A brief review: Multimedia authoring modeling

Multimedia Authoring is a way to develop a multimedia presentation. Multimedia content includes images, sounds, videos, texts, and animations. The Kernel Mechanism of Multimedia Authoring consists of the Multimedia Authoring Programming Language and the Multimedia Authoring Model. Multimedia Authoring modeling is designed to enable the Multimedia Authoring function appropriately. Since the beginning of designing multimedia authoring tools, various studies were conducted to create a multimedia authoring model. Multimedia Authoring models that have been studied in existing research are Petri Nets, Hoare Logic, and LOTOS. The three models use different approaches. Petri Net uses a model based on graph calculations, Hoare logic uses mathematical logic, and LOTOS uses a formal specification language. Each of these models has been developed and modified to have higher capabilities. This model modification has advantages over the original model. This review article discusses the development and modifications of these models

Rigorous object-oriented analysis

Object-oriented methods for analysis, design and programming are commonly used by software engineers. Formal description techniques, however, are mainly used in a research environment. We have investigated how rigour can be introduced into the analysis phase of the software development process by combining object-oriented analysis (OOA) methods with formal description techniques. The main topics of this investigation are a formal interpretation of the OOA constructs using LOTOS, a mathematical definition of the basic OOA concepts using a simple denotational semantics and a new method for object- oriented analysis that we call the Rigorous Object-Oriented Analysis method (ROOA). The LOTOS interpretation of the OOA concepts is an intrinsic part of the ROOA method. It was designed in such a way that software engineers with no experience in LOTOS, can still use ROOA. The denotational semantics of the concepts of object-oriented analysis illuminates the formal syntactic transformations within ROOA and guarantees that the basic object- oriented concepts can be understood independently of the specification language we use. The ROOA method starts from a set of informal requirements and an object model and produces a formal object-oriented analysis model that acts as a requirements specification. The resulting formal model integrates the static, dynamic and functional properties of a system in contrast to existing OOA methods which are informal and produce three separate models that are difficult to integrate and keep consistent. ROOA provides a systematic development process, by proposing a set of rules to be followed during the analysis phase. During the application of these rules, auxiliary structures are created to help in tracing the requirements through to the final formal model. As LOTOS produces executable specifications, prototyping can be used to check the conformance of the specification against the original requirements and to detect inconsistencies, omissions and ambiguities early in the development process

Architectural notes: a framework for distributed systems development

This thesis develops a framework of methods and techniques for distributed systems development. This framework consists of two related domains in which design concepts for distributed systems are defined: the entity domain and the behaviour domain. In the entity domain we consider structures of functional entities and their interconnection, while in the behaviour domain we consider behaviour definition and structuring. An interaction in which we abstract from the particular responsibilities of the participating functional entities is considered as an action. Behaviours consist of actions, interactions and their relationships. Relationships between actions and interactions are defined in terms of causality relations. In each causality relation the conditions and constraints for an action or interaction to occur are defined. Two important behaviour structuring techniques have been identified from the possible ways causality relations can be distributed: causality-oriented behaviour composition and constraint-oriented behaviour composition. Causality-oriented behaviour composition consists of placing some conditions of an action and the action itself in different sub-behaviours. Constraint-oriented behaviour composition consists of placing parts of the conditions and constraints of an action in different sub-behaviours, such that this action is shared by these sub-behaviours. This thesis identifies milestones in the design process of distributed systems, as well as the design steps to move from one milestone to another. These design steps are characterized using the concepts of the entity and the behaviour domain. We identified two crucial design operations of the behaviour domain that support these design steps: behaviour refinement and action refinement. Behaviour refinement consists of introducing (internal) structure in the causality relations of reference actions of an abstract behaviour, but preserving their causality and exclusion relationships and their attribute values. Action refinement consists of replacing abstract actions by activities, such that the completion of these activities correspond to the occurrence of the abstract actions. One important characteristic of action refinement is the possibility of distributing attribute values of the abstract actions over actions of the activities that replace them in the concrete behaviours. The area of research, scope and objectives of this thesis are discussed in Chapter 1. The concept of design culture and its elements is introduced in this chapter in order to provide an overview of the important aspects of the design process. Entity domain, behaviour domain, and design milestones are introduced and discussed in Chapter 2. This chapter also discusses the global objectives of design steps, and the abstraction obtained by considering interactions between cooperating functional entities as actions of the interaction system between these entities. Action, action attributes, causality and exclusion are discussed in Chapter 3. This chapter shows how a behaviour can be defined in terms of the causality relations of its actions in a monolithic form. Causality-oriented behaviour composition is discussed in Chapter 4. Entries and exits of a behaviour are the mechanisms that make it possible to assign parts of a condition of an action and the action itself to different sub-behaviours. Constraint-oriented behaviour composition is discussed in Chapter 5. Decomposition possibilities of monolithic behaviours are systematically studied in this chapter. Behaviour refinement is discussed in Chapter 6. This chapter defines a method to obtain an abstraction of a concrete behaviour. This method can be used to check whether the concrete behaviour corresponds to a certain abstract behaviour. Action refinement is discussed in Chapter 7. This chapter identifies some activity forms, and define the rules for considering these activities as implementations of an abstract action. These rules are used in a method to derive an abstraction of a concrete behaviour in which the abstract actions are implemented as activities. This method can be used to check whether the concrete behaviour corresponds to a certain abstract behaviour. Chapter 8 discusses a design example that is meant to illustrate the use of our design concepts. The example is an interaction server, which is a component that supports the interaction between multiple functional entities. Chapter 9 draws some conclusions and revisits the design milestones of Chapter 2, showing alternatives for the design trajectory which have been created with the use of actions and interactions in a single framework

Action Relations:Basic Design Concepts for Behaviour Modelling and Refinement

This thesis presents basic design concepts, design methods and a basic design language for distributed system behaviours. This language is based on two basic concepts: the action concept and the causality relation concept. Our methods focus on behaviour refinement, which consists of replacing an abstract behaviour by a more concrete behaviour, such that the concrete behaviour conforms to the abstract behaviour. An important idea underlying this thesis is that an effective design methodology should be based on a properly chosen and precisely defined set of basic design concepts. Properly chosen design concepts represent essential system conceptions (mental images) that are derived from the real world and allow a designer to conceive and structure the essential characteristics of a system. The set of basic design concepts and their combination rules is called a basic design model. We explain how a design methodology supported by design notations and automated tools depends on the basic design model. We introduce and motivate a limited set of basic design concepts that are necessary to design distributed systems. These concepts are structured into two related conceptual domains: the entity domain and the behaviour domain. This thesis focuses on the behaviour domain, which consists of the action concept, the interaction concept and the concept of causality relation. Therefore, we elaborate the action and interaction concepts in more detail and give a formal definition of these concepts. The elaboration of the causality relation concept comprises the main part of this thesis. In order to enable a systematic and modular development of the causality relation concept, we identify the important characteristics of relations between actions and structure these characteristics in an abstraction hierarchy. An action models the essential characteristics of a unit of activity that is performed by a single entity. We consider the following characteristics of an activity as essential: the result that is established by the activity, the moment at which the activity is finished and makes its total result available, and the location at which this result is made available. These characteristics are modelled by means of the information, time and location attributes of an action, respectively. We consider an interaction as a refinement of an action, which models how an activity is performed through the cooperation of multiple entities. A causality relation defines one or more alternative conditions for the occurrence of an action in terms of how this action depends on the occurrences or non-occurrences of other actions. An action occurrence is caused by (or depends on) only one of its alternative conditions, although multiple of these conditions can be satisfied at the same time. We consider the uncertainty or probability that an action occurs when one (or more) of its alternative conditions are satisfied as an important concept in the design of relations between activities. This concept is represented by the probability attribute, which defines, for each alternative 390 Summary condition of an action, the probability that the action occurs when this condition is satisfied. We distinguish three types of probability attributes: (i) the uncertainty attribute supports two uncertainty values: must and may, (ii) the integral probability attribute quantifies these uncertainty values, such that the must value corresponds to probability value 1, and the may value corresponds to a probability value in the range (0..1), and (iii) the stochastic probability attribute uses the time attribute of an action as a stochastic variable, such that a probability distribution function defines for the time period in which the action is allowed to occur, the probability that the action actually occurs. We start with an initial definition of the causality relation concept that supports the design of temporal ordering relations between actions, including the uncertainty attribute. Four elementary causality conditions are defined: the start condition, the enabling condition, the disabling condition and the synchronization condition. These elementary conditions can be composed into more complex causality conditions using the conjunction (and-) and disjunction (or-) operators. The disjunction operator is used to define multiple alternative causality conditions for an action. The uncertainty attribute defines, for each of these alternative conditions, whether the action must or may occur when this condition is satisfied. The initial definition of the causality relation concept is extended with the information, location and time attribute. This extension supports the design of the following type of constraints for each of these attributes: (i) the range of possible values that can be established in an action, (ii) how the value of an action depends on the values established in other actions, and (iii) how the occurrence of an action depends on the values established in other actions. Constraints involving different attribute types are also allowed, e.g., the time and location value established in an action may be referred to as information values by another action. The integral and stochastic probability attribute can be used instead of the uncertainty attribute to quantify the uncertainty of action occurrences. Two interpretations of these probability attributes are distinguished: (i) the simple interpretation defines for each alternative condition of an action the probability that the action occurs when this condition is satisfied, and (ii) the extended interpretation defines for each alternative condition of an action the probability that the occurrence of the action is caused by this condition once this condition enables the action. The extended interpretation allows one to model the probability of individual actions in, e.g., choice, disabling and interleaving relations. In order to define the formal semantics of causality relations, a so called execution model is introduced. In this model, a behaviour is defined by enumerating all possible executions of this behaviour. An execution represents the outcome of a possible run of a system that performs a specified behaviour. This outcome comprises the actions that have occurred, the information, time and location values that have been established in these actions, and how action occurrences are related in the particular execution. An execution also gets one or more probability values, which represent the probability that this execution is the outcome of a system run. In this respect, a behaviour is considered an experiment and an execution is considered a possible outcome of this experiment. The sum of the probability of all possible executions of a behaviour is equal to 1. Based on the basic design language, we present an integrated set of methods to perform behaviour refinement. These methods support two basic types of behaviour refinement: 391 causality refinement, in which causality relations between abstract actions are replaced by causality relations involving their corresponding concrete actions and some inserted actions, and action refinement, in which an abstract action is replaced by an activity involving multiple concrete actions and their causality relations. The methods are based on the assessment of the conformance relation between the abstract behaviour and the concrete behaviour that is obtained from the abstract behaviour by means of causality refinement or action refinement. This assessment involves the determination of the abstraction of the concrete behaviour and the comparison of this abstraction with the original abstract behaviour. Rules to perform the abstraction and comparison operations have been developed. In this thesis we extend the basic design language with the causality-oriented structuring technique defined in [16]. This technique allows one to structure a complex behaviour in terms of simpler sub-behaviours and their relationships. In order to model (infinitely) repetitive behaviours, this technique is extended with the means to (dynamically) create multiple instances of a single sub-behaviour (type) definition, including the means to refer unambiguously to each individual behaviour instance. The ideas presented in this thesis are applied to two case studies. We apply our behaviour refinement method to the design of a system that supports a client-server interaction. At the highest abstraction level we assume that direct interactions between the client application and the server application are possible. At a lower abstraction level we implement these interactions using a federation of remote traders, which communicate via a common communication infrastructure. We also apply our basic design language to the modelling of the behaviour of the OSI Connection-oriented Transport Service. This case study also includes the modelling of timing and probability characteristics imposed by the QoS parameters of the transport service

Quality of (Digital) Services in e-Government

Internet growth in the nineties supported government ambition to provide better services to citizens through the development of Information and Communication Technologies based solutions. Thanks to the Lisbon conference, which in 2000 covered and investigated this topic, e-government has been recognized as one of the major priorities in Public Administration innovation process. As a matter of\ud fact in the last 10 years the number of services provided to citizens through Information and Communication Technologies has increased rapidly. Nevertheless the increasing rate, the access and usage of digital services do not follow the same trend. Nowadays Public Administrations deliver many electronic services which\ud are seldom used by citizens. Different reasons contribute to the highlighted situation.\ud The main assumption of the thesis is that quality of e-government digital services strongly affects real access to services by citizens. According to the complexity of quality in e-government, one of the main challenges was to define a suitable quality model. To reach such aim, domain-dependent characteristics on the services delivery have been investigated. The defined model refers to citizen,\ud technology and service related quality characteristics. Correspondingly a suitable way to represent, assess, and continuously improve services quality according to\ud such domain requirements has been introduced.\ud Concerning the service related quality aspects a methodology and a tool permitting to formally and automatically assess the quality of a designed service with\ud respect to the quality model has been defined. Starting from an user friendly notation, both for service and quality requirements, the proposed methodology has\ud been implemented as an user friendly tool supported by a mapping from user friendly notations to formal language. The tool allows to verify formally via model checking, if the given service satisfies one by one the quality requirements addressed by the quality model.\ud Additionally in some case an unique view on e-government service quality is quite useful. A mathematical model provides a single value for quality starting from the assessment of all the requirements defined in the quality model. It relies on the following activities: homogeneity, interaction and grouping.\ud A set of experiments has been performed in order to validate the goodness of the work. Services already implemented in a local Public Administration has\ud been considered. Literature review and domain experts knowledge were the main drivers of this work. It proofs the goodness of the quality model, the application of formal techniques in the complex field of study such as e-government and the quality aggregation via the mathematical model.\ud This thesis introduces advance research in e-government by providing the contributions that quality oriented service delivery in Public Administration promotes services used by the citizens. Further applications of the proposed approaches could be investigated in the areas of practical benchmarking and Service Level Agreement specification

Animation prototyping of formal specifications

At the present time one of the key issues relating to the design of real-time systems is the specification of software requirements. It is now clear that specification correctness is an essential factor for the design and implementation of high quality software. As a result considerable emphasis is placed on producing specifications which are not only correct, but provably so. This has led to the application of mathematically-based formal specification techniques in the software life-cycle model. Unfortunately, experience in safety-critical systems has shown that specification correctness is not, in itself, sufficient. Such specifications must also be comprehensible to all involved in the system development. The topic of this thesis—Animation Prototyping—is a methodology devised to make such specifications understandable and usable. Its primary objective is to demonstrate key properties of formal specifications to non-software specialists. This it does through the use of computer-animated pictures which respond to the dictates of the formal specification. [Continues.