Modelling Requirements for Content Recommendation Systems

This paper addresses the modelling of requirements for a content Recommendation System (RS) for Online Social Networks (OSNs). On OSNs, a user switches roles constantly between content generator and content receiver. The goals and softgoals are different when the user is generating a post, as opposed as replying to a post. In other words, the user is generating instances of different entities, depending on the role she has: a generator generates instances of a "post", while the receiver generates instances of a "reply". Therefore, we believe that when addressing Requirements Engineering (RE) for RS, it is necessary to distinguish these roles clearly. We aim to model an essential dynamic on OSN, namely that when a user creates (posts) content, other users can ignore that content, or themselves start generating new content in reply, or react to the initial posting. This dynamic is key to designing OSNs, because it influences how active users are, and how attractive the OSN is for existing, and to new users. We apply a well-known Goal Oriented RE (GORE) technique, namely i-star, and show that this language fails to capture this dynamic, and thus cannot be used alone to model the problem domain. Hence, in order to represent this dynamic, its relationships to other OSNs' requirements, and to capture all relevant information, we suggest using another modelling language, namely Petri Nets, on top of i-star for the modelling of the problem domain. We use Petri Nets because it is a tool that is used to simulate the dynamic and concurrent activities of a system and can be used by both practitioners and theoreticians.Comment: 28 pages, 7 figure

Supporting user-oriented analysis for multi-view domain-specific visual languages

This is the post-print version of the final paper published in Information and Software Technology. The published article is available from the link below. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. Copyright @ 2008 Elsevier B.V.The integration of usable and flexible analysis support in modelling environments is a key success factor in Model-Driven Development. In this paradigm, models are the core asset from which code is automatically generated, and thus ensuring model correctness is a fundamental quality control activity. For this purpose, a common approach is to transform the system models into formal semantic domains for verification. However, if the analysis results are not shown in a proper way to the end-user (e.g. in terms of the original language) they may become useless. In this paper we present a novel DSVL called BaVeL that facilitates the flexible annotation of verification results obtained in semantic domains to different formats, including the context of the original language. BaVeL is used in combination with a consistency framework, providing support for all steps in a verification process: acquisition of additional input data, transformation of the system models into semantic domains, verification, and flexible annotation of analysis results. The approach has been validated analytically by the cognitive dimensions framework, and empirically by its implementation and application to several DSVLs. Here we present a case study of a notation in the area of Digital Libraries, where the analysis is performed by transformations into Petri nets and a process algebra.Spanish Ministry of Education and Science and MODUWEB

Overview on agent-based social modelling and the use of formal languages

Transdisciplinary Models and Applications investigates a variety of programming languages used in validating and verifying models in order to assist in their eventual implementation. This book will explore different methods of evaluating and formalizing simulation models, enabling computer and industrial engineers, mathematicians, and students working with computer simulations to thoroughly understand the progression from simulation to product, improving the overall effectiveness of modeling systems.Postprint (author's final draft

Presenting Business Process Improvement Changes – A Systematic Literature Review

Äriprotsessi täiustamine aitab parandada lõppkasutaja kogemust, vähendada kulutusi ja kiirendada tööd. Eksisteerib mitmeid äriprotsessi täiustamise tehnikaid. Olemasolevate protsesside juures ei ole aga demonstreeritud muutuste mõju. Et täita see lünk, pakub antud lõputöö ülevaadet viisidest, kuidas demonstreerida äriprotsesside muutuste mõju päris elu näidete põhjal. Sel eesmärgil on tehtud süstemaatiline kirjanduse ülevaade artiklitest, mis kasutavad äriprotsesside täiustamist päris elu näidetes, et näha, kuidas need muutuseid on esitletud. Leitud artikleid analüüsiti ning leiti vastused uurimuse küsimustele. Analüüsi tulemusena leiti, et nagu igas teises teadusvaldkonnas, mis käsitleb muutusi, saab neid esitleda visuaalselt, numbriliselt või mitte- struktureeritud viisil, kasutates erinevaid esitlemise strateegiaid. Teadmine, kuidas antakse edasi asjade muutumist, aitab inimestel paremini aru saada nende sisust. Võimalik on paremini aru saada äriprotsesside muutustest.Business Process Improvement (BPI) has a big potential by helping to improve end-user satisfaction, to reduce costs and throughput times. A lot of business process improvement techniques exist, but they lack the information about the presentation of the effects of business process change. In order to fill this gap, this thesis provides an overview of the ways that are used to present the effects of business process change in real-life business process scenarios. For that purpose, a systematic literature review is performed to identify papers that apply BPI on real-life cases from industry to see what means are used to capture and present those changes. The identified final papers are analysed in order to answer to Research Questions (RQ). The analysis reveals that as in any other scientific field where change is occurring the change could be presented either visually, or in a numerical way, or in a not structured (narrative) way using some presentation strategies. This knowledge that gives some hints on how changes are conveyed can be used to support people to better understand the changes which occur in a process after a BPI

Modelica - A Language for Physical System Modeling, Visualization and Interaction

Modelica is an object-oriented language for modeling of large, complex and heterogeneous physical systems. It is suited for multi-domain modeling, for example for modeling of mechatronics including cars, aircrafts and industrial robots which typically consist of mechanical, electrical and hydraulic subsystems as well as control systems. General equations are used for modeling of the physical phenomena, No particular variable needs to be solved for manually. A Modelica tool will have enough information to do that automatically. The language has been designed to allow tools to generate efficient code automatically. The modeling effort is thus reduced considerably since model components can be reused and tedious and error-prone manual manipulations are not needed. The principles of object-oriented modeling and the details of the Modelica language as well as several examples are presented

ARCHITECTURE-BASED RELIABILITY ANALYSIS OF WEB SERVICES

In a Service Oriented Architecture (SOA), the hierarchical complexity of Web Services (WS) and their interactions with the underlying Application Server (AS) create new challenges in providing a realistic estimate of WS performance and reliability. The current approaches often treat the entire WS environment as a black-box. Thus, the sensitivity of the overall reliability and performance to the behavior of the underlying WS architectures and AS components are not well-understood. In other words, the current research on the architecture-based analysis of WSs is limited. This dissertation presents a novel methodology for modeling the reliability and performance of web services. WSs are treated as atomic entities but the AS is broken down into layers. More specifically, interactions of WSs with the underlying layers of an AS are investigated. One important feature of the research is investigating the impact of dynamic parameters that exist at the layers, such as configuration parameters. These parameters may have negative impact on WSs performance if they are not configured properly. WSs are developed in house and the AS considered is JBoss AS. An experimental environment is setup so that controlled service requests can be generated and important performance metrics can be recorded under various configurations of the AS. On the other hand, a simulation model is developed from the source code and run-time behavior of the existing WS and AS implementations. The model mimics the logical behavior of the WSs based on their communication with the AS layers. The simulation results are compared to the experimental results to ensure the correctness of the model. The architecture of the simulation model, which is based on Stochastic Petri Nets (SPN), is modularized in accordance to the layers and their interactions. As the web services are often executed in a complex and distributed environment, the modularized approach enables a user or a designer to observe and investigate the performance of the entire system under various conditions. In contrast, most approaches to WSs analyses are monolithic in that the entire system is treated as a closed box. The results show that 1) the simulation model can be a viable tool for measuring the performance and reliability of WSs under different loads and conditions that may be of great interest to WS designers and the professionals involved; 2) Configuration parameters have big impacts on the overall performance; 3) The simulation model can be tuned to account for various speeds in terms of communication, hardware, and software; 4) As the simulation model is modularized, it may be used as a foundation for aggregating the modules (layers), nullifying modules, or the model can be enhanced to include other aspects of the WS architecture such as network characteristics and the hardware/operating system on which the AS and WSs execute; and 5) The simulation model is beneficial to predict the performance of web services for those cases that are difficult to replicate in a field study

Analysable software language translations

Dissertação para obtenção do Grau de Doutor em Engenharia InformáticaThe most difficult tasks in the Software Language Engineering (SLE) process, are the design of the semantics of a Domain Specific Modeling Language (DSML), its implementation (typically in a form of a compiler), and also its verification and validation. On the one hand, the choice of the appropriate level of abstraction when designing a DSML’s semantics, affects directly its usability, and the potential for its analysis. On the other hand, in practice, not only the compiler’s implementation, but also its verification and validation are performed manually, while having as reference the DSML’s semantic models. The challenge of this research work is to apply a complete model driven software development approach in the tasks of designing a DSML’s semantics, implementing, verifying and validating DSMLs’ compilers. This involves the choice of the most appropriate abstraction levels, and the design and development of adequate tools to support SLE practitioners on these tasks. This thesis reports: i) the design and implementation of formal languages (and associated tools) to support the task of DSML’s semantics design (i.e., DSLTrans and SOS); ii) the automatic generation of DSMLs’ compilers based on translation specifications; and iii) automated validation of DSMLs’ semantic designs based on the analysis of translation specifications. Finally, the approach presented in this thesis is illustrated with the design and implementation of a real life DSML