Mark Austin

Ontologies of Time and Time-based Reasoning for MBSE of Cyber-Physical Systems

Our work is concerned with the development of Model-Based Systems Engineering (MBSE) procedures for the behavior modeling and design of Cyber-Physical Systems. This class of problems is defined by a tight integration of software and physical processes, the need to satisfy stringent constraints on performance, safety and a reliance on automation for the management of system functionality. To assure correctness of functionality with respect to requirements, there is a strong need for methods of analysis that can describe system behavior in terms of time, intervals of time, and relationships among intervals of time. Accordingly, this paper discusses temporal semantics and their central role in the development of a new time-based reasoning framework in MBSE for CPS. Three independent but integrated modules compose the system: CPS, ontology and time-reasoning modules. This approach is shown to be mostly appropriate for CPS for which safety and performance are dependent on the correct timebased prediction of the future state of the system. A Python-based prototype implementation has been created to demonstrate the capabilities of the ontological framework and reasoning engine in simple CPS applications.

An ontological framework for knowledge modeling and decision support in cyber-physical systems

Our work is concerned with the development of knowledge structures to support correct-by-design cyber-physical systems (CPS). This class of systems is defined by a tight integration of software and physical processes, the need to satisfy stringent constraints on performance and safety, and a reliance on automation for the management of system functionality and decision making. To assure correctness of functionality with respect to requirements, there is a strong need for system models to account for semantics of the domains involved. This paper introduces a new ontological-based knowledge and reasoning framework for decision support for CPS. It enables the development of determinate, provable and executable CPS models supported by sound semantics strengthening the model-driven approach to CPS design. An investigation into the structure of basic description logics (DL) has identified the needed semantic extensions to enable the web ontology language (OWL) as the ontological language for our framework. The SROIQ DL has been found to be the most appropriate logic-based knowledge formalism as it maps to OWL 2 and ensures its decidability. Thus, correct, stable, complete and terminating reasoning algorithms are guaranteed with this SROIQ -backed language. The framework takes advantage of the commonality of data and information processing in the different domains involved to overcome the barrier of heterogeneity of domains and physics in CPS. Rules-based reasoning processes are employed. The framework provides interfaces for semantic extensions and computational support, including the ability to handle quantities for which dimensions and units are semantic parameters in the physical world. Together, these capabilities enable the conversion of data to knowledge and their effective use for efficient decision making and the study of system-level properties, especially safety. We exercise these concepts in a traffic light time-based reasoning system.

Model-Based Systems Engineering Design and Trade-Off Analysis with RDF Graphs

Abstract Within the Semantic Web community, resource description frameworks (RDF) and logical reasoning engines work together to provide semantic support and reasoning for Web applications. This paper explores the use of RDF graphs for the representation of graphs of requirements and specification of design component properties. We show that the component selection design problem and associated trade-space analysis can be cast as a sequence inference analyses on RDF graphs. Inference procedures are provided for assessment of requirements in terms of component attribute values, identification of compatible component interface pairs, component selection to meet the system architecture requirements, and computation of system cost, performance and reliability. Our prototype implementation makes extensive use of Java and Python, and focuses on the satisfaction of requirements and component selection for a home theater design problem.

Ontology-enabled validation of connectivity relationships in a home theater system

This article describes a vision for team‐based synthesis of engineering systems, enhanced by technologies for ontology‐based computing, cast in a Semantic Web framework. Our long‐term research objective is to fully understand the extent to which relationships and constraints in ontology‐based descriptions of problem domains, working together with description logic reasoning engines, can influence and improve system‐level design procedures, particularly in the early stages of development where errors may have a significant long‐term impact, but if detected early are cheap to correct. As a first step, we develop a port–jack ontology for a home theater system and exercise rule sets for combinations of correct/incorrect connectivity. The model checking procedure begins with the formulation of a port–jack ontology that will describe allowable constraining relationships in the port and jack connectivity. Allowable types of connections are expressed in the form of domain restrictions.

Software Patterns for Traceability of Requirements to Finite State Machine Behavior

Abstract There is a growing class of engineering applications for which long-term managed evolution and/or managed sustainability is the primary development objective. The underlying tenet of our work is that neither of these trends will become fully mature without: (1) An understanding for how and why system entities are connected together, and (2) Formal procedures for assessing the correctness of system operations, estimating system performance, and understanding trade spaces involving competing design criteria. To address these concerns, during the past few years we have developed methodologies and tools for ontology-enabled traceability; that is, traceability mechanisms where requirements are connected to models of engineering entities by threading the traceability connection through one or more ontologies. In our proof-of-concept work the engineering entities were restricted to elements of system structure. But, of course, real engineering systems also have behaviors. This paper will report on research to understand the role that software patterns (e.g., model-view-controller) and mixtures of graph and tree visualization can play in the implementation of traceability mechanisms from requirements to elements of finite-state machine behavior (e.g., actions, states, transitions and guard conditions). We will present a simple lamp example.

Matrix and finite element stack machines for structural engineering computations with units

Abstract Despite the well known benefits of physical units, matrices, and matrix algebra in engineering computations, most engineering analysis packages are essentially dimensionless. This paper describes the design and implementation of matrix and finite element stack machines for Aladdin, a new computational environment that embeds units inside matrix and finite element calculations. Functionality of the Aladdin stack machine is illustrated by working step by step through the setup and execution of three examples: (1) Parsing and stack machine execution for x = 2 in; (2) Deflection analysis of a cantilever beam, and (3) Rollup maneuver for a long cantilever beam.

Platforms for Engineering Biomedical Experiments

Due to the highly stochastic nature of biological systems, the systematic design, validation, and verification of systems for biomedical experiments in laboratory and clinical applications are complex activities. This paper presents a platform framework for the modeling of these biological components in the context of system-level analysis. By integrating models of biological systems with those of physical engineering systems, one can obtain a set of potential architectures that satisfy the requirement specifications of the application. Such models can aid in the analysis of biomedical systems intended for applications in medical science, where the stochastic elements are the biological components themselves. A prototype application is presented that implements this platform framework for the development of a microfluidic assay device for the study of antibacterial treatments of bacterial biofilms. The results of our work indicate that looking forward, platforms will facilitate early validation and verification of biomedical devices, and enable the development of more efficient and effective experimental biomedical systems.

Model-Based Systems Engineering for design and automated operation of modern waterway systems

Waterway and canal systems are particularly cost effective in the transport of bulk and containerized goods to support global trade. Yet, despite these benefits, they are among the most under-appreciated of transportation engineering systems. Looking ahead, the long-term view is not rosy. Failures, delays, incidents, and accidents in aging waterway systems are doing little to attract the technical and economic assistance required for modernization and sustainability. We argue that programs for waterway and canal modernization and sustainability can benefit significantly from system thinking, supported by systems engineering techniques. To support this claim, we develop a framework for the Model-Based Systems Engineering (MBSE) design of modern waterways, especially canal systems. The proposed framework supports organizational, requirements and engineering models. Semi-formal modeling techniques are employed for the representation of project goals and scenarios and high-level models of behavior and structure. The essential features of this framework are highlighted in a case study where model-based systems engineering procedures are used for the design and analysis of a post-Panamax waterlock system. Formal verification procedures to demonstrate that essential system properties such as safety, liveliness and reachability are satisfied are currently under development.

Cyber-physical architecture for modeling and enhanced operations of connected-vehicle systems

This paper describes a cyber-physical architecture for behavior modeling and formal evaluation of safety properties in connected-vehicle systems. An ontology-based framework provides the description logic (DL) semantics and reasoning support needed for decision making. Safety properties are modeled as hard constraints, with their fulfillment determined through the synthesis and realization of predefined pathways on decision trees. To exercise the methodology, we consider the problem of ensuring system-level safety for a family of autonomous intelligent automobiles approaching a yellow traffic light.

Systems Engineering and Metabolic Engineering: A Side-by-Side Comparison

Abstract Cells of living organisms simultaneously operate hundreds or thousands of interconnected chemical reactions. Metabolic networks include these chemical reactions and the compounds participating in them. Metabolic engineering is a science centered on the analysis and purposeful modification of an organisms metabolic network toward a beneficial purpose, such as production of fuel or medicinal compounds in microorganisms. Unfortunately, there are problems with the design and visualization of modified metabolic networks due to lack of a standardized and fully developed visual modelling languages. The purposes of this paper are to propose a multi-level framework for the synthesis, analysis and design of metabolic systems, and then explore the extent to which abstractions from systems engineering (e.g., SysML) can complement and add value to the abstractions currently under development within the greater biological community (e.g. SBGN). The computational test-bed that accompanies this work is production of the anti-malarial drug artemisinin in genetically engineered Saccaharomyces cerevisiae (yeast).