Considerations for an Extended Framework for Interactive Epoch-Era Analysis

AbstractEpoch-Era Analysis (EEA) is a framework that supports narrative and computational scenario planning and analysis for both short run and long run futures. Currently EEA is being applied to frame problems faced by the DoD's Engineered Resilient Systems (ERS) efforts. Because of the large amount of data that must be analyzed when extending EEA to large-scale problems, such as those posed by DoD, a “big data” problem is introduced. This motivates the need for extensions to EEA methods that overcome the computational and human cognition issues that arise as a result. The research presented here describes exploratory development of Interactive Epoch-Era Analysis (IEEA) methods, including human interface and reasoning considerations for epoch and era characterizations, as well as single and multi- epoch and era analyses. Visualization techniques and methods for mitigating computational resource restrictions that facilitate improved decision-making are also presented

A Generalized Options-based Approach to Mitigate Perturbations in a Maritime Security System-of-Systems

Due to the complex and highly dynamic contexts in which systems operate nowadays, it has become crucial that, early in the architecting phase, System Architects take into account options to be utilized throughout the system's lifecycle to improve performance and lifecycle properties, such as flexibility. This paper introduces a preliminary approach that allows for the identification of relevant options, which are capable of mitigating perturbations negatively impacting a system of interest. The approach consists of the generation, evaluation and selection of relevant generalized options (enabling both changeability and robustness), and is demonstrated by application to a Maritime Security SoS case study. The inputs to the process are a list of desired design principles to implement in the system, and a list of perturbations that may affect the delivery of value to stakeholders (options are meant to mitigate perturbations). Four different metrics for option evaluation are proposed, together with techniques that can help during the process of selection of options.Massachusetts Institute of Technology. Systems Engineering Advancement Research Initiativ

Evaluating system change options and timing using the epoch syncopation framework

Complex engineering systems face many unknowns with respect to their operating contexts and time-varying stakeholder needs over their lifespan. A useful means for partitioning this problem is to consider a set of static snapshots of contexts with accompanying stakeholder needs over fixed periods of time, herein called “epochs.” Designs can be optimized towards delivering stakeholder utility in a specific epoch or across a variety of epochs. In order to consider the uncertain sequence of epochs experienced by a system, the Epoch Syncopation Framework (ESF) is introduced in this paper. This framework, using Monte Carlo analysis and Markov probability matrices, analyzes the execution of potential system “change mechanisms,” which alter a system over time to respond to epoch shifts. Through an analysis of design tradespaces, the ESF takes into account performance, schedule, cost, and uncertainty regarding experienced epoch shifts. The intended contributions of the ESF include a set of useful baseline designs, desirable change mechanisms, and strategies for executing change mechanisms across a system lifespan. The ESF is demonstrated through an application to an existing dataset containing designs for a “space tug” satellite including its set of potential epochs.Massachusetts Institute of Technology. Systems Engineering Advancement Research Initiativ

An Empirical Investigation of System Changes to Frame Links between Design Decisions and Ilities

Maintaining system performance in the presence of uncertainties in design and operating environments is both challenging and increasingly essential as system lifetimes grow longer. In response to perturbations brought on by these uncertainties, such as disturbances, context shifts, and shifting stakeholder needs, systems can continue to deliver value by being either robust or changeable. These lifecycle properties, sometimes called “ilities”, have been proposed as means to achieve system value sustainment in spite of changes in contexts or needs. Intentionally designing for these lifecycle properties is an active area of research, and no consensus has formed regarding how these and other “ilities” might trade off. This paper describes ongoing research that investigates empirical examples of system changes in order to characterize these changes and to develop a categorization scheme for framing and clarifying design approaches for proactively creating ilities in a system. Example categories from the data for system changes include: the perturbation trigger for the change, the type of agent executing the system change, and the valid lifecycle phase for execution. In providing a structured means to identify system change characteristics, this paper informs future research by framing possible relationships between ilities and design choices that enable them.Massachusetts Institute of Technology. Systems Engineering Advancement Research Initiativ

Investigating Relationships and Semantic Sets amongst System Lifecycle Properties (Ilities)

The ilities are properties of engineering systems that often manifest and determine value after a system is put into initial use (e.g. resilience, interoperability, flexibility). Rather than being primary functional requirements, these properties concern wider system impacts with respect to time and stakeholders. Over the past decade there has been increasing attention to ilities in industry, government and academia. Our research suggests that investigating ilities in sets may be more meaningful than study of single ilities in isolation. Some ilities are closely related and do in fact form semantic sets. Here, we use two methods to investigate over twenty ilities in terms of their prevalence and their interrelationships. We look for trends related to ilities of interest in relation to system type and an understanding of their collective use. First, we conducted a prevalence analysis of 22 ilities using both the internet as well as the Compendex/Inspec database as a source. We found over 1,275,000 scientific articles published between 1884 and 2010 and over 1.9 billion hits on the internet, exposing a clear prevalence-based ranking of ilities. Two questions we seek to address are: why and how are the ilities related to one another, and what can we do with this information. Initial steps to answer the first question include a 2-tupel-correlation matrix analysis that exposes the strongest relationships amongst ilities based on concurrent usage. Moreover, we conducted some preliminary experiments that indicate that a hierarchy of ilities with a few major groupings may be most useful. The overall objective for this research is to develop a formalframework and prescriptive guidance for effectively incorporating sets of ilities intothe design of complex engineering systems

Controlling Change Within Complex Systems Through Pliability

As systems become larger, more complex, and operate for longer periods of time, some change within the system often becomes inevitable. Particularly in systems of systems, with diverse stakeholders, evolutionary development and managerial independence, it is not unusual for constituent systems to change in form or the way they operate. Changeability, the ability of a system to change, is often considered to be a desirable attribute that allows systems to be robust and to adapt in response to changes in context. However, involuntary changes, such as those that occur as a result of a disturbance, are more often problematic than favorable. In some ways, the survivability of a system depends on its ability to prevent, mitigate and recover from unintentional changes within the system brought about by disturbances. For certain large systems of systems, where there are complex interactions and a diverse set of stakeholders, even voluntary changes may be frowned upon, since it may be an expensive and time consuming process to approve changes. This paper discusses pliability, a new “-ility” that places constraints on the changes a system is allowed to make. Pliability is the ability of a system to change, without “breaking” or violating an architecture that the system architects intended and validated. Like changeability, pliability increases robustness by allowing systems to voluntarily change in response to changing contexts, and increases survivability by increasing the likelihood that unintentional changes are still within the set of allowable instances. It also distinguishes allowable changes from those that would require validation and approval from decision makers, making it easier to actually implement those changes in large, complex systems

A taxonomy of perturbations: Determining the ways that systems lose value

Disturbances and disruptions, both internal and external to the system, are a major concern for system architects who are responsible for ensuring that their systems maintain value robustness no matter what occurs. These perturbations can have multiple causes and can affect a system in multiple ways. This paper presents a taxonomy of disturbances and disruptions to assist system architects and researchers in identifying the ways in which systems can fail to deliver value. By doing so, this taxonomy falls into a larger research effort to develop survivability design principles that will help system architects design systems that prevent, mitigate and recover from disturbances

Tree Island Response to Fire and Flooding in the Short-Hydroperiod Marl Prairie Grasslands of the Florida Everglades

Within the marl prairie grasslands of the Florida Everglades, USA, the combined effects of fire and flooding usually lead to very significant changes in tree island structure and composition. Depending on fire severity and post-fire hydroperiod, these effects vary spatially and temporally throughout the landscape, creating a patchy post-fire mosaic of tree islands with different successional states. Through the use of the Normalized Difference Vegetation Index (NDVI) and three predictor variables (marsh water table elevation at the time of fire, post-fire hydroperiod, and tree island size), along with logistic regression analysis, we examined the probability of tree island burning and recovering following the Mustang Corner Fire (May to June 2008) in Everglades National Park. Our data show that hydrologic conditions during and after fire, which are under varying degrees of management control, can lead to tree island contraction or loss. More specifically, the elevation of the marsh water table at the time of the fire appears to be the most important parameter determining the severity of fire in marl prairie tree islands. Furthermore, in the post-fire recovery phase, both tree island size and hydroperiod during the first year after the fire played important roles in determining the probability of tree island recovery, contraction, or loss

Multi-attributes tradespace exploration for survivability: Application to satellite radar

Multi-Attribute Tradespace Exploration (MATE) for Survivability is introduced as a general methodology for survivability analysis and demonstrated through an application to a satellite radar system. MATE for Survivability applies decision theory to the parametric modeling of thousands of design alternatives across representative distributions of disturbance environments. Survivability considerations are incorporated into the existing MATE process (i.e., a solution-generating and decision-making framework that applies decision theory to model-based design) by applying empirically-validated survivability design principles and value-based survivability metrics to concept generation and concept evaluation activities, respectively. MATE for Survivability consists of eight iterative phases: (1) define system value proposition, (2) generate concepts, (3) specify disturbances, (4) apply survivability principles, (5) model baseline system performance, (6) model impact of disturbances on dynamic system performance, (7) apply survivability metrics, and (8) select designs for further analysis. The application of MATE for Survivability to satellite radar demonstrates the importance of incorporating survivability considerations into conceptual design for identifying inherently survivable architectures that efficiently balance competing performance metrics of lifecycle cost, mission utility, and operational survivability