Process Evolution based on Transformation of Algebraic High-Level Nets with Applications to Communication Platforms

Algebraic High-Level (AHL) nets are a well-known modelling technique based on Petri nets with algebraic data types, which allows to model the communication structure and the data flow within one modelling framework. Transformations of AHL-nets – inspired by the theory of graph transformations – allow in addition to modify the communication structure. Moreover, high-level processes of AHL-nets capture the concurrent semantics of AHL-nets in an adequate way. In this paper we show how to model the evolution of communication platforms and scenarios based on transformations of algebraic high-level nets and processes. All constructions and results are illustrated by a running example showing the evolution of Apache Wave platforms and scenarios. The evolution of platforms is modelled by the transformation of AHL-nets and that of scenarios by the transformation of AHL-net processes.Our main result is a construction for the evolution of AHL-processes based on the evolution of the corresponding AHL-net. This result can be used to transform scenarios in a communication platform according to the evolution of possibly multiple actions of the platform

Algebraic High-Level Nets and Processes Applied to Communication Platforms

Petri nets are well-known to model communication structures and algebraic specifications for modeling data types. Algebraic High-Level (AHL) nets are defined as integration of Petri nets with algebraic data types, which allows to model the communication structure and the data flow within one modelling framework. Transformations of AHL-nets – inspired by the theory of graph transformations – allow in addition to modify the communication structure. Moreover, highlevel processes of AHL-nets capture the concurrent semantics of AHL-nets in an adequate way. Altogether we obtain a powerful integrated formal specification technique to model and analyse all kinds of communication based systems. In this paper we give a comprehensive introduction of this framework. This includes main results concerning parallel independence of AHL-transformations and the transformation and amalgamation of AHL-occurrence nets and processes. Moreover, we show how this can be applied to model and analyse modern communication and collaboration platforms like Google Wave and Wikis. Especially we show how the Local Church-Rosser theorem for AHL-net tranformations can be applied to ensure the consistent integration of different platform evolutions. Moreover, the amalgamation theorem for AHL-processes shows under which conditions we can amalgamate waves of different Google Wave platforms in a compositional way

Modelling Evolution of Communication Platforms and Scenarios based on Transformations of High-Level Nets and Processes : Extended Version

Algebraic High-Level (AHL) nets are a well-known modelling technique based on Petri nets with algebraic data types, which allows to model the communication structure and the data flow within one modelling framework. Transformations of AHL-nets – inspired by the theory of graph transformations – allow in addition to modify the communication structure. Moreover, high-level processes of AHL-nets capture the concurrent semantics of AHL-nets in an adequate way. Altogether we obtain a powerful integrated formal specification technique to model and analyse all kinds of communication based systems, especially different kinds of communication platforms. In this paper we show how to model the evolution of communication platforms and scenarios based on transformations of Algebraic High-Level Nets and Processes. All constructions and results are illustrated by a running example showing the evolution of Apache Wave platforms and scenarios. The evolution of platforms is modelled by the transformation of AHL-nets and that of scenarios by the transformation of AHL-net processes. The first main result shows under which conditions AHL-net processes can be extended if the corresponding AHL-net is transformed. This result can be applied to show the extension of scenarios for a given platform evolution. The second main result shows how AHL-net processes can be transformed based on a special kind of transformation for AHL-nets, corresponding to action evolution of platforms. Finally, we briefly discuss the case of multiple action evolutions

Not cool, calm or collected: Using emotional language to detect COVID-19 misinformation

COVID-19 misinformation on social media platforms such as twitter is a threat to effective pandemic management. Prior works on tweet COVID-19 misinformation negates the role of semantic features common to twitter such as charged emotions. Thus, we present a novel COVID-19 misinformation model, which uses both a tweet emotion encoder and COVID-19 misinformation encoder to predict whether a tweet contains COVID-19 misinformation. Our emotion encoder was fine-tuned on a novel annotated dataset and our COVID-19 misinformation encoder was fine-tuned on a subset of the COVID-HeRA dataset. Experimental results show superior results using the combination of emotion and misinformation encoders as opposed to a misinformation classifier alone. Furthermore, extensive result analysis was conducted, highlighting low quality labels and mismatched label distributions as key limitations to our study

Algebraic Approach to Timed Petri Nets

One aspect often needed when modelling systems of any kind is time-based analysis, especially for real-time or in general time-critical systems. Algebraic place/transition (P/T) nets do not inherently provide a way to model the passing of time or to restrict the firing behaviour with regards to passing time. In this paper, we present an extension of algebraic P/T nets by adding time durations to transitions and timestamps to tokens. We define categories for different timed net classes and functorial relations between them. Our first result is the definition of morphisms preserving firing behaviour for all timed net classes. As second result, we define structuring techniques for timed P/T nets in a way that our category fulfills the properties of M-adhesive systems, a general categorical framework for structuring and transforming high-level algebraic structures. We demonstrate our approach by applying it to model a real-time communication network

An Algebraic Approach to Timed Petri Nets with Applications to Communication Networks

In this report, we define a formalism for a time-extension to algebraic place/transition (P/T) nets. This allows time durations to be assigned to the transitions of a P/T net, representing delays present in the systems that are being modelled, which in turn influence (restrict) the firing behaviour of the nets. This is especially useful when modelling time-dependent systems. The new contribution of this approach is the definition of categories for the timed net classes of timed P/T nets, timed P/T systems and timed P/T states. Moreover, we define functorial relations between these categories as well as functorial relations to categories of untimed P/T nets and systems. The first main result is the formalisation of morphisms for all three net classes that preserve firing behaviour. The second main result is the equivalence of the categories of timed P/T systems and states, establishing a relation between structurally identical nets with a time offset. As a third main result we formalise structuring techniques for timed P/T nets and show that timed P/T nets fit in the framework of M-adhesive categories

Formalization of Petri Nets with Individual Tokens as Basis for DPO Net Transformations

Reconfigurable place/transition systems are Petri nets with initial markings and a set of rules which allow the modification of the net structure during runtime. They have been successfully used in different areas like mobile ad-hoc networks. In most of these applications the modification of net markings during runtime is an important issue. This requires the analysis of the interaction between firing and rule-based modification. For place/transition systems this analysis has been started explicitly without using the general theory of M-adhesive transformation systems, because firing cannot be expressed by rule-based transformations for P/T systems in this framework. This problem is solved in this paper using the new approach of P/T nets with individual tokens. In our main results we show that on one hand this new approach allows to express firing by transformation via suitable transition rules. On the other hand transformations of P/T nets with individual tokens can be shown to be an instance ofM-adhesive transformation systems, such that several well-known results, like the local Church-Rosser theorem, can be applied. This avoids a separate conflict analysis of token firing and transformations. Moreover, we compare the behavior of P/T nets with individual tokens with that of classical P/T nets. Our new approach is also motivated and demonstrated by a network scenario modeling a distributed communication system

Finitary M-adhesive categories

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Finitary M-adhesive categories are M-adhesive categories with finite objects only, where M-adhesive categories are a slight generalisation of weak adhesive high-level replacement (HLR) categories. We say an object is finite if it has a finite number of M-subobjects. In this paper, we show that in finitary M-adhesive categories we not only have all the well-known HLR properties of weak adhesive HLR categories, which are already valid for M-adhesive categories, but also all the additional HLR requirements needed to prove classical results including the Local Church-Rosser, Parallelism, Concurrency, Embedding, Extension and Local Confluence Theorems, where the last of these is based on critical pairs. More precisely, we are able to show that finitary M-adhesive categories have a unique ε'-M factorisation and initial pushouts, and the existence of an M-initial object implies we also have finite coproducts and a unique ε' -M pair factorisation. Moreover, we can show that the finitary restriction of each M-adhesive category is a finitary M-adhesive category, and finitarity is preserved under functor and comma category constructions based on M-adhesive categories. This means that all the classical results are also valid for corresponding finitary M-adhesive transformation systems including several kinds of finitary graph and Petri net transformation systems. Finally, we discuss how some of the results can be extended to non-M-adhesive categories

Finitary M-Adhesive Categories : Unabridged Version

Finitary M-adhesive categories are M-adhesive categories with finite objects only, where the notion M-adhesive category is short for weak adhesive high-level replacement (HLR) category. We call an object finite if it has a finite number of M-subobjects. In this paper, we show that in finitary M-adhesive categories we do not only have all the well-known properties of M-adhesive categories, but also all the additional HLR-requirements which are needed to prove the classical results for M-adhesive systems. These results are the Local Church-Rosser, Parallelism, Concurrency, Embedding, Extension, and Local Confluence Theorems, where the latter is based on critical pairs. More precisely, we are able to show that finitary M-adhesive categories have a unique E-M factorization and initial pushouts, and the existence of an M-initial object implies in addition finite coproducts and a unique E'-M' pair factorization. Moreover, we can show that the finitary restriction of each M-adhesive category is a finitary M-adhesive category and finitariness is preserved under functor and comma category constructions based on M-adhesive categories. This means that all the classical results are also valid for corresponding finitary M-adhesive systems like several kinds of finitary graph and Petri net transformation systems. Finally, we discuss how some of the results can be extended to non-M-adhesive categories