K. O. Chow

A petri-net-based synthesis methodology for use-case-driven system design

In use-case-driven system design, one need to derive from a set of use cases an integrated system design that meets at least two objectives. First, the system design must be consistent with the use cases in the sense that the functionalities of the use cases are exactly reflected. Second, the system design must be correct in the sense that the system is free from errors such as deadlock and capacity overflow. The latter is especially important for systems involving some concurrent, sequential, asynchronous, competitive and coordinated processes, such as manufacturing systems. In this paper, we propose a synthesis methodology for use-case-driven system design whereby both objectives are satisfied. In our methodology, use cases are specified as labelled Petri nets, in which the conditions, events and their causal relationships are explicitly represented. A system design is then derived by synthesising these nets into a single consistent whole. Our methodology has two distinctive features, namely, a formal specification of use cases and a rigorous and systematic process for deriving a system design whose correctness and consistency can be optimally achieved. We specifically show its application to manufacturing system design. Promising results are obtained.

Consistency Analysis on Lifecycle Model and Interaction Model

Two separate models, lifecycle model and interaction model, are generally adopted for specifying object behaviour in object-oriented system development. In this paper, we propose a Petri net-based formal method for analysing consistency between the two models at the logical level. This contributes to improving the consistency in the specification of object behaviour.

Compositional Synthesis of Augmented Marked Graphs

Augmented marked graphs possess some structural characteristics which are desirable for modelling shared-resource systems. This paper investigates the compositional synthesis of augmented marked graphs via a set of common resource places. It is shown that the synthesis preserves boundedness and conservativeness while liveness and reversibility can be preserved under a pretty simple condition. This can be applied to component-based system design, where a system is synthesised from a set of subsystems via common resources. By modelling the subsystems as augmented marked graphs and synthesising them via the corresponding resource places, based on the property-preserving features of this compositional synthesis, the properties of the integrated system can be readily derived.

Deriving scenarios of object interaction through Petri net

In object-oriented systems development, a lifecycle model and an interaction model are generally adopted in the specification of object behaviour. This specification by two separate models is liable to the problem of inconsistent specification between object lifecycle and interaction. We propose an approach to deriving scenarios of object interaction through a Petri net which is directly constructed from the lifecycle models of the interacting objects. The proposed approach offers an effective mechanism for deriving scenarios of object interaction without separately constructing an interaction model, and more important, encourages consistent specification between object lifecycle and interaction.

A Petri Net Based Method for Refining Object Oriented System Specifications

In object-oriented system design, requirements are given as use cases in the form of object interaction scenarios. One need to derive, from these object interaction scenarios, object-based behavioural specifications for implementation purposes. In this paper, a Petri-net-based method is proposed for the refinement process. The method starts with specifying the object interaction scenarios as labelled nets. These labelled nets are then synthesised into an integrated net. Duplicate labels are eliminated in order to attain a uniquely labelled net, on which object-based behavioural specifications are obtained as projections.

Analysis of Capacity Overflow for Manufacturing Systems

A manufacturing system is typically a shared resource system whose components never have unlimited capacities. In manufacturing system design, a major objective is to achieve a system which is free from capacity overflow. In this paper, a method is proposed for analysing if a system possesses this property. The method is based on augmented marked graphs. By modelling a manufacturing system as an augmented marked graph, we can analyse the possibility of capacity overflow using the properties of bounded augmented marked graphs

Elimination of duplicate labels in Petri-net-based system specification

Labelled Petri nets are commonly used for system specification where the locations of conditions are denoted as places with condition labels and the locations of events as transitions with event labels. It is often in a Petri-net-based specification that the same condition label or event label appears in multiple locations. As every condition is finally implemented as a unique state and every event as a unique operation, in order for the system specification to become useful for implementation, all duplicate condition labels and event labels must be eliminated. In this paper, we propose a method for eliminating the duplicate labels. Firing sequences are preserved so that the intended system behaviours will not be altered.

A feature-based approach for consistent object-oriented requirements specification

In object-oriented analysis, the problem domain is captured into a requirements specification where different class features are separately specified in a number of analysis models. Maintaining consistency on these class features is required, especially as the multiple-modelling trend of object-oriented analysis prevails. In this paper, three categories of consistency are identified using a feature-based approach. They include consistency on structural features, consistency on behavioural features, and consistency between structural and behavioural features. Consistency requirements are derived accordingly. These consistency requirements, taking the forms of correspondence, co-existence and restriction, bind the class features together to form a coherent logical framework of the target system so that different class features can be presented in a complementary and mutually conformable manner. Consistent object-oriented requirements specification can be achieved.

Incorporting Keyword-Based Filtering to Document Classification for Email Spamming

Email spamming causes serious problems in the Internet resulting in a huge waste of resources and attracting high attention from research society. Automatic document classification and keyword-based filtering are two kinds of techniques which have been applied to filter spam emails to achieve satisfactory results. This paper proposes a formal method by incorporating keyword-based filtering to document classification. To consider the potentially high cost of misclassification of an email to a spam email in real-word situation, a cost-sensitive evaluation metric is adopted to evaluate our approaches. We conducted extensive experiments in real-word data showing promising results.

Compositional Synthesis of Augmented Marked Graphs for Manufacturing System Integration

Augmented marked graphs possess a number of structural characteristics which are desirable for modelling manufacturing system components. This paper investigates the preservation of well-behaved system properties for compositional synthesis of augmented marked graphs via common resource places. By modelling the components of a manufacturing system as individual augmented marked graphs, based on the property-preservation of this compositional synthesis, essential properties of the integrated system can be readily derived.