Toward the use of Petri nets for the formalization of OWL-S choreographies

In this paper, we present a Petri net-based approach for modeling the choreography of semantic Web services which are described following the OWL-S specification. In our approach, each control construct of the OWL-S choreography is represented through a Petri net pattern that captures formally its operational semantics. The main difference between our work and the main proposals that model the semantics of OWL-S services choreography is that, although both approaches represent the service choreography with Petri nets, our proposal is also concerned with the practical execution of the Petri nets by the client. Therefore we also represent the flow of data, the outputs transformations, the effects in the environment, in addition to the structures that control the choreography of the services in our Petri net models. The implementation of the OWL-S choreography is performed in a Petri net ontology-based engine. This is another difference with traditional approaches that only use Petri nets for the analysis of the service properties. Furthermore, the use of an underlying ontology engine for supporting both the domain models of OWL-S services and the Petri net models provides several advantages in terms of reasoning, extension, and reuse.     

BPMNt: A BPMN extension for specifying software process tailoring

ContextAlthough SPEM 2.0 has great potential for software process modeling, it does not provide concepts or formalisms for precise modeling of process behavior. Indeed, SPEM fails to address process simulation, execution, monitoring and analysis, which are important activities in process management. On the other hand, BPMN 2.0 is a widely used notation to model business processes that has associated tools and techniques to facilitate the aforementioned process management activities. Using BPMN to model software development processes can leverage BPMN’s infrastructure to improve the quality of these processes. However, BPMN lacks an important feature to model software processes: a mechanism to represent process tailoring.ObjectiveThis paper proposes BPMNt, a conservative extension to BPMN that aims at creating a tailoring representation mechanism similar to the one found in SPEM 2.0.MethodWe have used the BPMN 2.0 extensibility mechanism to include the representation of specific tailoring relationships namely suppression, local contribution, and local replacement, which establish links between process elements (such as in the case of SPEM). Moreover, this paper also presents some rules to ensure the consistency of BPMN models when using tailoring relationships.ResultsIn order to evaluate our proposal we have implemented a tool to support the BPMNt approach and have applied it for representing real process adaptations in the context of an academic management system development project. Results of this study showed that the approach and its support tool can successfully be used to adapt BPMN-based software processes in real scenarios.ConclusionWe have proposed an approach to enable reuse and adaptation of BPMN-based software process models as well as derivation traceability between models through tailoring relationships. We believe that bringing such capabilities into BPMN will open new perspectives to software process management.     

Recommendation-based editor for business process modeling

To ensure proper and efficient modeling of business processes, it is important to support users of process editors adequately. With only minimal modeling support, the productivity of novice business process modelers may be low when starting process modeling. In this article, we present a theoretically sound and empirically validated recommendation-based modeling support system, which covers different aspects of business process modeling. We consider basic functionality, such as an intuitive search interface, as well as advanced concepts like patterns observed in other users' preferences. Additionally, we propose a multitude of interaction possibilities with the recommendation system, e.g., different metrics that can be used in isolation or an overall recommender component that combines several sub metrics into one comprehensive score. We validate a prototype implementation of the recommendation system with exhaustive user experiments based on real-life process models. To our knowledge, this is the only comprehensive recommendation system for business process modeling that is available.     

Modeling process-related RBAC models with extended UML activity models

Context

Business processes are an important source for the engineering of customized software systems and are constantly gaining attention in the area of software engineering as well as in the area of information and system security. While the need to integrate processes and role-based access control (RBAC) models has been repeatedly identified in research and practice, standard process modeling languages do not provide corresponding language elements.

Objective

In this paper, we are concerned with the definition of an integrated approach for modeling processes and process-related RBAC models - including roles, role hierarchies, statically and dynamically mutual exclusive tasks, as well as binding of duty constraints on tasks.

Method

We specify a formal metamodel for process-related RBAC models. Based on this formal model, we define a domain-specific extension for a standard modeling language.

Results

Our formal metamodel is generic and can be used to extend arbitrary process modeling languages. To demonstrate our approach, we present a corresponding extension for UML2 activity models. The name of our extension is Business Activities. Moreover, we implemented a library and runtime engine that can manage Business Activity runtime models and enforce the different policies and constraints in a software system.

Conclusion

The definition of process-related RBAC models at the modeling-level is an important prerequisite for the thorough implementation and enforcement of corresponding policies and constraints in a software system. We identified the need for modeling support of process-related RBAC models from our experience in real-world role engineering projects and case studies. The Business Activities approach presented in this paper is successfully applied in role engineering projects.     

Interaction-centric modeling of process choreographies

With the rise of electronic integration between organizations, the need for a precise specification of interaction behavior increases. Information systems, replacing interaction previously carried out by humans via phone, faxes and emails, require a precise specification for handling all possible situations. Such interaction behavior is described in process choreographies. While many proposals for choreography languages have already been made, most of them fall into the category of interconnection models, where the observable behavior of the different partners is described and then related via message flow. As this article will show, this modeling approach fails to support fundamental design principles of choreographies and typically leads to modeling errors. This motivates an alternative modeling style, namely interaction modeling, for overcoming these limitations. While the main concepts are independent of a concrete modeling language, iBPMN is introduced as novel interaction modeling language. Formal execution semantics are provided and a comprehensive toolset implementing the approach is presented.     

Interacting services: From specification to execution

Interacting services play a key role to realize business process integration among different business partners by means of electronic message exchange. In order to provide seamless integration of these services, the messages exchanged as well as their dependencies must be well-defined. Service choreographies are a means to describe the allowed conversations. This article presents a requirements framework for service choreography languages, along which existing choreography languages are assessed. The requirements framework provides the basis for introducing the language BPEL4Chor, which extends the industry standard WS-BPEL with choreography-specific concepts. A validation is provided and integration with executable service orchestrations is discussed.     

A formal and visual modeling approach to choreography based web services composition and conformance verification

Web services have emerged as the building blocks of a service-oriented architecture that supports not only enterprise application integration (EAI) and business process management (BPM) within an organization but also B2B collaboration based on business process integration. The web services choreography approach to B2B process integration allows business partners to orchestrate their own web services privately, while conforming with an agreed specification of the common ordering conditions and constraints under which messages are exchanged among partners’ web services. In this approach, choreography conformance is an essential requirement for the successful implementation of collaborative processes. A formal approach to web services composition and conformance verification based on WS-CDL and WS-BPEL is presented. This approach involves model checking as an automated means of verifying choreography conformance. The main contributions include a precise notion of choreography conformance on which verification is based as well as support for the complementary use of visual modeling (e.g. UML) and standard WS-¹ notations in composition.     

Process-mining enabled feedback: “Tell me what I did wrong” vs. “tell me how to do it right”

Fast advancement of technology has led to an increased interest for using information technology to provide feedback based on learning behavior observations. This work outlines a novel approach for analyzing behavioral learner data through the application of process mining techniques specifically targeting a complex problem solving process. We realize this in the context of one particular learning case, namely, domain modeling. This work extends our previous research on process-mining analysis of domain modeling behavior of novices by elaborating with new insights from a replication study enhanced with an extra observation on how novices verify/validate models. The findings include a set of typical modeling and validation patterns that can be used to improve teaching guidance for domain modeling courses. From a scientific viewpoint, the results contribute to improving our knowledge on the cognitive aspects of problem-solving behavior of novices in the area of domain modeling, specifically regarding process-oriented feedback as opposed to traditional outcome feedback (is a solution correct? Why (not)?) usually applied in this type of courses. Ultimately, the outcomes of the work can be inspirational outside of the area of domain modeling as learning event data is becoming readily available through virtual learning environments and other information systems.     

Using intentional fragments to bridge the gap between organizational and intentional levels

ContextBusiness process models provide a natural way to describe real-world processes to be supported by software-intensive systems. These models can be used to analyze processes in the system-as-is and describe potential improvements for the system-to-be. But, how well does a given business process model satisfy its business goals? How can different perspectives be integrated in order to describe an inter-organizational process?ObjectiveThe aim of the present paper is to link the local and the global perspectives of the inter-organizational business process defined in BPMN 2.0 (Business Process Model and Notation) to KAOS goal models (Keep All Objectives Satisfied). We maintain a separation of concerns between the intentional level captured by the goal model and the organizational level captured by the process model. The paper presents the concept of intentional fragment (a set of flow elements of the process with a common purpose) and assess its usefulness.MethodWe conducted empirical experiments where the proposed concepts – here the intentional fragments – are validated by users. Our method relies on an iterative improvement process led by users feedback.ResultsWe find that the concept of intentional fragment is useful for (1) analyzing the business process model (2) reasoning about the relations between the goal model and the business process model and (3) identifying new goals. In a previous work we focused on BPMN 2.0 collaboration models (local view). This paper extends the previous work by integrating the global view given by choreography models in the approach.ConclusionWe conclude that the notion of intentional fragment is a useful mean to relate business process models and goal models while dealing with their different nature (activity oriented vs goal oriented). Intentional fragments can also be used to analyze the process model and to infer new goals in an iterative manner.     

A centralized and a decentralized method to automatically derive choreography-conforming web service systems

We present a formal model to represent orchestrations and choreographies and we define several conformance semantic relations allowing to detect whether a set of orchestration models, representing some web services, leads to the overall communications described in a choreography. Given this formal model, we develop automatic methods to derive a set of web services from a given choreography, in such a way that the system consisting of these services necessarily conforms to the choreography. These methods enable the construction of conforming systems of services even in cases where projecting the choreography into each service would lead to a non-conforming system. This issue is addressed by adding some control messages that make services interact as required by the choreography. Two different derivation methods are presented. In the centralized method, a new service is responsible of managing these additional control messages. In the decentralized method, the responsibility of handling these messages is distributed among all services.     

From fine-grained to abstract process models: A semantic approach

Organizations actively managing their business processes face a rapid growth of the number of process models that they maintain. Business process model abstraction has proven to be an effective means to generate readable, high-level views on business process models by showing coarse-grained activities and leaving out irrelevant details. In this way, abstraction facilitates a more efficient management of process models, as a single model can provide for many relevant views. Yet, it is an open question how to perform abstraction in the same skillful way as experienced modelers combine activities into more abstract tasks. This paper presents an approach that uses semantic information of a process model to decide on which activities belong together, which extends beyond existing approaches that merely exploit model structural characteristics. The contribution of this paper is twofold: we propose a novel activity aggregation method and suggest how to discover the activity aggregation habits of human modelers. In an experimental validation, we use an industrial process model repository to compare the developed activity aggregation method with actual modeling decisions, and observe a strong correlation between the two. The presented work is expected to contribute to the development of modeling support for the effective process model abstraction.     

Topologically correct reconstruction of tortuous contour forests

Motivated by the need for correct and robust 3D models of neuronal processes, we present a method for reconstruction of spatially realistic and topologically correct models from planar cross sections of multiple objects. Previous work in 3D reconstruction from serial contours has focused on reconstructing one object at a time, potentially producing inter-object intersections between slices. We have developed a robust algorithm that removes these intersections using a geometric approach. Our method not only removes intersections but can guarantee a given minimum separation distance between objects. This paper describes the algorithm for geometric adjustment, proves correctness, and presents several results of our high-fidelity modeling.     

Synthesizing interpreted domain-specific models to manage smart microgrids

The increase in prominence of model-driven software development (MDSD) has placed emphasis on the use of domain-specific modeling languages (DSMLs) during the development process. DSMLs allow for domain concepts to be conceptualized and represented at a high level of abstraction. Currently, most DSML models are converted into high-level languages (HLLs) through a series of model-to-model and/or model-to-text transformations before they are executed. An alternative approach for model execution is the interpretation of models directly without converting them into an HLL. These models are created using interpreted DSMLs (i-DSMLs) and realized using a semantic-rich execution engine or domain-specific virtual machine (DSVM).In this article we present an approach for model synthesis, the first stage of model interpretation, that separates the domain-specific knowledge (DSK) from the model of execution (MoE). Previous work on model synthesis tightly couples the DSK and MoE reducing the ability for implementations of the DSVM to be easily reused in other domains. To illustrate how our approach to model synthesis works for i-DSMLs, we have created MGridML, an i-DSML for energy management in smart microgrids, and an MGridVM prototype, the DSVM for MGridML. We evaluated our approach by performing experiments on the model synthesis aspect of MGridVM and comparing the results to a DSVM from the user-centric communication domain.     

Event based choreography

An important feature of the service-oriented approach is the ability to aggregate, through programmable coordination patterns, the activities involved in service interactions. Two different approaches can be adopted to tackle service coordination: orchestration and choreography. In this paper, we introduce a formal methodology to handle coordination among services from the perspective of a global observer, in the spirit of choreography models. In particular, we address the problem of verifying compliance and consistency between the design of service interactions and the choreography constraints.     

Deep recurrent Gaussian processes for outlier-robust system identification

Gaussian Processes (GP) comprise a powerful kernel-based machine learning paradigm which has recently attracted the attention of the nonlinear system identification community, specially due to its inherent Bayesian-style treatment of the uncertainty. However, since standard GP models assume a Gaussian distribution for the observation noise, i.e., a Gaussian likelihood, the learning and predictive capabilities of such models can be severely degraded when outliers are present in the data. In this paper, motivated by our previous work on GP learning with data containing outliers and recent advances in hierarchical (deep GPs) and recurrent GP (RGP) approaches, we introduce an outlier-robust recurrent GP model, the RGP-t. Our approach explicitly models the observation layer, which includes a heavy-tailed Student-t likelihood, and allows for a hierarchy of multiple transition layers to learn the system dynamics directly from estimation data contaminated by outliers. In addition, we modify the original variational framework of standard RGP in order to perform inference with the new RGP-t model. The proposed approach is comprehensively evaluated using six artificial benchmarks, within several outlier contamination levels, and two datasets related to process industry systems (pH neutralization and heat exchanger), whose estimation data undergo large contamination rates. The simulation results obtained by the RGP-t model indicates an impressive resilience to outliers and a superior capability to learn nonlinear dynamics directly from highly outlier-contaminated data in comparison to existing GP models.     

Specifying redundancy tactics as crosscutting concerns using aspect-oriented modeling

Various redundancy tactics can be modeled at the design stage of safety-critical systems thereby providing a set of fault-tolerance guidelines for subsequent development activities. However, existing approaches usually interweave redundancy tactics into the functional models making them complex and cluttered; the maintenance of such models is time-consuming and error-prone. To address this problem, we provide a modeling approach to separate the redundancy tactics from the base functional models using aspect-oriented modeling. More specifically, the conceptual models of the redundancy tactics and their semantic constraints are first defined for deriving the relevant aspects. Subsequently, a UML profile is proposed to specify the tactic aspects followed by mapping these concepts to the corresponding concepts of aspect-oriented modeling based on pre-defined principles. In accordance with our proposed profile, reuse directives are applied to handle the overlap of structural features between redundancy tactics and other kinds of tactic. Based on our tactic aspects and their configured attributes, a weaving algorithm is proposed to associate the tactic aspects with the base functional models. The proposed approach is compared with a traditional tactic modeling approach using two safety-critical systems, revealing that: 1) our approach significantly reduces the number of extra model elements needed in the tactic design stage; 2) our approach can largely avoid the impact of changing of the base functional model as the model evolves.     

Data generator for evaluating ETL process quality

Obtaining the right set of data for evaluating the fulfillment of different quality factors in the extract-transform-load (ETL) process design is rather challenging. First, the real data might be out of reach due to different privacy constraints, while manually providing a synthetic set of data is known as a labor-intensive task that needs to take various combinations of process parameters into account. More importantly, having a single dataset usually does not represent the evolution of data throughout the complete process lifespan, hence missing the plethora of possible test cases. To facilitate such demanding task, in this paper we propose an automatic data generator (i.e., Bijoux). Starting from a given ETL process model, Bijoux extracts the semantics of data transformations, analyzes the constraints they imply over input data, and automatically generates testing datasets. Bijoux is highly modular and configurable to enable end-users to generate datasets for a variety of interesting test scenarios (e.g., evaluating specific parts of an input ETL process design, with different input dataset sizes, different distributions of data, and different operation selectivities). We have developed a running prototype that implements the functionality of our data generation framework and here we report our experimental findings showing the effectiveness and scalability of our approach.     

A view framework for modeling and change validation of artifact-centric inter-organizational business processes

Over the past several years, more efficient approaches have been on increasing demands for designing, modeling, and implementing inter-organizational business processes. In the process collaboration across organizational boundaries, organizations still stay autonomic, which means each organization can freely modify its internal operations to meet its private goals while satisfying the mutual objectives with its partners. Recently, artifact-centric process modeling has been evidenced with higher flexibility in process modeling and execution than traditional activity-centric modeling methods. Although some efforts have been put to exploring how artifact-centric modeling facilitates the collaboration between organizations, the achievement is still far from satisfaction level, particularly in aspects of process modeling and validating. To fill in the gaps, we propose a view framework for modeling and validating the changes of inter-organizational business processes. The framework consists of an artifact-centric process meta-model, public view constructing mechanism, and private view and change validating mechanisms, which are specially designed to facilitate the participating organizations to customize their internal operations while ensuring the correctness of the collaborating processes. We also implement a software tool named Artifact-M to help organizations to automatically construct a minimal and consistent public view from their processes.     

Multicasting in the presence of aggregated deliveries

An increasing number of distributed systems relies on forms of message correlation, which result in atomic delivery of multiple messages aggregated by following process-specific criteria. Generally, more than one process is aggregating messages, implying that messages are multicast. While delivery guarantees for multicast scenarios with single message delivery are well understood, existing systems and models for aggregated deliveries either consider only unicast, centralized setups, or focus on efficiency thus providing only best-effort guarantees. This paper investigates the foundations of Multi-Delivery Multicast (MDMcast) in asynchronous distributed systems with crash-stop failures. We first describe a succinct aggregation model with a concise and generic predicate grammar for expressing conjunctions on messages and properties for a corresponding multicast primitive, which we term Conjunction-MDMcast (C-MDMcast). We show that for processes interested in identical conjunctions to achieve agreement on delivered messages, a total order on individual messages (or equivalent oracle) is not only useful but necessary, which is clearly opposed to single-message deliveries. We show this indirectly by exhibiting an algorithm implementing C-MDMcast on top of Total Order Broadcast (TOBcast) and vice-versa for a majority of correct processes. Then, we extend our predicate grammar with disjunctions, leading to the specification of Disjunction-MDMcast (D-MDMcast). We exhibit an algorithm implementing D-MDMcast, derived from our algorithm implementing C-MDMcast. We formalize several additional properties for both of our specifications, including ordering properties on aggregated messages and a notion of agreement capturing non-identical yet “related” conjunctions, and show how our respective algorithms implement these.