Mohamed Dahchour

Materialization and its metaclass implementation

Materialization is a powerful and ubiquitous abstraction pattern for conceptual modeling that relates a class of categories (e.g., models of cars) and a class of more concrete objects (e.g., individual cars). This paper presents materialization as a generic relationship between two classes of objects and describes an abstract implementation of it. The presentation is abstract in that it is not targeted at a specific object system. The target system is supposed to provide: 1) basic object-modeling facilities, supplemented with an explicit metaclass concept and 2) operations for dynamic schema evolution like creation or deletion of a subclass of a given class and modification of the type of an attribute of a class. The presentation is generic in that the semantics of materialization is implemented in a metaclass, which is a template to be instantiated in applications. Application classes are created as instances of the metaclass and they are thereby endowed with structure and behavior consistent with the generic semantics of materialization.

A Generic Role Model for Dynamic Objects

The role generic relationship for conceptual modeling relates a class of objects (e.g., persons) and classes of roles (e.g., students, employees) for those objects. The relationship is meant to capture temporal aspects of real-world objects while the common generalization relationship deals with their more static aspects. This paper presents a generic role model, where the semantics of roles is defined at both the class and the instance levels. The paper also discusses the interaction between the role relationship and generalization, and it attempts to clarify some of their similarities and differences.

A role model and its metaclass implementation

The role generic relationship for conceptual modeling relates a class of objects (e.g., persons) and classes of roles (e.g., students, employees) for those objects, The role relationship is meant to capture dynamic aspects of real-world objects while the usual generalization relationship deals with their more static aspects. Therefore, to take into account both static and dynamic aspects, object languages and systems must somehow support both relationships. This paper presents a generic role model where the semantics of roles is defined at both the class and the instance levels. It discusses the interaction between the role relationship and generalization, and it attempts to clarify some of their similarities and differences. The introduction of roles as an abstraction mechanism in the overall software development lifecycle is reviewed. The paper then proposes a comprehensive implementation for the role relationship, with the help of a metaclass mechanism. Our implementation is illustrated along the lines of the VODAK modeling language. Thus, the semantics of our role model is implemented in a metaclass that is a template to be instantiated in applications. Application classes are then created as instances of the metaclass and they are thereby endowed with structure and behavior consistent with the semantics of roles.

Generic relationships in information modeling

Generic relationships are abstraction patterns used for structuring information across application domains. They play a central role in information modeling. However, the state of the art of handling generic relationships leaves open a number of problems, like differences in the definition of some generic relationships in various data models and differences in the importance given to some generic relationships, considered as first-class constructs in some models and as special cases of other relationships in other models. To address those problems, we define a list of dimensions to characterize the semantics of generic relationships in a clear and systematic way. The list aims to offer a uniform and comprehensive analysis grid for generic relationships, drawn from a careful analysis of commonalities and differences among the generic relationships discussed in the literature. The usefulness of those dimensions is illustrated by reviewing significant generic relationships, namely, materialization, role, aggregation, grouping, and ownership. Based on those dimensions, a new metamodel for relationships is proposed.

Formalizing Materialization Using a Metaclass Approach

Materialization is a powerful and ubiquitous abstraction pattern for conceptual modeling. Intuitively, it relates a class of categories (e.g., models of cars) and a class of more concrete objects (e.g., individual cars). This paper formalizes the semantics of materialization using the metaclass approach of the TELOS data model. Formulas can be uniformly attached to classes, metaclasses, and meta-attributes to enforce integrity constraints and deductive rules relevant to materialization semantics. The paper also proposes some suggestions for extending TELOS to capture some materialization semantics which cannot be represented with the available constructs.

Definition and Application of Metaclasses

Metaclasses are classes whose instances are themselves classes. Metaclasses are generally used to define and query information relevant to the class level. The paper first analyzes the more general. term meta and gives some examples of its use in various application. domains. Then, it focuses on the description of metaclasses. To help. better understand metaclasses, the paper suggests a set of criteria. accounting for the variety of metaclass definitions existing in the literature. The paper finally presents the usage of metaclasses and discusses some questions raised about them.

Project portfolio management information systems (PPMIS) information entropy based approch to prioritize PPMIS

Project portfolio management information systems (PPMIS) can have a significant impact on the operation and development of a company. Therefore, the selection of one or more PPMIS of all possible is an important and difficult task for decision makers. The variety of functionalities and features offered, and changes in the needs of each organization, make the prioritization of an appropriate PPMIS a complicated multi-criteria decision problem. The complexity of the problem is increased by the multiplicity of actors involved in the prioritization process. These multi stakeholders often cannot accurately assess their preferences judgment of candidate PPMIS. To meet these limitations, this paper presents one of PPMIS prioritization approach that applies an information entropy method. This approach takes into account the imprecision of data and the uncertainty of the judgments of assessors when evaluating PPMIS for the needs of the organization. The approach is demonstrated through a case study to support the organization to prioritize and select a suitable PPMIS.

Towards a Framework for the Analysis and Evaluation of Computational Trust Models in Multi-agent Systems

In open dynamic multi-agent systems, trust is commonly considered as a critical concept to be handled and managed. Computational trust models are a kinds of formal models that have been proposed to manage trust in such situation. These models present a new form of distributed intelligence in virtual societies and collective intelligence. However, the diversity of those models makes user confused about which one to choose. Different testbeds have been established to evaluate trust and reputation models and verify their robustness and efficiency. However, a lack of flexibility to handle scenarios related to multi-context trust models arise with those testbeds. We present in this paper a framework for evaluating computational trust models that provides to users more flexibility while comparing trust models in open systems and shows analysis results in chart diagrams. The ultimate objective is to evaluate and classify available computational trust models.

Analysis of common business rules in BPMN process models using business rule language

Process models describe graphically, events, activities, control flow and dataflow logic that constitute a business process. Nevertheless most graphical modeling notations required by organization stakeholders such as BPMN, are not provided with a formal semantics, limiting the possibility of analysis to informal approaches such as observation techniques. While most of the existing formal approaches for BPMN models verification focus on the control-flow, very few has treated the Business rules verification angle. In this paper, we present a new approach that uses the Business Rule Language (BRL) which helps us express several common types of business rules that could be verified by a DFS algorithm adapted for the BPMN standard. The proposed approach has been implemented as an Eclipse plugin called, “BPMN Process Analysis”.

A Constraint-based Approach for Checking Vertical Inconsistencies between Class and Sequence UML Diagrams

The modern software development processes enable evolving software systems and refining models across software life cycle. However, these evolution attitudes may lead to some consistency problems among models at different levels of abstraction. Hence, it is required to discover and detect the potential inconsistencies occurring in models when developing a system. This paper focuses on checking the vertical consistency of UML models using an approach based on defining constraints at the meta-level. These constraints are expressed using EVL (Epsilon Validation Language) to ensure the consistency of models. Representative examples of constraints for checking vertical inconsistencies between class and sequence diagrams are proposed to illustrate our contribution.