Challenges and Directions in Formalizing the Semantics of Modeling Languages

Developing software from models is a growing practice and there exist many model-based tools (e.g., editors, interpreters, debuggers, and simulators) for supporting model-driven engineering. Even though these tools facilitate the automation of software engineering tasks and activities, such tools are typically engineered manually. However, many of these tools have a common semantic foundation centered around an underlying modeling language, which would make it possible to automate their development if the modeling language specification were formalized. Even though there has been much work in formalizing programming languages, with many successful tools constructed using such formalisms, there has been little work in formalizing modeling languages for the purpose of automation. This paper discusses possible semantics-based approaches for the formalization of modeling languages and describes how this formalism may be used to automate the construction of modeling tools

Iterchanging Discrete Event Simulationprocess Interaction Modelsusing The Web Ontology Language - Owl

Discrete event simulation development requires significant investments in time and resources. Descriptions of discrete event simulation models are associated with world views, including the process interaction orientation. Historically, these models have been encoded using high-level programming languages or special purpose, typically vendor-specific, simulation languages. These approaches complicate simulation model reuse and interchange. The current document-centric World Wide Web is evolving into a Semantic Web that communicates information using ontologies. The Web Ontology Language OWL, was used to encode a Process Interaction Modeling Ontology for Discrete Event Simulations (PIMODES). The PIMODES ontology was developed using ontology engineering processes. Software was developed to demonstrate the feasibility of interchanging models from commercial simulation packages using PIMODES as an intermediate representation. The purpose of PIMODES is to provide a vendor-neutral open representation to support model interchange. Model interchange enables reuse and provides an opportunity to improve simulation quality, reduce development costs, and reduce development times

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

Extending Conceptual Schemas with Business Process Information

The specification of business processes is becoming a more and more critical aspect for organizations. Such processes are specified as workflow models expressing the logical precedence among the different business activities (i.e., the units of work). Typically, workflow models are managed through specific subsystems, called workflow management systems, to ensure a consistent behavior of the applications with respect to the organization business process. However, for small organizations and/or simple business processes, the complexity and capabilities of these dedicated workflow engines may be overwhelming. In this paper, we therefore, advocate for a different and lightweight approach, consisting in the integration of the business process specification within the system conceptual schema. We show how a workflow-extended conceptual schema can be automatically obtained, which serves both to enforce the organization business process and to manage all its relevant domain data in a unified way. This extended model can be directly processed with current CASE tools, for instance, to generate an implementation of the system (including its business process) in any technological platform

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

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

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

Artifact-centric business process models in UML : specification and reasoning

Business processes are directly involved in the achievement of an organization's goals, and for this reason they should be performed in the best possible way. Modeling business processes can help to achieve this as, for instance, models can facilitate the communication between the people involved in the process, they provide a basis for process improvement and they can help perform process management. Processes can be modeled from many different perspectives. Traditional process modeling has followed the process-centric (or activity-centric) perspective, where the focus is on the sequencing of activities (i.e. the control flow), largely ignoring or underspecifying the data required by these tasks. In contrast, the artifact-centric (or data-centric) approach to process modeling focuses on defining the data required by the tasks and the details of the tasks themselves in terms of the changes they make to the data. The BALSA framework defines four dimensions which should be represented in any artifact-centric business process model: business artifacts, lifecycle, services (i.e. tasks) and associations. Using different types of models to represent these dimensions will result in distinct representations, whose differing characteristics (e.g. the degree of formality or understandability) will make them more appropriate for one purpose or another. Considering this, in the first part of this thesis we propose a framework, BAUML, for modeling business processes following an artifact-centric perspective. This framework is based on using a combination of UML and OCL models, and its goal is to have a final representation of the process which is both understandable and formal, to avoid ambiguities and errors. However, once a process model has been defined, it is important to ensure its quality. This will avoid the propagation of errors to the process's implementation. Although there are many different quality criteria, we focus on the semantic correctness of the model, answering questions such as "does it represent reality correctly?" or "are there any errors and contradictions in it?". Therefore, the second part of this thesis is concerned with finding a way to determine the semantic correctness of our BAUML models. We are interested in considering the BAUML model as a whole, including the meaning of the tasks. To do so, we first translate our models into a well-known framework, a DCDS (Data-centric Dynamic System) to which then modelchecking techniques can be applied. However, DCDSs have been defined theoretically and there is no tool that implements them. For this reason, we also created a prototype tool, AuRUS-BAUML, which is able to translate our BAUML models into logic and to reason on their semantic correctness using an existing tool, SVTe. The integration between AuRUS-BAUML and SVTe is transparent to the user. Logically, the thesis also presents the logic translation which is performed by the tool.Els processos de negoci estan directament relacionats amb els objectius de negoci, i per tant és important que aquests processos es duguin a terme de la millor manera possible. Optar per modelar-los pot ajudar a aconseguir-ho, ja que els models proporcionen nombrosos avantatges. Per exemple: faciliten la comunicació entre les parts involucrades en el procés, proporcionen una base a partir del qual millorar-lo, i poden ajudar a gestionar-lo. Els processos es poden modelar des de diferents perspectives. El modelat tradicional de processos s'ha basat molt en la perspectiva anomenada "process-centric" (centrada en processos) o "activity-centric" (centrada en activitats), que posa l'èmfasi en la seqüència d'activitats o tasques que s'han d'executar, ignorant en gran mesura les dades necessàries per dur a terme aquestes tasques. Per altra banda, la perspectiva "artifact-centric" (centrada en artefactes) o "data-centric" es basa en definir les dades que necessiten les tasques i els detalls de les tasques en si, representant els canvis que aquestes fan a les dades. El framework BALSA defineix quatre dimensions que haurien de representar-se en qualsevol model artifact-centric: els artefactes de negoci (business artifacts), els cicles de vida (lifecycles), els serveis (services) i les associacions (associations). Utilitzant diferents tipus de models per representar aquestes dimensions porta a obtenir diverses representacions amb característiques diferents. Aquesta varietat de característiques farà que els models resultants siguin més apropiats per un propòsit o per un altre. Considerant això, en la primera part d'aquesta tesi proposem un framework, BAUML, per modelar processos de negoci seguint una perspectiva artifact-centric. El framework es basa en utilitzar una combinació de models UML i OCL, i el seu objectiu és obtenir una representació final del procés que sigui a la vegada comprensible i formal, per tal d'evitar ambigüitats i errors. Un cop definit el procés, és important assegurar-ne la qualitat. Això evitarà la propagació d'errors a la implementació final del procés. Malgrat que hi ha molts criteris de qualitat diferents, ens centrarem en la correctesa semàntica del model, per respondre a preguntes com ara "representa la realitat correctament?" o "conté errors o contradiccions?". En conseqüència, la segona part d'aquesta tesi se centra en buscar una manera per determinar la correctesa semàntica d'un model BAUML. Ens interessa considerar el model com un tot, incloent el significat de les tasques (és a dir, el detall del que fan). Per aconseguir-ho, primer traduïm les tasques a un framework reconegut, DCDSs (Data-centric Dynamic Systems). Un cop obtingut, s'hi poden aplicar tècniques de model-checking per determinar si compleix certes propietats. Malauradament, els DCDSs s'han definit a nivell teòric i no hi ha cap eina que els implementi. Per aquest motiu, hem creat un prototip d'eina, AuRUS-BAUML, que és capaç de traduir els nostres models BAUML a lògica i aplicar-hi tècniques de raonament per determinar-ne la correctesa semàntica. Per la part de raonament, l'AuRUS-BAUML fa servir una eina existent, l'SVTe. La integració entre l'AuRUS-BAUML i l'SVTe és transparent de cara a l'usuari. Lògicament, la tesi també presenta la traducció a lògica que porta a terme l'eina

A System for Deduction-based Formal Verification of Workflow-oriented Software Models

The work concerns formal verification of workflow-oriented software models using deductive approach. The formal correctness of a model's behaviour is considered. Manually building logical specifications, which are considered as a set of temporal logic formulas, seems to be the significant obstacle for an inexperienced user when applying the deductive approach. A system, and its architecture, for the deduction-based verification of workflow-oriented models is proposed. The process of inference is based on the semantic tableaux method which has some advantages when compared to traditional deduction strategies. The algorithm for an automatic generation of logical specifications is proposed. The generation procedure is based on the predefined workflow patterns for BPMN, which is a standard and dominant notation for the modeling of business processes. The main idea for the approach is to consider patterns, defined in terms of temporal logic,as a kind of (logical) primitives which enable the transformation of models to temporal logic formulas constituting a logical specification. Automation of the generation process is crucial for bridging the gap between intuitiveness of the deductive reasoning and the difficulty of its practical application in the case when logical specifications are built manually. This approach has gone some way towards supporting, hopefully enhancing our understanding of, the deduction-based formal verification of workflow-oriented models.Comment: International Journal of Applied Mathematics and Computer Scienc