Agent-based modelling of paratransit as an intelligent complex adaptive system to improve efficiency

Thesis (PhD)--Stellenbosch University, 2021.ENGLISH ABSTRACT: Urban residents in Sub-Saharan Africa (SSA) face mobility challenges that limit theiraccess to jobs, services, markets, and socioeconomic opportunities. In most SSA cities,public transport is predominantly provided by the inefficient paratransit system – a flex-ible mode of passenger transport consisting of privately-owned, low-capacity unscheduledminibuses and motorcycle taxis. There is growing interest among city authorities andurban transport researchers in addressing the inefficiency problem associated with para-transit. Several approaches, such as complete overhaul to bus rapid transit (BRT), andphased banning of paratransit from the cities have previously been proposed and con-comitant implementation projects started. However, most of such projects have eitherfailed to take off, or they have stalled. This is likely because of the huge capital invest-ment required, the unique social and cultural dynamics associated with “third world”countries, and urban sprawl due to poor city planning. This study departs from the com-mon perspective held by several researchers and city authorities who view paratransit as“chaotic”, thus, the justification for its total overhaul and banning. Instead, this studyaims to leverage the beneficial aspects of existing paratransit – such as flexibility, demand-responsiveness and near-ubiquitous coverage – with the elusive objective of achieving amore efficient paratransit state as a result.Through theoretical modelling, field study and experimental approaches, this studyaimed to improve the efficiency of minibus taxis paratransit systems. The theoretical mod-elling work involved modelling paratransit systems as complex adaptive systems (CAS)and developing an agent-based model (ABM) for minibus taxi operations in an organically-evolved paratransit setting. The field study involved an in-depth investigation of minibustaxi operations in Kampala’s paratransit system, and collection and analysis of minibustaxi movement data that was used to validate the agent-based model. The experimen-tal approaches involved three separate simulation experiments, simulating the minibustaxi transportation dynamics with varying levels of agents’ intelligence and situational awareness. Machine learning methods, such as random forests and convolutional neuralnetworks were used to train agents in the subsequent simulation experiment to improvetheir intelligence during decision making. At each stage, several efficiency metrics’ valuessuch as passenger waiting time and minibus taxi occupancy were collected. The resultsfrom the experiments showed that there was an improvement in the overall efficiency ofthe minibus taxi paratransit system. For instance, the average passenger waiting time re-duced from 1.2 hours to 30 minutes, indicating a 55% improvement. Whereas the averageminibus taxi occupancy increased from 42% to 51%, indicating a 21% improvement. Ac-cordingly, we concluded that improving the micro-level agents’ intelligence and situationalawareness, results in an overall increase in the efficiency of the paratransit system.To the transportation researchers, we recommend further work on using ABM toinclude other modes of paratransit transport such as the three-wheeled rickshaws andmotorcycle taxis (boda bodas). To the city authorities, we recommend the integration ofsmart mobility and ICT applications into the paratransit ecosystem to support journeyplanning, booking, scheduling, and fare collection.AFRIKAANSE OPSOMMING: Stedelike inwoners in Afrika Suid van die Sahara (SSA) word gekonfronteer met mo-biliteitsuitdagings wat hul toegang tot werk, dienste, markte en sosio-ekonomiese geleen-thede beperk. In die meeste SSA-stede word openbare vervoer oorheersend aangebieddeur die ondoeltreffende paratransit-stelsel -’n buigsame manier van passasiersvervoerwat bestaan uit private lae-volume busse en huur-motorfietse. Daar is toenemende be-langstelling onder stadsowerhede en navorsers van stedelike vervoer om die ondoeltref-fendheidsprobleem so eie aan paratransit. Verskeie benaderings, soos byvoorbeeld dievolledige opknapping van busvervoer (BRT) en ’n gefaseerde verbod op paratransit instede, is voorheen voorgestel en verwante implementeringsprojekte is van stapel gestuur.Die meeste van hierdie projekte het egter nie daarin geslaag om te begin nie, of hulleis gestaak. Dit is waarskynlik as gevolg van die groot kapitaalinvestering wat benodigword, die unieke sosiale en kulturele dinamika wat verband hou met lande van die ”derdewˆereld” en stedelike uitbreiding as gevolg van swak stadsbeplanning.Hierdie studie wyk af van die algemene perspektief wat deur verskeie navorsers en stad-sowerhede gehou word, wat paratransit as “chaoties” beskou, en dus van die regverdigingvir die totale opknapping en verbod daarvan. In plaas daarvan beoog hierdie studie omdie voordelige aspekte van paratransit te versterk - soos buigsaamheid, aanvraagresponsi-witeit en byna alomteenwoordige dekking - met die hoop om ’n doeltreffender paratransit-staat as gevolg daarvan te bewerkstellig.Deur middel van teoretiese modellering, veldstudies? en eksperimentele benaderings,het hierdie studie ten doel gehad om die doeltreffendheid van minibustaxi-paratransitstelselste verbeter. Die teoretiese modelleringswerk behels die modellering van paratransitstelselsas komplekse aanpasbare stelsels (CAS) en die ontwikkeling van ’n agent-gebaseerde model(ABM) vir minibustaxibedrywighede in ’n organies-ontwikkelde paratransit-omgewing.Die veldstudie behels ’n diepgaande ondersoek na minibustaxibedrywighede in Kampala se paratransit-stelsel, en versameling en ontleding van minibustaxibewegingsdata wat ge-bruik is om die agent-gebaseerde model te bekragtig. Die eksperimentele benaderings hetdrie afsonderlike simulasie-eksperimente behels, wat die minibustaxi-vervoerdinamika metverskillende vlakke van agente se intelligensie en situasiebewustheid simuleer. Masjienleer-metodes soos ewekansige woude en evolusionˆere neurale netwerke is gebruik om agente indie daaropvolgende simulasie-eksperiment op te lei om hul intelligensie tydens besluitnem-ing te verbeter. In elke stadium is verskeie waardes vir doeltreffendheid soos die passasier-swagtyd en die besetting van minibustaxi’s versamel. Die resultate van die eksperimentehet getoon dat die algehele doeltreffendheid van die minibus-paratransitstelsel verbeterhet. Byvoorbeeld, die gemiddelde passasierwagtyd verminder van 1,2 uur tot 30 minute,wat dui op ’n 55% verbetering. Terwyl die gemiddelde besetting van minibustaxi van 42%tot 51% gestyg het, wat dui op ’n verbetering van 21%.Gevolglik het ons tot die gevolgtrekking gekom dat die verbetering van die intelligensieen situasiebewustheid van die mikrovlakagente tot ’n algehele toename in die doeltreffend-heid van die paratransitstelsel lei.Vir die vervoernavorser beveel ons verdere ABM-werk aan om ander maniere vanparatransit-vervoer soos die driewiel-riksja’s en motorfiets-taxi’s (boda bodas) in te sluit.Aan die stadsowerhede beveel ons die integrasie van slim mobiliteit- en IKT-toepassingsaan in die paratransit-ekosisteem om reisbeplanning, bespreking, skedulering en tariefin-vordering te ondersteun.Doctora

Management Aspects of Software Clone Detection and Analysis

Copying a code fragment and reusing it by pasting with or without minor modifications is a common practice in software development for improved productivity. As a result, software systems often have similar segments of code, called software clones or code clones. Due to many reasons, unintentional clones may also appear in the source code without awareness of the developer. Studies report that significant fractions (5% to 50%) of the code in typical software systems are cloned. Although code cloning may increase initial productivity, it may cause fault propagation, inflate the code base and increase maintenance overhead. Thus, it is believed that code clones should be identified and carefully managed. This Ph.D. thesis contributes in clone management with techniques realized into tools and large-scale in-depth analyses of clones to inform clone management in devising effective techniques and strategies. To support proactive clone management, we have developed a clone detector as a plug-in to the Eclipse IDE. For clone detection, we used a hybrid approach that combines the strength of both parser-based and text-based techniques. To capture clones that are similar but not exact duplicates, we adopted a novel approach that applies a suffix-tree-based k-difference hybrid algorithm, borrowed from the area of computational biology. Instead of targeting all clones from the entire code base, our tool aids clone-aware development by allowing focused search for clones of any code fragment of the developer's interest. A good understanding on the code cloning phenomenon is a prerequisite to devise efficient clone management strategies. The second phase of the thesis includes large-scale empirical studies on the characteristics (e.g., proportion, types of similarity, change patterns) of code clones in evolving software systems. Applying statistical techniques, we also made fairly accurate forecast on the proportion of code clones in the future versions of software projects. The outcome of these studies expose useful insights into the characteristics of evolving clones and their management implications. Upon identification of the code clones, their management often necessitates careful refactoring, which is dealt with at the third phase of the thesis. Given a large number of clones, it is difficult to optimally decide what to refactor and what not, especially when there are dependencies among clones and the objective remains the minimization of refactoring efforts and risks while maximizing benefits. In this regard, we developed a novel clone refactoring scheduler that applies a constraint programming approach. We also introduced a novel effort model for the estimation of efforts needed to refactor clones in source code. We evaluated our clone detector, scheduler and effort model through comparative empirical studies and user studies. Finally, based on our experience and in-depth analysis of the present state of the art, we expose avenues for further research and development towards a versatile clone management system that we envision

Views and concerns and interrelationships : Lessons learned from developing the multi-View software engineering environment PIROL

Software-Entwicklungsumgebungen sind komplexe Systeme mit besonderen Anforderungen an Modularität und Anpaßbarkeit. Diese Arbeit beschreibt die Entwicklung der Umgebung PIROL. Die Beschreibung ist dabei in eine Abfolge der folgenden 12 Themen gegliedert. (1) Metamodellierung ist das Grundkonzept, nach dem PIROL seine Daten gemäß einem objektorientierten Datenmodell zerlegt, so daß beliebige Werkzeuge auch auf die Daten anderer Werkzeuge auf sinnvolle Art und Weise zuzugreifen können. (2) Das Metamodell wird zur persistenten Speicherung der Daten auf Konzepte des Repositories H-PCTE abgebildet. (3) Die Granularität eines Metamodells ist für die Effektivität und Effizienz des Gesamtsystems entscheidend. PIROL unterstützt hybride Modellierung als Kompromiß beider Extreme. (4) Durch Methoden des Metamodells wird Verhaltensmodellierung für verschiedenste Aufgaben unterstützt. (5) Ausnahmebehandlung wird systematisch unterstützt. (6) Verschiedene Mechanismen zur Wahrung der Datenintegrität sind enthalten. (7) Das System wurde nach einer Client-Server Architektur entwickelt, deren zentrale Komponente eine "Workbench" ist, die die Repository-Sprache Lua/P ausführt. (8) Steuerungsintegration erlaubt durch verteilte Steuerflüsse das enge Zusammenspiel lose gekoppelter Komponenten. (9) Die koordinierte Zusammenarbeit mehrerer Benutzer wird unterstützt. (10) Die logische Unabhängigkeit von Werkzeugen wird durch das neue Konzept der Dynamic View Connectors erreicht. (11) Allgemeine Dienste sind in der Umgebung einheitlich verfügbar. (12) Das System unterstützt die Weiterentwicklung. All diese Themengebiete sind sehr eng miteinander verzahnt und die Darstellung ist zu großem Teil der gegenseitigen Beeinflussung gewidmet. Es wird gezeigt, wie eine Großzahl der Entwurfsentscheidungen genau aus diesen Beeinflussungen motiviert sind. Die Beschreibung folgt damit dem Konzept der "Concern Interaction Matrix", das hier zur Bewältigung von Komplexität vorgeschlagen wird. Dabei werden Charakteristika einzelner Anliegen und einzelner Zusammenhänge herausgearbeitet. Die Beschreibung PIROLs wird durch die Liste der integrierten Werkzeuge, Ansätze von Laufzeit-Messungen und einige Betrachtungen zur Beurteilung abgerundet. Abschließend werden verschiedene Konzepte rund um den Begriff "Sichten" erörtert. Sichten sind ein zentrale Anliegen von PIROL. Außerdem generalisiert die Diskussion über die mehrdimensionale Darstellung des Hauptteiles. Es werden Begrifflichkeit, Konzepte und Techniken für Sichten in der Softwaretechnik vorgestellt und diskutiert. Dabei wird die Brücke geschlagen von Sichten in objektorientierten Datenbanken, über aspekt-orientierte Softwareentwicklung bis hin zum allgemeinen "Concern Modeling", zu dem die o.g. Methode einen Beitrag leisten soll. Sichten werden dabei als ein zentrales Konzept der Softwaretechnik neben Abstraktion und Zerlegung beurteilt. Dynamic View Connectors sind ein wesentlicher Beitrag von PIROL, durch den Datenbanksichten und aspektorientierte Programmierung zusammengeführt werden. Zwar ist der Sichten-Begriff längst nicht so scharf definiert, wie die Begriffe Abstraktion und Zerlegung, aber gerade die Überlappungen und Diskrepanzen, die durch Sichten abgebildet werden können, machen dies Konzept zu einem starken Strukturierungsprinzip, das zwar einigen Aufwand zur Behandlung von Inkonsistenzen erfordert, aber andererseits hilft, komplexe Systeme handhabbar und wartbar zu gestalten.Software engineering environments are complex systems with special requirements regarding modularity and adaptability. This thesis describes the development of the environment PIROL. The description is structured as a sequence of the following 12 concerns: (1) Meta modeling is the basic concept by which PIROL decomposes its data in accordance to an object-oriented data model. This allows arbitrary tools to access data of other tools in a meaningful way. (2) For persistent storage the model is mapped to the concepts of the repository H-PCTE. (3) The granularity of a meta model determines effectiveness and efficiency of the system. PIROL supports hybrid modeling as a compromise between extremes. (4) By methods of the meta model behavior modeling is supported for a wide range of tasks. (5) Exception handling is supported systematically. (6) Several mechanisms for preserving data integrity are integrated. (7) The system follows a client-server architecture. As its, central component the "workbench" executes the repository language LuaP. (8) Control integration allows for close cooperation of loosely coupled components by means of distributed control flows. (9) The coordinated cooperation of multiple users is supported. (10) Logical independence of tools is achieved by the novel concept of Dynamic View Connectors. (11) Common services are available throughout the environment in a uniform way. (12) The system is prepared for evolution. All these concerns are tightly interlocked. A considerable share of the presentation is dedicated to such mutual interactions. Is is shown, how a large number of design decisions is motivated exactly by these interactions. The description follows the concept of a "Concern Interaction Matrix" which is proposed for managing complexity. Characteristics of concerns and their interactions are elaborated. The description of PIROL is completed by a list of integrated tools, initial performance measurements and evaluation. Finally, several concepts relating to the notion of "views" are discussed. Views are a central concern of PIROL. Furthermore, the discussion generalizes over the multi-dimensional presentation in the body of this thesis. Notions, concepts and techniques for views in software engineering are presented and discussed. This discussion connects views in object-oriented databases, aspect-oriented software development and general "concern modeling", to which the method of "Concern Interaction Matrices" contributes. Views are regarded as a central concept of software engineering at the same level as abstraction and decomposition. Dynamic View Connectors are a significant contribution of PIROL that combines database views and aspect-oriented programming. The notion of "views" is defined with far less precision than abstraction and decomposition, but indeed by the overlap and mismatches, which can be captured by views, this concept is a strong principle for structuring software and information. Effort is needed for handling inconsistencies as they may arise, but after all, views are a suitable means for managing the complexity of systems and for designing these systems for evolution

An Empirical Study on the Anticipation of the Result of Copying and Pasting among UML Editors

International audienc

An Empirical Study on the Anticipation of the Result of Copying and Pasting among UML Editors

International audienc

Human-Computer Interaction

In this book the reader will find a collection of 31 papers presenting different facets of Human Computer Interaction, the result of research projects and experiments as well as new approaches to design user interfaces. The book is organized according to the following main topics in a sequential order: new interaction paradigms, multimodality, usability studies on several interaction mechanisms, human factors, universal design and development methodologies and tools

Semantic discovery and reuse of business process patterns

Patterns currently play an important role in modern information systems (IS) development and their use has mainly been restricted to the design and implementation phases of the development lifecycle. Given the increasing significance of business modelling in IS development, patterns have the potential of providing a viable solution for promoting reusability of recurrent generalized models in the very early stages of development. As a statement of research-in-progress this paper focuses on business process patterns and proposes an initial methodological framework for the discovery and reuse of business process patterns within the IS development lifecycle. The framework borrows ideas from the domain engineering literature and proposes the use of semantics to drive both the discovery of patterns as well as their reuse

Proceedings of the 1st International Conference on Live Coding

Open Access peer reviewed papers on live coding published at the 1st International Conference on Live Coding (ICLC) in Leeds

An Effective End-User Development Approach Through Domain-Specific Mashups for Research Impact Evaluation

Over the last decade, there has been growing interest in the assessment of the performance of researchers, research groups, universities and even countries. The assessment of productivity is an instrument to select and promote personnel, assign research grants and measure the results of research projects. One particular assessment approach is bibliometrics i.e., the quantitative analysis of scientific publications through citation and content analysis. However, there is little consensus today on how research evaluation should be performed, and it is commonly acknowledged that the quantitative metrics available today are largely unsatisfactory. A number of different scientific data sources available on the Web (e.g., DBLP, Google Scholar) that are used for such analysis purposes. Taking data from these diverse sources, performing the analysis and visualizing results in different ways is not a trivial and straight forward task. Moreover, people involved in such evaluation processes are not always IT experts and hence not capable to crawl data sources, merge them and compute the needed evaluation procedures. The recent emergence of mashup tools has refueled research on end-user development, i.e., on enabling end-users without programming skills to produce their own applications. We believe that the heart of the problem is that it is impractical to design tools that are generic enough to cover a wide range of application domains, powerful enough to enable the specification of non-trivial logic, and simple enough to be actually accessible to non-programmers. This thesis presents a novel approach for an effective end-user development, specifically for non-programmers. That is, we introduce a domain-specific approach to mashups that "speaks the language of users"., i.e., that is aware of the terminology, concepts, rules, and conventions (the domain) the user is comfortable with.Comment: This PhD dissertation consists of 206 page