365 International Journal on Advances in Intelligent Systems, vol 10 no 3 & 4, year 2017, http://www.iariajournals.org/intelligent_systems/ 2017, © Copyright by authors, Published under agreement with IARIA - www.iaria.org Semantic Behavior Modeling and Event-Driven Reasoning for Urban System of Systems Maria Coelho and Mark A. Austin Department of Civil and Environmental Engineering, University of Maryland, College Park, MD 20742, USA E-mail: memc30@hotmail.com; austin@isr.umd.edu Mark Blackburn Stevens Institute of Technology, Hoboken, NJ 07030, USA E-mail: mblackbu@stevens.edu Abstract—Modern urban infrastructure systems are defined by spatially distributed network structures, concurrent subsystem- level behaviors, distributed control and decision making, and interdependencies among subsystems that are not always well understood. The study of the interdependencies within urban infrastructures is a growing field of research as the importance of potential failure propagation among infrastructures may lead to cascades affecting multiple urban networks. There is a strong need for methods that can describe the evolutionary nature of “system-of-systems” (SoS) as a whole. This paper presents a model of system-level interactions that simulates distributed system behaviors through the use of ontologies, rules checking, message passing mechanisms, and mediators. We take initial steps toward the behavior modeling of large-scale urban networks as collections of networks that interact via many-to-many association relationships. The prototype application is a collection of families interacting with a collection of school systems. We conclude with ideas for scaling up the simulations with Natural Language Processing. Keywords-Systems Engineering; Ontologies; Behavior Model- ing; Mediator; Network Communication. I. I NTRODUCTION This paper is concerned with the development of modeling abstractions, procedures, and prototype software for the be- havior modeling of urban systems of systems with ontologies, rules and message passing mechanisms. It builds upon our pre- vious work [1], [2] on distributed systems behavior modeling with semantic web technologies. A. Problem Statement The past century has been marked by outstanding advances in technology (e.g., the Internet, smart mobile devices, cloud computing) and the development of urban systems (e.g., trans- portation, electric power, waste-water facilities and water sup- ply networks, among others) whose individual resources and capabilities are pooled together to create new, more complex systems that offer superior levels of performance, extended functionality and good economics. While end-users applaud the benefits that these systems of systems afford, model-based systems engineers are faced with a multitude of new design challenges that can be traced to the presence of heterogeneous content (multiple disciplines), network structures that are spa- tial, multi-layer, interwoven and dynamic, and behaviors that are distributed and concurrent. Large-scale urban systems do not follow a standard cradle- to-grave lifecycle. Instead, the constituent domains within a city evolve over extended periods of time in response to external forces (e.g., the need for economic expansion) and disruptive events (e.g., the need for planning of relief actions in response to a natural disaster). In both cases, planning of urban operations is complicated by the large scale of modern cities, the large number of constituent behaviors, and multiple dimensions of interdependency among physical, cyber and geographic systems [3]. These facts are what makes cities “system of systems,” rather than just systems, and they change the very nature of systems design and management. For exam- ple, in order for the communication among the participating urban domains to occur in an orderly and predictable way, designers need to pay attention to the boundaries (or interfaces) of domains [4]. Similar concerns exit for the replacement of aging infrastructure. In his article on the topic of complex system failure “How Complex Systems Fail,” Cook discusses how complex systems are prone to catastrophic failure, due to the impractical cost of keeping all possible points of failure fully protected, and even identifying them all [5]. When part of a system fails, or perhaps an unexpected combination of localized failures occurs, there exists a possibility that the failure will cascade across interdisciplinary boundaries to other correlative infrastructures, and sometimes even back to the originated source, thus making highly connected systems more fragile to various kinds of disturbances than their independent counterparts. Figure 1 presents an overview of some generic interdependencies among key infrastructure sectors: oil and natural gas, electricity, transportation, water, and communica- tions. B. Scope and Objectives In order to understand how cascading failures might be best managed, it is necessary to have the ability to model events and the exchange of data/information at the interdependency boundaries, and to model their consequent effect within a subsystems boundary. This points to a strong need for new capability in modeling and simulation of urban infrastructure systems as system-of-systems, and the explicit capture of infrastructure interdependencies. We envision such a system having an architecture along the lines shown in Figure 2, and eventually, tools such as OptaPlanner [7] providing strategies for real-time control of behaviors, assessment of domain resilience and planning of recover actions in response to severe events. This paper presents a model of distributed system- level behaviors based upon the combined use of ontologies, rules checking, and message passing mechanisms, and explores