Modeling interactive memex-like applications based on self-modifiable petri nets

This paper introduces an interactive Memex-like application using a self-modifiable Petri Net model – Self-modifiable Color Petri Net (SCPN). The Memex (“memory extender”) device proposed by Vannevar Bush in 1945 focused on the problems of “locating relevant information in the published records and recording how that information is intellectually connected.” The important features of Memex include associative indexing and retrieval. In this paper, the self-modifiable functions of SCPN are used to achieve trail recording and retrieval. A place in SCPN represents a website and an arc indicates the trail direction. Each time when a new website is visited, a place corresponding to this website will be added. After a trail is built, users can use it to retrieve the websites they have visited. Besides, useful user interactions are supported by SCPN to achieve Memex functions. The types of user interactions include: forward, backward, history, search, etc. A simulator has been built to demonstrate that the SCPN model can realize Memex functions. Petri net instances can be designed to model trail record, back, and forward operations using this simulator. Furthermore, a client-server based application system has been built. Using this system, a user can surf online and record his surfing history on the server according to different topics and share them with other users

On Modelling and Analysis of Dynamic Reconfiguration of Dependable Real-Time Systems

This paper motivates the need for a formalism for the modelling and analysis of dynamic reconfiguration of dependable real-time systems. We present requirements that the formalism must meet, and use these to evaluate well established formalisms and two process algebras that we have been developing, namely, Webpi and CCSdp. A simple case study is developed to illustrate the modelling power of these two formalisms. The paper shows how Webpi and CCSdp represent a significant step forward in modelling adaptive and dependable real-time systems.Comment: Presented and published at DEPEND 201

Substitution-based approach for linguistic steganography using antonym

Steganography has been a part of information technology security since a long time ago. The study of steganography is getting attention from researchers because it helps to strengthen the security in protecting content message during this era of Information Technology. In this study, the use of substitution-based approach for linguistic steganography using antonym is proposed where it is expected to be an alternative to the existing substitution approach that using synonym. This approach still hides the message as existing approach but its will change the semantic of the stego text from cover text. A tool has been developed to test the proposed approach and it has been verified and validated. This proposed approach has been verified based on its character length stego text towards the cover text, bit size types of the secret text towards the stego text and bit size types of the cover text towards the stego text. It has also been validated using four parameters, which are precision, recall, f-measure, and accuracy. All the results showed that the proposed approach was very effective and comparable to the existing synonym-based substitution approach

Requirement Validation for Embedded Systems in Automotive Industry Through Modeling

Requirement validation contributes significantly toward the success of software projects. Validating requirements is also essential to ensure the correctness of embedded systems in the auto industry. The auto industry emphasizes a lot on the verification of car designs and shapes. Invalid or erroneous requirements lead to inappropriate designs and degraded product quality. Considering the required expertise and time for requirement validation, significant attention is not devoted to verification and validation of requirements in the industry. Currently, the failure ratio of software projects is significantly higher and the key reason for that appears to be the inappropriate and invalidated requirements at the early stages in the projects. To that end, we propose a model-based approach that uses the existing V&V model. Through virtual prototyping, the proposed approach eliminates the need to validate the requirements after each stage of the project. Consequently, the model is validated after the design phase and the errors in requirements are detected at the earliest stage. In this research, we performed two different case studies for requirement validation in the auto industry by using a modeling-based approach and formal technique using Petri nets. A benefit of the proposed modeling-based approach is that the projects in the auto industry domain can be completed in less time due to effective requirements validation. Moreover, the modeling-based approach minimizes the development time, cost and increases productivity because the majority of the code is automatically generated using the approach

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

Building safe software

Murphy is a set of techniques and tools under investigation for their potential in enhancing the safety of software. This paper describes some of the work which has been done and some which is planned

Activity diagrams: a formal framework to model business processes and code generation

Activity Diagram is an important component of the set of diagrams used in UML. The OMG document on UML 2.0 proposes a Petri net based semantics for Activity Diagrams. While Petri net based approach is useful and interesting, it does not exploit the underlying inherent reactive behaviour of activity diagrams. In the first part of the paper, we shall capture activity diagrams in synchronous language framework to arrive at executional models which will be useful in model based design of software. This also enables validated code generation using code generation mechanism of synchronous language environments such as Esterel and its programming environments. Further, the framework leads to scalable verification methods. The traditional semantics proposed in OMG standard need enrichment when the activities are prone to failure and need compensating actions. Such extensions are expected to have applications in modelling complex business processes. In the second part of the paper, we propose an enrichment of the UML Activity Diagrams that include compensable actions. We shall use some of the foundations on Compensable Transactions and Communicating Sequential Processes due to Tony Hoare. This enriched formalism allows UML Activity Diagrams to model business processes that can fail and require compensating actions