Reactive Rules for Emergency Management

The goal of the following survey on Event-Condition-Action (ECA) Rules is to come to a common understanding and intuition on this topic within EMILI. Thus it does not give an academic overview on Event-Condition-Action Rules which would be valuable for computer scientists only. Instead the survey tries to introduce Event-Condition-Action Rules and their use for emergency management based on real-life examples from the use-cases identified in Deliverable 3.1. In this way we hope to address both, computer scientists and security experts, by showing how the Event-Condition-Action Rule technology can help to solve security issues in emergency management. The survey incorporates information from other work packages, particularly from Deliverable D3.1 and its Annexes, D4.1, D2.1 and D6.2 wherever possible

Designing Traceability into Big Data Systems

Providing an appropriate level of accessibility and traceability to data or process elements (so-called Items) in large volumes of data, often Cloud-resident, is an essential requirement in the Big Data era. Enterprise-wide data systems need to be designed from the outset to support usage of such Items across the spectrum of business use rather than from any specific application view. The design philosophy advocated in this paper is to drive the design process using a so-called description-driven approach which enriches models with meta-data and description and focuses the design process on Item re-use, thereby promoting traceability. Details are given of the description-driven design of big data systems at CERN, in health informatics and in business process management. Evidence is presented that the approach leads to design simplicity and consequent ease of management thanks to loose typing and the adoption of a unified approach to Item management and usage.Comment: 10 pages; 6 figures in Proceedings of the 5th Annual International Conference on ICT: Big Data, Cloud and Security (ICT-BDCS 2015), Singapore July 2015. arXiv admin note: text overlap with arXiv:1402.5764, arXiv:1402.575

Designing Reusable Systems that Can Handle Change - Description-Driven Systems : Revisiting Object-Oriented Principles

In the age of the Cloud and so-called Big Data systems must be increasingly flexible, reconfigurable and adaptable to change in addition to being developed rapidly. As a consequence, designing systems to cater for evolution is becoming critical to their success. To be able to cope with change, systems must have the capability of reuse and the ability to adapt as and when necessary to changes in requirements. Allowing systems to be self-describing is one way to facilitate this. To address the issues of reuse in designing evolvable systems, this paper proposes a so-called description-driven approach to systems design. This approach enables new versions of data structures and processes to be created alongside the old, thereby providing a history of changes to the underlying data models and enabling the capture of provenance data. The efficacy of the description-driven approach is exemplified by the CRISTAL project. CRISTAL is based on description-driven design principles; it uses versions of stored descriptions to define various versions of data which can be stored in diverse forms. This paper discusses the need for capturing holistic system description when modelling large-scale distributed systems.Comment: 8 pages, 1 figure and 1 table. Accepted by the 9th Int Conf on the Evaluation of Novel Approaches to Software Engineering (ENASE'14). Lisbon, Portugal. April 201

Semantics and Verification of UML Activity Diagrams for Workflow Modelling

This thesis defines a formal semantics for UML activity diagrams that is suitable for workflow modelling. The semantics allows verification of functional requirements using model checking. Since a workflow specification prescribes how a workflow system behaves, the semantics is defined and motivated in terms of workflow systems. As workflow systems are reactive and coordinate activities, the defined semantics reflects these aspects. In fact, two formal semantics are defined, which are completely different. Both semantics are defined directly in terms of activity diagrams and not by a mapping of activity diagrams to some existing formal notation. The requirements-level semantics, based on the Statemate semantics of statecharts, assumes that workflow systems are infinitely fast w.r.t. their environment and react immediately to input events (this assumption is called the perfect synchrony hypothesis). The implementation-level semantics, based on the UML semantics of statecharts, does not make this assumption. Due to the perfect synchrony hypothesis, the requirements-level semantics is unrealistic, but easy to use for verification. On the other hand, the implementation-level semantics is realistic, but difficult to use for verification. A class of activity diagrams and a class of functional requirements is identified for which the outcome of the verification does not depend upon the particular semantics being used, i.e., both semantics give the same result. For such activity diagrams and such functional requirements, the requirements-level semantics is as realistic as the implementation-level semantics, even though the requirements-level semantics makes the perfect synchrony hypothesis. The requirements-level semantics has been implemented in a verification tool. The tool interfaces with a model checker by translating an activity diagram into an input for a model checker according to the requirements-level semantics. The model checker checks the desired functional requirement against the input model. If the model checker returns a counterexample, the tool translates this counterexample back into the activity diagram by highlighting a path corresponding to the counterexample. The tool supports verification of workflow models that have event-driven behaviour, data, real time, and loops. Only model checkers supporting strong fairness model checking turn out to be useful. The feasibility of the approach is demonstrated by using the tool to verify some real-life workflow models

Continuous Workflows: From Model to Enactment System

Workflows are actively being used in both business and scientific domains to automate processes and facilitate collaboration. A workflow management (or enactment) system (WfMS) defines, creates and manages the execution of workflows on one or more workflow engines, which are able to interpret workflow definitions, allocate resources, interact with workflow participants and, where required, invoke the needed tools (e.g., databases, job schedulers, etc.) and applications. Traditional WfMSs and workflow design processes view the workflow as a one-time interaction with the various data sources, i.e., when a workflow is invoked, its steps are executed once and in-order. The fundamental underlying assumption has been that data sources are passive and all interactions are structured along the request/reply (query) model. Hence, traditional WfMS cannot effectively support business or scientific monitoring applications that require the processing of data streams such as those generated by sensing devices as well as mobile and web applications. It is the hypothesis of this dissertation that Workflow Management Systems can be extended to support data stream semantics to enable monitoring applications. This includes the ability to apply flexible bounds on unbounded data streams and the ability to facilitate on-the-fly processing of bounded bundles of data (window semantics). To support this hypothesis this dissertation has produced new specifications, a design, an implementation and a thorough evaluation of a novel Continuous Workflows (CWf) model, which is backwards compatible with currently available workflow models. The CWf model was implemented in a CONtinuous workFLow ExeCution Engine, CONFLuEnCE, as an extension of Kepler, which is a popular scientific WfMS. The applicability of the CWf model in both scientific and business applications was demonstrated by utilizing CONFLuEnCE in Astroshelf to support live annotations (i.e., monitoring of astronomical data), and to support supply chain monitoring and management. The implementation of CONFLuEnCE led to the realization that different applications have different performance requirements and hence an integrated workflow scheduling framework is essential. Towards meeting this need, STAFiLOS, a Stream FLOw Scheduling framework for Continuous Workflows, was designed and implemented, within CONFLuEnCE. The performance of STAFiLOS was evaluated using the Linear Road Benchmark for continuous workflows

Live Graph Databases Using DCR Graphs

Nowadays, it is of uttermost importance for companies that want to be relevant on the market to produce more while making fewer mistakes. Good management practices recommend the replication of critical business operations, like hiring a new employee and the set up he has to go through to have the company tools available, or the steps and decisions required when producing some daily report. The possibility of creating and refining these processes through business process systems to better suit the daily activity of an enterprise has a direct impact on the overall productivity, organization, and cost-reduction. The commonly used process systems make use of notations that are like state machines, having a somewhat imperative style depicting a narrow path where every decision in a process is sequential – providing the user no chance to offer input on how the process carries out – and struggle to take data into account. The proposal of several declarative languages and notations meant to solve this problem, easily incorporating data alongside the specified workflow, and providing actual control to the end-user on how the processes are accomplished by stating what can/needs to be done rather than how to do it in a step-by-step fashion. With this dissertation we present ReDa, a novel declarative, dynamic, and reactive data-centric process language, and the mapping from its specification to a running system (the operational semantics) implemented using the mechanisms of a graph-database, namely neo4j. We also present and evaluate a prototype of a business process system able to emulate the process via a reactive application, addressing the challenges of having a system that interacts with a dynamic process, and the solutions adopted.Atualmente, para que uma empresa possa ser relevante no mercado é bastante importante que a sua produção aumente e que a sua taxa de erros diminua. Regras de boa prática no que toca ao controlo de processos de uma empresa recomendam que as suas tarefas mais críticas sejam efetuadas da mesma forma independentemente de quem as executa, tal como a contratação de um novo empregado e todos os passos que ele precisa de executar para que reúna as condições necessárias para trabalhar, ou quais os pontos-chave obrigatórios a seguir quando se submetem relatórios. A possibilidade de criar e ajustar estes processos ao dia a dia de uma empresa tem um impacto direto na sua produtividade, organização e redução de custos. Os sistemas de processos mais utilizados adotam notações semelhantes a máquinas de estado, onde definem as suas atividades de uma forma sequencial e têm dificuldade em incorporar dados no processo. A proposta de várias linguagens de processos declarativas tem como objetivo solucionar este problema, permitindo a definição do processo e dos seus dados de forma simultânea e flexível, pois ao invés de se definir uma sequência de execução é possível estabelecer o que pode/tem de ser feito. Com esta dissertação apresentamos a ReDa, uma nova linguagem declarativa, dinâmica e reativa centrada em dados, e um mapeamento desta especificação para um sistema de execução que utiliza os mecanismos de uma base de dados de grafos, nomeadamente o neo4j. Apresentamos e avaliamos também um protótipo de sistema de gestão de processos capaz de emular processos ReDa através de uma aplicação reativa, abordando os desafios de desenvolver um sistema que interaja com um processo dinâmico e as soluções adotadas

Comparing Petri Net and Activity Diagram Variants for Workflow Modelling:A Quest for Reactive Petri Nets

Petri net variants are widely used as a workflow modelling technique. Recently, UMLa ctivity diagrams have been used for the same purpose, even though the syntax and semantics of activity diagrams has not been yet fully worked out. Nevertheless, activity diagrams seem very similar to Petri nets and on the surface, one may think that they are variants of each other. To substantiate or deny this claim, we need to formalise the intended semantics of activity diagrams and then compare this with various Petri net semantics. In previous papers we have defined two formal semantics for UMLact ivity diagrams that are intended for workflow modelling. In this paper, we discuss the design choices that underlie these two semantics and investigate whether these design choices can be met in low-level and high-level Petri net semantics. We argue that the main difference between the Petri net semantics and our semantics of UML act ivity diagrams is that the Petri net semantics models resource usage of closed, active systems that are non-reactive, whereas our semantics of UMLact ivity diagrams models open, reactive systems. Since workflow systems are open, reactive systems, we conclude that Petri nets cannot model workflows accurately, unless they are extended with a syntax and semantics for reactivity