João Paulo Barros

The Input-Output Place-Transition Petri Net Class and Associated Tools

Petri nets are a well-known formalism widely used in different application areas. Yet, the lack of adequate tools that can be integrated within engineering development frameworks are one major drawback. This paper identifies and justifies the characteristics of one class of Petri nets targeted for the modelling of automation systems and (networked) embedded systems, named as input-output Petri net (IOPT), and its representation using the Petri net markup language (PNML). The paper also presents a set of associated tools under development. This Petri net class, defined on top of the well-known place-transition Petri nets, is the common link across a set of tools under development, including a graphical editor, a state-space analyser for the verification of properties, conflict resolution through automatic arbiter generation, automatic code generators, simulator, among others. In this sense, the main goal of the proposed Petri net class and associated tools is to support the entire system development flow, from specification to implementation.

From Petri net models to VHDL implementation of digital controllers

Modeling of discrete-event systems using Petri net models is well-studied. Also, their usage for specification of digital controllers is widely used. Yet, it is recognized that we have a lack of tools when facing support for the implementation of these models, namely for automatic code generation. The paper briefly presents the FORDESIGN project that aims to develop a set of tools to contribute for filling this gap within automation systems and (networked) embedded systems development. The set of tools is based on a Petri net class, named as Input-Output Petri Net (IOPT), and its representation using the Petri Net Markup Language (PNML). The paper presents some rules used by an automatic code generator able to produce VHDL code starting with the PNML representation of the Petri net model.

Net model composition and modification by net operations: a pragmatic approach

Different tools often implement a single Petri net refinement or composition concept in different ways. This situation is undesirable from an engineering point of view. Here, we present a set of operations on nets based on the concepts of net instances and fusion sets, supporting the specification of net structures abstractions and net model transformations in an integrated and generic way. The operations are illustrated by composing a net model for a medium-sized control system. The same operations are then used to specify modifications to the initial model

Educating for mobile computing: addressing the new challenges

Computers that once filled rooms now fit in our pockets, and unlike their predecessors, mobile computers abound. The mobile industry is surging, with more smartphones being sold to consumers than PCs [17]. But does the rise of mobility impact computer science education? We claim that computer science educators must seriously consider mobility as they examine their curriculum. In this working group report, we offer a brief defense of why mobile computing belongs in our courses, summarize our survey of several hundred courses which already incorporate it, and discuss how educators might adopt it in their own courses. We hope that this work will help computer science educators make informed decisions about incorporating mobile computing into their courses and provide examples of such integration on different levels, ranging from individual projects or lecture topics to mobile computing as a learning context for an entire course.

A graphical editor for the input-output place-transition petri net class

This paper presents a set of under development tools associated with the FORDESIGN project, in particular an extension to the Petri nets graphical editor Snoopy. The project main purpose is to provide an adequate set of tools to be integrated within engineering development frameworks. The Snoopy graphical editor goal is to support editing capabilities to the input-output place-transition (IOPT) Petri net class models. These are targeted for the modelling of automation and embedded systems, where the Petri net markup language representation is extensively used.

Modifying Petri net models by means of crosscutting operations

Increasingly complex abstraction and composition constructs have been proposed for Petri nets, sometimes to the point that the quantity and diversity of net inscriptions seem to obscure the proclaimed advantages of Petri nets graphical representation. These constructs are oriented towards system synthesis but typically overlook the necessity of future model modifications due to unanticipated changes in requirements. These can imply modifications across several of the initially composed modules. We propose the use of two simple composition operations, net addition and net subtraction, that allow the introduction of the necessary modifications without being dependent on the net class or composition constructs in use. The operations can even be used concomitantly with the existent composition constructs. Three application examples are also presented which illustrate the use of the proposed operations in classic settings.

On structuring mechanisms for Petri nets based system design

This paper presents several structuring techniques applied to high-level Petri net models of embedded systems. Several modeling aspects are covered supporting the module concept, from the input and output structured modeling, and node structuring mechanism, to the more traditional hierarchical decomposition. Three types of Petri net nodes are used to support module representation: macro-places, macro-transitions and macro-blocks. Specific techniques to produce the executable model from the hierarchically structured model are presented. An application to an automation example is also presented.

Petri nets tools framework supporting FPGA-based controller implementations

This paper presents a set of tools having embedded systems co-design as the main target area of application and Petri nets as the underlying modeling formalism. The presented tools have been developed within the framework of the R&D FORDESIGN project, which will be briefly presented along with the proposed development methodology. The Petri net model, which is defined on top of the well-known place-transition Petri nets class, and represented in compliance with the PNML format, is the common link across the set of tools already developed (beta versions). These include a graphical editor, automatic code generators for different target languages (namely C and VHDL), tools for model composition and model decomposition (to support the usage of co-design techniques), and a configuration tool (where reconfigurable platforms, like FPGAs, and microcontroller architectures are considered as implementation platforms). The usage of some of the developed tools is briefly presented using an automation system example, in order to obtain specifications for a set of distributed controllers, and deployment into an FPGA-based implementation platform.

An Ecore based Petri net type definition for PNML IOPT models

In this paper we present a new Input-Output Place-Transition (IOPT) Petri net metamodel and its Petri Net Type Definition (PNTD) using a RELAX NG grammar. This new version introduces changes to the previous metamodel to ensure that the model representation follows the International Standard guidelines to extend PNML and to fully support automatic generation of models state space. The validation of this revised metamodel and the corresponding PNTD were made through case studies. The new concepts introduced in the metamodel have demonstrated their validity and usefulness, in the automatic generation of executable code and the state space. The correctness of the RELAX NG grammar was also validated through case studies.

Ecore representation for extending PNML for Input-Output Place-Transition nets

This paper presents a metamodel for the Input-Output Place-Transition nets (IOPT nets), a Petri net class targeted at controllers modeling. The proposed metamodel reuses many of the elements of the Petri Net Markup Language (PNML) metamodel, such as places, transitions, and arcs; it extends the PNML metamodel for Place/Transition nets to comprise concepts inherent to IOPT nets. The IOPT nets metamodel is described in Ecore format, putting IOPT nets in the puzzle of MDA artifacts taking benefit from the MDA infrastructure.