A Process Modelling Framework Based on Point Interval Temporal Logic with an Application to Modelling Patient Flows

This thesis considers an application of a temporal theory to describe and model the patient journey in the hospital accident and emergency (A&E) department. The aim is to introduce a generic but dynamic method applied to any setting, including healthcare. Constructing a consistent process model can be instrumental in streamlining healthcare issues. Current process modelling techniques used in healthcare such as flowcharts, unified modelling language activity diagram (UML AD), and business process modelling notation (BPMN) are intuitive and imprecise. They cannot fully capture the complexities of the types of activities and the full extent of temporal constraints to an extent where one could reason about the flows. Formal approaches such as Petri have also been reviewed to investigate their applicability to the healthcare domain to model processes. Additionally, to schedule patient flows, current modelling standards do not offer any formal mechanism, so healthcare relies on critical path method (CPM) and program evaluation review technique (PERT), that also have limitations, i.e. finish-start barrier. It is imperative to specify the temporal constraints between the start and/or end of a process, e.g., the beginning of a process A precedes the start (or end) of a process B. However, these approaches failed to provide us with a mechanism for handling these temporal situations. If provided, a formal representation can assist in effective knowledge representation and quality enhancement concerning a process. Also, it would help in uncovering complexities of a system and assist in modelling it in a consistent way which is not possible with the existing modelling techniques. The above issues are addressed in this thesis by proposing a framework that would provide a knowledge base to model patient flows for accurate representation based on point interval temporal logic (PITL) that treats point and interval as primitives. These objects would constitute the knowledge base for the formal description of a system. With the aid of the inference mechanism of the temporal theory presented here, exhaustive temporal constraints derived from the proposed axiomatic system’ components serves as a knowledge base. The proposed methodological framework would adopt a model-theoretic approach in which a theory is developed and considered as a model while the corresponding instance is considered as its application. Using this approach would assist in identifying core components of the system and their precise operation representing a real-life domain deemed suitable to the process modelling issues specified in this thesis. Thus, I have evaluated the modelling standards for their most-used terminologies and constructs to identify their key components. It will also assist in the generalisation of the critical terms (of process modelling standards) based on their ontology. A set of generalised terms proposed would serve as an enumeration of the theory and subsume the core modelling elements of the process modelling standards. The catalogue presents a knowledge base for the business and healthcare domains, and its components are formally defined (semantics). Furthermore, a resolution theorem-proof is used to show the structural features of the theory (model) to establish it is sound and complete. After establishing that the theory is sound and complete, the next step is to provide the instantiation of the theory. This is achieved by mapping the core components of the theory to their corresponding instances. Additionally, a formal graphical tool termed as point graph (PG) is used to visualise the cases of the proposed axiomatic system. PG facilitates in modelling, and scheduling patient flows and enables analysing existing models for possible inaccuracies and inconsistencies supported by a reasoning mechanism based on PITL. Following that, a transformation is developed to map the core modelling components of the standards into the extended PG (PG*) based on the semantics presented by the axiomatic system. A real-life case (from the King’s College hospital accident and emergency (A&E) department’s trauma patient pathway) is considered to validate the framework. It is divided into three patient flows to depict the journey of a patient with significant trauma, arriving at A&E, undergoing a procedure and subsequently discharged. Their staff relied upon the UML-AD and BPMN to model the patient flows. An evaluation of their representation is presented to show the shortfalls of the modelling standards to model patient flows. The last step is to model these patient flows using the developed approach, which is supported by enhanced reasoning and scheduling

Colored model based testing for software product lines (CMBT-SWPL)

Over the last decade, the software product line domain has emerged as one of the mostpromising software development paradigms. The main benefits of a software product lineapproach are improvements in productivity, time to market, product quality, and customersatisfaction.Therefore, one topic that needs greater emphasis is testing of software product lines toachieve the required software quality assurance. Our concern is how to test a softwareproduct line as early as possible in order to detect errors, because the cost of error detectedIn early phases is much less compared to the cost of errors when detected later.The method suggested in this thesis is a model-based, reuse-oriented test technique calledColored Model Based Testing for Software Product Lines (CMBT-SWPL). CMBT-SWPLis a requirements-based approach for efficiently generating tests for products in a soft-ware product line. This testing approach is used for validation and verification of productlines. It is a novel approach to test product lines using a Colored State Chart (CSC), whichconsiders variability early in the product line development process. More precisely, the vari-ability will be introduced in the main components of the CSC. Accordingly, the variabilityis preserved in test cases, as they are generated from colored test models automatically.During domain engineering, the CSC is derived from the feature model. By coloring theState Chart, the behavior of several product line variants can be modeled simultaneouslyin a single diagram and thus address product line variability early. The CSC representsthe test model, from which test cases using statistical testing are derived.During application engineering, these colored test models are customized for a specificapplication of the product line. At the end of this test process, the test cases are generatedagain using statistical testing, executed and the test results are ready for evaluation. Inxaddition, the CSC will be transformed to a Colored Petri Net (CPN) for verification andsimulation purposes.The main gains of applying the CMBT-SWPL method are early detection of defects inrequirements, such as ambiguities incompleteness and redundancy which is then reflectedin saving the test effort, time, development and maintenance costs

Executable system architecting using systems modeling language in conjunction with Colored Petri Nets - a demonstration using the GEOSS network centric system

Models and simulation furnish abstractions to manage complexities allowing engineers to visualize the proposed system and to analyze and validate system behavior before constructing it. Unified Modeling Language (UML) and its systems engineering extension, Systems Modeling Language (SysML), provide a rich set of diagrams for systems specification. However, the lack of executable semantics of such notations limits the capability of analyzing and verifying defined specifications. This research has developed an executable system architecting framework based on SysML-CPN transformation, which introduces dynamic model analysis into SysML modeling by mapping SysML notations to Colored Petri Net (CPN), a graphical language for system design, specification, simulation, and verification. A graphic user interface was also integrated into the CPN model to enhance the model-based simulation. A set of methodologies has been developed to achieve this framework. The aim is to investigate system wide properties of the proposed system, which in turn provides a basis for system reconfiguration --Abstract, page iii

Measurements, Models, Systems and Design

531 s.

The uses of process modeling : a framework for understanding modeling formalisms

There is wide-spread recognition of the urgent need to improve software processes in order to improve the performance of software organizations. Process models are essential in achieving understanding and visibility of processes and are important for other uses including the analysis of processes for improvement. It has been increasingly difficult to compare and evaluate the variety of process modeling formalisms that have appeared in recent years without a clear understanding of precisely for what they will be used. The contribution of this paper is to provide an understanding and a fairly comprehensive catalog of the applications of process modeling for which formalisms may be used. The primary mechanism for doing this is a guided tour of the literature on process modeling supplemented by recent industrial experience. In the paper, basic definitions concerning processes, process descriptions and process modeling are reviewed and then uses of process modeling are surveyed under the following headings: communication among process participants, construction of new processes, control of processes, process· analysis, and process support by automation. Comments are offered on paradigms for process modeling formalisms and directions for future work to permit evolution of a discipline of process engineering are given

A model driven approach to analysis and synthesis of sequence diagrams

Software design is a vital phase in a software development life cycle as it creates a blueprint for the implementation of the software. It is crucial that software designs are error-free since any unresolved design-errors could lead to costly implementation errors. To minimize these errors, the software community adopted the concept of modelling from various other engineering disciplines. Modelling provides a platform to create and share abstract or conceptual representations of the software system – leading to various modelling languages, among them Unified Modelling Language (UML) and Petri Nets. While Petri Nets strong mathematical capability allows various formal analyses to be performed on the models, UMLs user-friendly nature presented a more appealing platform for system designers. Using Multi Paradigm Modelling, this thesis presents an approach where system designers may have the best of both worlds; SD2PN, a model transformation that maps UML Sequence Diagrams into Petri Nets allows system designers to perform modelling in UML while still using Petri Nets to perform the analysis. Multi Paradigm Modelling also provided a platform for a well-established theory in Petri Nets – synthesis to be adopted into Sequence Diagram as a method of putting-together different Sequence Diagrams based on a set of techniques and algorithms

The DS-Pnet modeling formalism for cyber-physical system development

This work presents the DS-Pnet modeling formalism (Dataflow, Signals and Petri nets), designed for the development of cyber-physical systems, combining the characteristics of Petri nets and dataflows to support the modeling of mixed systems containing both reactive parts and data processing operations. Inheriting the features of the parent IOPT Petri net class, including an external interface composed of input and output signals and events, the addition of dataflow operations brings enhanced modeling capabilities to specify mathematical data transformations and graphically express the dependencies between signals. Data-centric systems, that do not require reactive controllers, are designed using pure dataflow models. Component based model composition enables reusing existing components, create libraries of previously tested components and hierarchically decompose complex systems into smaller sub-systems. A precise execution semantics was defined, considering the relationship between dataflow and Petri net nodes, providing an abstraction to define the interface between reactive controllers and input and output signals, including analog sensors and actuators. The new formalism is supported by the IOPT-Flow Web based tool framework, offering tools to design and edit models, simulate model execution on the Web browser, plus model-checking and software/hardware automatic code generation tools to implement controllers running on embedded devices (C,VHDL and JavaScript). A new communication protocol was created to permit the automatic implementation of distributed cyber-physical systems composed of networks of remote components communicating over the Internet. The editor tool connects directly to remote embedded devices running DS-Pnet models and may import remote components into new models, contributing to simplify the creation of distributed cyber-physical applications, where the communication between distributed components is specified just by drawing arcs. Several application examples were designed to validate the proposed formalism and the associated framework, ranging from hardware solutions, industrial applications to distributed software applications

Extra Functional Properties Evaluation of Self-managed Software Systems with Formal Methods

Multitud de aplicaciones software actuales están abocadas a operar en contextos dinámicos. Estos pueden manifestarse en términos de cambios en el entorno de ejecución de la aplicación, cambios en los requisitos de la aplicación, cambios en la carga de trabajo recibida por la aplicación, o cambios en cualquiera de los elementos que la aplicación software pueda percibir y verse afectada. Además, estos contextos dinámicos no están restringidos a un dominio particular de aplicaciones sino que se pueden encontrar en múltiples dominios, tales como: sistemas empotrados, arquitecturas orientadas a servicios, clusters para computación de altas prestaciones, dispositivos móviles o software para el funcionamiento de la red. La existencia de estas características disuade a los ingenieros de desarrollar software que no sea capaz de cambiar de modo alguno su ejecución para acomodarla al contexto en el que se está ejecutando el software en cada momento. Por lo tanto, con el objetivo de que el software pueda satisfacer sus requisitos en todo momento, este debe incluir mecanismos para poder cambiar su configuración de ejecución. Además, debido a que los cambios de contexto son frecuentes y afectan a múltiples dispositivos de la aplicación, la intervención humana que cambie manualmente la configuración del software no es una solución factible. Para enfrentarse a estos desafíos, la comunidad de Ingeniería del Software ha propuesto nuevos paradigmas que posibilitan el desarrollo de software que se enfrenta a contextos cambiantes de un modo automático; por ejemplo las propuestas Autonomic Computing y Self-* Software. En tales propuestas es el propio software quien gestiona sus mecanismos para cambiar la configuración de ejecución, sin requerir por lo tanto intervención humana alguna. Un aspecto esencial del software auto-adaptativo (Self-adaptive Software es uno de los términos más generales para referirse a Self-* Software) es el de planear sus cambios o adaptaciones. Los planes de adaptación determinan tanto el modo en el que se adaptará el software como los momentos oportunos para ejecutar tales adaptaciones. Hay un gran conjunto de situaciones para las cuales la propiedad de auto- adaptación es una solución. Una de esas situaciones es la de mantener al sistema satisfaciendo sus requisitos extra funcionales, tales como la calidad de servicio (Quality of Service, QoS) y su consumo de energía. Esta tesis ha investigado esa situación mediante el uso de métodos formales. Una de las contribuciones de esta tesis es la propuesta para asentar en una arquitectura software los sistemas que son auto-adaptativos respecto a su QoS y su consumo de energía. Con este objetivo, esta parte de la investigación la guía una arquitectura de tres capas de referencia para sistemas auto-adaptativos. La bondad del uso de una arquitectura de referencia es que muestra fácilmente los nuevos desafíos en el diseño de este tipo de sistemas. Naturalmente, la planificación de la adaptación es una de las actividades consideradas en la arquitectura. Otra de las contribuciones de la tesis es la propuesta de métodos para la creación de planes de adaptación. Los métodos formales juegan un rol esencial en esta actividad, ya que posibilitan el estudio de las propiedades extra funcionales de los sistemas en diferentes configuraciones. El método formal utilizado para estos análisis es el de las redes de Petri markovianas. Una vez que se ha creado el plan de adaptación, hemos investigado la utilización de los métodos formales para la evaluación de QoS y consumo de energía de los sistemas auto-adaptativos. Por lo tanto, se ha contribuido a la comunidad de análisis de QoS con el análisis de un nuevo y particularmente complejo tipo de sistemas software. Para llevar a cabo este análisis se requiere el modelado de los cambios din·micos del contexto de ejecución, para lo que se han utilizado una variedad de métodos formales, como los Markov modulated Poisson processes para estimar los parámetros de las variaciones en la carga de trabajo recibida por la aplicación, o los hidden Markov models para predecir el estado del entorno de ejecución. Estos modelos han sido usados junto a las redes de Petri para evaluar sistemas auto-adaptativos y obtener resultados sobre su QoS y consumo de energía. El trabajo de investigación anterior sacó a la luz el hecho de que la adaptabilidad de un sistema no es una propiedad tan fácilmente cuantificable como las propiedades de QoS -por ejemplo, el tiempo de respuesta- o el consumo de energÌa. En consecuencia, se ha investigado en esa dirección y, como resultado, otra de las contribuciones de esta tesis es la propuesta de un conjunto de métricas para la cuantificación de la propiedad de adaptabilidad de sistemas basados en servicios. Para conseguir las anteriores contribuciones se realiza un uso intensivo de modelos y transformaciones de modelos; tarea para la que se han seguido las mejores prácticas en el campo de investigación de la Ingeniería orientada a modelos (Model-driven Engineering, MDE). El trabajo de investigación de esta tesis en el campo MDE ha contribuido con: el aumento de la potencia de modelado de un lenguaje de modelado de software propuesto anteriormente y métodos de transformación desde dos lenguajes de modelado de software a redes de Petri estocasticas