is complementary to our flexibility metric

Analogies Between Complex Systems and Phases of Matter

The behavior of a complex system in a changing environment is strongly affected by the system's architecture. We present an analogy between the major phases of matter (solid, liquid, gas) and three major generic architectures of complex systems: tree structures, layered structures and grid networks. This analogy is realized using a graph-based formalism, with nodes and edges in a given configuration. Solid materials are akin to tree structures, especially when we consider that most solids actually have cracks. Solids with cracks between their components can be modeled by nodes (representing each component) and their interconnection, leading to a tree structured hierarchy. Gases made up of molecules can be modeled by nodes (the molecules) with local interconnections representing nearby molecules in space, thus forming a grid network. Liquids can form layers as in a mixture of oil and water. We represent this by connections that are densely horizontal within layers as well as sparsely vertical between layers. A key issue for complex systems is the ease by which they may be changed, which we call the system’s flexibility. Our definition of flexibility indicates that tree structures, like solids, are relatively inflexible and that grid networks, like gases, are extremely flexible, possibly leading to loss of control and chaotic behavior. Like liquids, layered systems are intermediate in flexibility and controllability. Solids, even with cracks, are relatively difficult to modify, whereas gases change internal form so quickly that they can only be constrained; not controlled. Liquids are intermediate in their ability to change form internally. Just as heating solids can lead to liquids, and heating liquids can result in gases, we shall present transformations in the interconnection structure of systems, analogous to heating, that change tree structures into layered ones and layered structures into networks

Gist and Verbatim in Narrative Memory

A major concern regarding the study of narratives regards how they are indexed and retrieved. This is a question which touches on the structure of human memory in general. Indeed, if narratives capture the substance of human thought, then data that we have already collected regarding human memory is of central importance to the computational study of narrative. Fuzzy Trace Theory assumes that memory for narrative is simultaneously stored at multiple levels of abstraction and, whenever possible, decision-makers interpret a stimulus qualitatively and therefore operate on a simple - typically categorical - "gist" representation. Here, we present a computational model of Fuzzy Trace Theory applied to explain the impact of changes in a narrative upon risky-choice framing effects. Overall, our theory predicts the outcome of 20 experimental effects using only three basic assumptions: 1) preference for lowest level of gist, that is, categorical processing; 2) decision options that fall within the same categorical description are then interpreted using finer-grained (ordinal or verbatim) distinctions; and 3) once the options are mentally represented, decision preferences are generated on the basis of simple positive vs. negative valences stored in long-term memory (e.g., positive value for human lives). A fourth assumption - that negatively-valenced decision options are preferentially converted to positive decision options - is used when categories are not otherwise comparable

Decision-Making in the Political and Technical Environments

Mutual misunderstanding between decision-makers in the political and technical environment leads to programs that experience cost overruns, schedule delays and, often, cancellation. This paper compares and contrasts the determinants of decision-making in the technical and political realms, with the intention of demonstrating how these decisions translate to cost, schedule and performance parameters. Studies of those elements that are most salient to the policy maker are informed by the political science literature. In particular, studies of administrative, bureaucratic and Congressional decision-making are instructive in determining how an engineering system interacts with the political realm. So as to lend concreteness to this analysis, we focus on NASA’s interactions with Congress surrounding the Vision for Space Exploration, announced by President Bush on January 14th, 2004

A method for analysis of expert committee decision-making applied to FDA medical device panels

Thesis (Ph. D.)--Massachusetts Institute of Technology, Engineering Systems Division, 2010.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student submitted PDF version of thesis.Includes bibliographical references (p. 254-263).Committees of experts are critical for decision-making in engineering systems. This is because the complexity of these systems requires that information is pooled from across multiple specialties and domains of knowledge. The social elements of technical decision-making are not well understood, particularly among expert committees. This is largely due to a lack of methodology for directly studying such interactions in real-world situations. This thesis presents a method for the analysis of transcripts of expert committee meetings, with an eye towards understanding the process by which information is communicated in order to reach a decision. In particular, we focus on medical device advisory panels in the US Food and Drug Administration. The method is based upon natural language processing tools, and is designed to extract social networks in the form of directed graphs from the meeting transcripts which are representative of the flow of information and communication on the panel. Application of this method to a set of 37 meetings from the FDA's Circulatory Systems Devices Panel shows the presence of numerous effects. Prominent among these is the propensity for panel members from similar medical specialties to use similar language. Furthermore, panel members who use similar language tend to vote similarly. We find that these propensities are correlated - i.e., as panel members' language converges by medical specialty, panel members' votes also converge. This suggests that voting behavior is mediated by membership in a medical specialty and supports the notion that voting outcome is, to some extent, dependent on an interpretation of the data associated with training, particularly when a small number of interpretations of the data are possible. Furthermore, there is some preliminary evidence to suggest that as clinical trial data ambiguity and difficulty of decisionmaking increases, the strength of the mediating effect of medical specialty decreases. Assuming a common decision is reached, this might indicate that committee members are able to overcome their specialty perspective as the committee jointly deals with hard problems over longer periods of time. In cases where the panel's vote is split, a lack of linguistic coherence among members of the same medical specialty correlates with a lack of linguistic coherence among members who vote the same way. This could be due to the presence of multiple interpretations of the data, leading to idiosyncratic or value-based choice. We also find that voting outcome is associated with the order in which panel members ask questions - a sequence set by the committee chair. Members in the voting minority are more likely to ask questions later than are members in the voting majority. Voting minority members are also more likely to be graph sinks (i.e., nodes in a social network that have no outflow) than are voting majority members. This suggests an influence mechanism on these panels that might be associated with framing - i.e., later speakers seem to be less able to convince other panel members to discuss their topics of interest contributing to these members' minority status. These results may have some relation to FDA panel procedures and structure. Finally, we present a computational model that embodies a theory of panel voting procedures. Model results are compared to empirical results and implications are drawn for the design of expert committees and their associated procedures in engineering systems.by David André Broniatowski.Ph.D

Political sustainability in the vision for space exploration : articulating the policy-technology feedback cycle

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics; and, (S.M.)--Massachusetts Institute of Technology, Engineering Systems Division, Technology and Policy Program, 2006.Vita. Page 154 blank.Includes bibliographical references (p. 146-153).It is often difficult to forecast the future budgetary environment for today's space systems. Indeed, multiple NASA missions and programs have been put into jeopardy or canceled outright, due to discrepancies between the expected and actual lifecycle costs. This has resulted in the loss of billions of dollars in taxpayer money spent on false starts. It is therefore in the best interests of all stakeholders, including NASA and the U.S. Congress, to arrive at a solution which will allow NASA's space exploration endeavors to be funded at a politically sustainable level. Understanding the mechanisms and processes by which a program may exhibit politically sustainability is of paramount importance to the space exploration enterprise. In particular, budgetary sustainability has proven to be a driver for The President's Vision for Space Exploration, which instructs NASA to "Implement a sustained and affordable" space exploration program. NASA, as a federal agency, is dependent upon the support of many stakeholders within the US political system, especially the President and members of Congress. Thus, a politically sustainable program must address the needs of these stakeholders.(cont.) Based upon strategies for agency-Congress interaction that are derived from the existing political science literature, this thesis proposes to translate policy directives into technical constraints or requirements for the Vision for Space Exploration. The effects of these changes in the technical system are then traced back to determine how they effect the political environment, articulating a feedback-loop that crosses between the political and technical realms.by David André Broniatowski.S.M

Identifying Nuances in Fake News vs. Satire: Using Semantic and Linguistic Cues

The blurry line between nefarious fake news and protected-speech satire has been a notorious struggle for social media platforms. Further to the efforts of reducing exposure to misinformation on social media, purveyors of fake news have begun to masquerade as satire sites to avoid being demoted. In this work, we address the challenge of automatically classifying fake news versus satire. Previous work have studied whether fake news and satire can be distinguished based on language differences. Contrary to fake news, satire stories are usually humorous and carry some political or social message. We hypothesize that these nuances could be identified using semantic and linguistic cues. Consequently, we train a machine learning method using semantic representation, with a state-of-the-art contextual language model, and with linguistic features based on textual coherence metrics. Empirical evaluation attests to the merits of our approach compared to the language-based baseline and sheds light on the nuances between fake news and satire. As avenues for future work, we consider studying additional linguistic features related to the humor aspect, and enriching the data with current news events, to help identify a political or social message.Comment: Accepted to the 2nd Workshop on NLP for Internet Freedom (NLP4IF): Censorship, Disinformation, and Propaganda. Co-located with EMNLP-IJCNLP 201