Slides for a presentation at Fondation UQAC, February 2012 (the half-dozen words throughout the slides are in French). It is intended to be a gentle introduction to the concept of software bugs, their cost, the increasing complexity of computer programs and some methods to analyze them mathematically.
I leave the viewer to guess what was the speech that accompanied each drawing. Enjoy!
We introduce a formal notation for the processing of event traces called Stream Logic (SL). A monitor evaluates a Boolean condition over an input trace, while a filter outputs events from an input trace depending on some monitor's verdict; both constructs can be freely composed. We show how all operators of Linear Temporal Logic, as well as the parametric slicing of an input trace, can be written as Stream Logic constructs.
Causality in Message-Based Interface Contracts: A Temporal Logic "Whodunit"Sylvain Hallé
Interface contracts are sets of constraints specifying valid exchanges of messages between two or more peers. A contract violation occurs when one of the peers fails to fulfil one of these constraints and emits a message that is not a valid continuation of a message "trace". In some cases, the message that directly exposes the violation turns out to be the last of a succession of forced moves, while the "root cause" of the violation resides earlier in the trace and may emanate from a different peer. We formally define the notion of causality for interface contracts expressed in a first-order extension of Linear Temporal Logic. In particular, we show how the detection of root causes reduces to satisfiability solving of a precise set of formulæ. An experimental setup shows how causality can be analyzed automatically on a pre-recorded message trace.
Graph Methods for Generating Test Cases with Universal and Existential Constr...Sylvain Hallé
We introduce a generalization of the t -way test case generation problem, where parameter t is replaced by a set Φ of Boolean conditions on attribute values. We then present two reductions of this problem to graphs; first, to graph colouring, where we link the the minimal number of tests to the chromatic number of some graph; second, to hypergraph vertex covering. This latter formalization allows us to handle problems with constraints of two kinds: those that must be true for every generated test case, and those that must be true for at least one test case. Experimental results show that the proposed solution produces test suites of slightly smaller sizes than a range of existing tools, while being more general: to the best of our knowledge, our work is the first to allow existential constraints over test cases.
Chasing Bugs with the BeepBeep Event Stream ProcessorSylvain Hallé
Runtime verification is the process of observing a sequence of events generated by a running system and comparing it to some formal specification for potential violations. We show how the use of the BeepBeep event stream processor can greatly speed up the testing phase of a video game under development, by automating the detection of bugs when the game is being played. This process generalizes to a wide number of other use cases, including web application debugging and network intrusion detection.
A Case for "Piggyback" Runtime MonitoringSylvain Hallé
A runtime monitor enforcing a constraint on sequences of method calls on an object must keep track of the state of the sequence by updating an appropriate state machine. The present paper stems from the observation that an object's member fields must already contain an encoding of that state machine, and that a monitor essentially duplicates operations that the object performs internally. Rather than maintain a state machine in parallel, the paper puts forward the concept of "piggyback" runtime monitoring, where the monitor relies as much as possible on the object's own state variables to perform its task. Experiments on real-world benchmarks show that this approach greatly simplifies the monitoring process and drastically reduces the incurred runtime overhead compared to classical solutions.
Activity Recognition Through Complex Event Processing: First Findings Sylvain Hallé
The activities of daily living of a patient in a smart home environment can be detected to a large extent by the real-time analysis of characteristics of the habitat's electrical consumption. However, reasoning over the conduct of these activities occurs at a much higher level of abstraction than what the sensors generally produce. In this paper, we leverage the concept of Complex Event Processing (CEP), in which low-level data streams are progressively transformed into higher-level ones, to the task of activity recognition. We show how the use of an appropriate representation for each level of abstraction can greatly simplify the process. We also report on the use of an existing event stream processor to successfully implement the complete chain, from low-level sensor data up to a sequence of discrete and high-level actions.
We introduce a formal notation for the processing of event traces called Stream Logic (SL). A monitor evaluates a Boolean condition over an input trace, while a filter outputs events from an input trace depending on some monitor's verdict; both constructs can be freely composed. We show how all operators of Linear Temporal Logic, as well as the parametric slicing of an input trace, can be written as Stream Logic constructs.
Causality in Message-Based Interface Contracts: A Temporal Logic "Whodunit"Sylvain Hallé
Interface contracts are sets of constraints specifying valid exchanges of messages between two or more peers. A contract violation occurs when one of the peers fails to fulfil one of these constraints and emits a message that is not a valid continuation of a message "trace". In some cases, the message that directly exposes the violation turns out to be the last of a succession of forced moves, while the "root cause" of the violation resides earlier in the trace and may emanate from a different peer. We formally define the notion of causality for interface contracts expressed in a first-order extension of Linear Temporal Logic. In particular, we show how the detection of root causes reduces to satisfiability solving of a precise set of formulæ. An experimental setup shows how causality can be analyzed automatically on a pre-recorded message trace.
Graph Methods for Generating Test Cases with Universal and Existential Constr...Sylvain Hallé
We introduce a generalization of the t -way test case generation problem, where parameter t is replaced by a set Φ of Boolean conditions on attribute values. We then present two reductions of this problem to graphs; first, to graph colouring, where we link the the minimal number of tests to the chromatic number of some graph; second, to hypergraph vertex covering. This latter formalization allows us to handle problems with constraints of two kinds: those that must be true for every generated test case, and those that must be true for at least one test case. Experimental results show that the proposed solution produces test suites of slightly smaller sizes than a range of existing tools, while being more general: to the best of our knowledge, our work is the first to allow existential constraints over test cases.
Chasing Bugs with the BeepBeep Event Stream ProcessorSylvain Hallé
Runtime verification is the process of observing a sequence of events generated by a running system and comparing it to some formal specification for potential violations. We show how the use of the BeepBeep event stream processor can greatly speed up the testing phase of a video game under development, by automating the detection of bugs when the game is being played. This process generalizes to a wide number of other use cases, including web application debugging and network intrusion detection.
A Case for "Piggyback" Runtime MonitoringSylvain Hallé
A runtime monitor enforcing a constraint on sequences of method calls on an object must keep track of the state of the sequence by updating an appropriate state machine. The present paper stems from the observation that an object's member fields must already contain an encoding of that state machine, and that a monitor essentially duplicates operations that the object performs internally. Rather than maintain a state machine in parallel, the paper puts forward the concept of "piggyback" runtime monitoring, where the monitor relies as much as possible on the object's own state variables to perform its task. Experiments on real-world benchmarks show that this approach greatly simplifies the monitoring process and drastically reduces the incurred runtime overhead compared to classical solutions.
Activity Recognition Through Complex Event Processing: First Findings Sylvain Hallé
The activities of daily living of a patient in a smart home environment can be detected to a large extent by the real-time analysis of characteristics of the habitat's electrical consumption. However, reasoning over the conduct of these activities occurs at a much higher level of abstraction than what the sensors generally produce. In this paper, we leverage the concept of Complex Event Processing (CEP), in which low-level data streams are progressively transformed into higher-level ones, to the task of activity recognition. We show how the use of an appropriate representation for each level of abstraction can greatly simplify the process. We also report on the use of an existing event stream processor to successfully implement the complete chain, from low-level sensor data up to a sequence of discrete and high-level actions.
Solving Equations on Words with Morphisms and AntimorphismsSylvain Hallé
Word equations are combinatorial equalities between strings of symbols, variables and functions, which can be used to model problems in a wide range of domains. While some complexity results for the solving of specific classes of equations are known, currently there does not exist a systematic equation solver. We present in this paper a reduction of the problem of solving word equations to Boolean satisfiability, and describe the implementation of a general-purpose tool that leverages existing SAT solvers for this purpose. Our solver will prove useful in the resolution of word equations, and in the computer-based exploration of various combinatorial conjectures.
Decentralized Enforcement of Artifact LifecyclesSylvain Hallé
Artifact-centric workflows describe possible executions of a business process through constraints expressed from the point of view of the documents exchanged between principals. A sequence of manipulations is deemed valid as long as every document in the workflow follows its prescribed lifecycle at all steps of the process. So far, establishing that a given workflow complies with artifact lifecycles has mostly been done through static verification, or by assuming a centralized access to all artifacts where these constraints can be monitored and enforced. We present in this paper an alternate method of enforcing document lifecycles that requires neither static verification nor single-point access. Rather, the document itself is designed to carry fragments of its history, protected from tampering using hashing and public-key encryption. Any principal involved in the process can verify at any time that a document’s history complies with a given lifecycle. Moreover, the proposed system also enforces access permissions: not all actions are visible to all principals, and one can only modify and verify what one is allowed to observe.
A formalization of complex event stream processingSylvain Hallé
Information systems in general, and business processes in particular, generate a wealth of information in the form of event traces or logs. The analysis of these logs, either offline or in real-time, can be put to numerous uses: computation of various statistics, detection of anomalous patterns or compliance violations of some form of contract. However, current solutions for Complex Event Processing (CEP) generally offer only a restricted set of predefined queries on traces, and otherwise require a user to write procedural code to compute custom queries. In this presentation, we present a formal and declarative language for the manipulation of event traces.
We describe work in progress on the design and implementation of an SQL-like language for performing complex queries on event streams. This language aims at providing a simple, intuitive and fully non-procedural syntax, while still preserving backwards compatibility with traditional SQL. The syntax and informal semantics of the language are introduced; multiple examples of scenarios taken from past literature are then presented, and used to compare the expressiveness and intuitiveness of the proposed language with respect to existing Complex Event Processing engines.
A Runtime Monitoring Framework for Event Streams with Non-Primitive ArgumentsSylvain Hallé
A runtime monitor is a tool that takes as input a model of some system, and observes in real time that the sequence of events produced by a run of that system follows the specification. While existing monitoring solutions generally use finite-state machines and temporal logic as their model language, the specification is ultimately tangled with hand-written, implementation-specific details which severely limit their range of application. We present a runtime monitoring platform that clearly separates the extraction of events in the running program from the specification and monitoring process. This separation allows one to cleanly monitor first-order properties involving arbitrarily complex native program objects, while still incurring reasonable overhead.
MapReduce for Parallel Trace Validation of LTL PropertiesSylvain Hallé
We present an algorithm for the automated verification of Linear Temporal Logic formulae on event traces using an increasingly popular cloud computing framework called MapReduce. The algorithm can process multiple, arbitrary fragments of the trace in parallel, and compute its final result through a cycle of runs of MapReduce instances. Compared to classical, single-instance solutions, a proof-of-concept implementation shows through experimental evaluation how the algorithm reduces by as much as 90% the number of operations that must be performed linearly, resulting in a commensurate speed gain.
This presentation is an introduction to Complex Event Processing (CEP) intended for an practicioners of Runtime Verification. It first describes typical CEP problems, popular tools and their query languages. It then presents BeepBeep 3, an event stream processor that attempts to bridge the gap between RV and CEP. Thanks to BeepBeep’s generic architecture and flexible input language, queries and properties from both fields can be efficiently processed.
Testing Web Applications Through User Interface Constraints (CASCON 2015 Talk)Sylvain Hallé
We shall explore the concept of web application testing through the verification of declarative constraints on the contents of its user interface --that is, DOM, CSS and behavioural properties. It turns out that a lot of non GUI (e.g. functional, security) problems can also be verified by observing the application's GUI.
Intersud, rencontre B2B inversée le 6 septembre 2016CibleWeb
Le 6 septembre au Stade de la Méditerranée à Béziers
Participez aux premières rencontres industrielles de la grande Région,
Accélérez votre business !
Le 6 septembre au stade de la Méditerranée, profitez des opportunités industrielles offertes par la grande région : Intersud, ce sont des rencontres B2B dédiées aux donneurs d’ordres, sous-traitants et prestataires technologiques en Languedoc-Roussillon-Midi-Pyrénées.
Grâce à une étude précise des besoins et des savoir-faire identifiés, Intersud garantit des contacts qualifiés pour le développement de nouveaux courants d’affaires.
http://www.intersud.biz/
Inscription : http://intersud.prollision.eu/
Monitoring Business Process Compliance Across Multiple Executions with Stream...Sylvain Hallé
Slides of a talk given at EDOC 2023, November 3rd, 2023.
Abstract: Compliance checking is the operation that consists of assessing whether every execution trace of a business process satisfies a given correctness condition. The paper introduces the notion of hyperquery, which is a calculation that involves multiple traces from a log at the same time. A particular case of hyperquery is a hypercompliance condition, which is a correctness requirement that involves the whole log instead of individual process instances. A formalization of hyperqueries is presented, along with a number of elementary operations to express hyperqueries on arbitrary logs. An implementation of these concepts in an event stream processing engine allows users to concretely evaluate hyperqueries in real time.
A Stream-Based Approach to Intrusion DetectionSylvain Hallé
Slides of a presentation given to promote the book "CyberSecurity in a DevOps Environment" (2023).
Abstract:
Integrating security in the development and operation of information systems is the cornerstone of SecDevOps. From an operational perspective, one of the key activities for achieving such an integration is the detection of incidents (such as intrusions), especially in an automated manner. However, one of the stumbling blocks of an automated approach to intrusion detection is the management of the large volume of information typically produced by this type of solution. Existing works on the topic have concentrated on the reduction of volume by increasing the precision of the detection approach, thus lowering the rate of false alarms. However, another, less explored possibility is to reduce the volume of evidence gathered for each alarm raised.
This chapter explores the concept of intrusion detection from the angle of complex event processing. It provides a formalization of the notion of pattern matching in a sequence of events produced by an arbitrary system, by framing the task as a runtime monitoring problem. It then focuses on the topic of incident reporting, and proposes a technique to automatically extract relevant elements of a stream that explain the occurrence of an intrusion. These relevant elements generally amount to a small fraction of all the data ingested for an alarm to be triggered, and thus help reduce the volume of evidence that needs to be examined by manual means. The approach is experimentally evaluated on a proof-of-concept implementation of these principles.
Solving Equations on Words with Morphisms and AntimorphismsSylvain Hallé
Word equations are combinatorial equalities between strings of symbols, variables and functions, which can be used to model problems in a wide range of domains. While some complexity results for the solving of specific classes of equations are known, currently there does not exist a systematic equation solver. We present in this paper a reduction of the problem of solving word equations to Boolean satisfiability, and describe the implementation of a general-purpose tool that leverages existing SAT solvers for this purpose. Our solver will prove useful in the resolution of word equations, and in the computer-based exploration of various combinatorial conjectures.
Decentralized Enforcement of Artifact LifecyclesSylvain Hallé
Artifact-centric workflows describe possible executions of a business process through constraints expressed from the point of view of the documents exchanged between principals. A sequence of manipulations is deemed valid as long as every document in the workflow follows its prescribed lifecycle at all steps of the process. So far, establishing that a given workflow complies with artifact lifecycles has mostly been done through static verification, or by assuming a centralized access to all artifacts where these constraints can be monitored and enforced. We present in this paper an alternate method of enforcing document lifecycles that requires neither static verification nor single-point access. Rather, the document itself is designed to carry fragments of its history, protected from tampering using hashing and public-key encryption. Any principal involved in the process can verify at any time that a document’s history complies with a given lifecycle. Moreover, the proposed system also enforces access permissions: not all actions are visible to all principals, and one can only modify and verify what one is allowed to observe.
A formalization of complex event stream processingSylvain Hallé
Information systems in general, and business processes in particular, generate a wealth of information in the form of event traces or logs. The analysis of these logs, either offline or in real-time, can be put to numerous uses: computation of various statistics, detection of anomalous patterns or compliance violations of some form of contract. However, current solutions for Complex Event Processing (CEP) generally offer only a restricted set of predefined queries on traces, and otherwise require a user to write procedural code to compute custom queries. In this presentation, we present a formal and declarative language for the manipulation of event traces.
We describe work in progress on the design and implementation of an SQL-like language for performing complex queries on event streams. This language aims at providing a simple, intuitive and fully non-procedural syntax, while still preserving backwards compatibility with traditional SQL. The syntax and informal semantics of the language are introduced; multiple examples of scenarios taken from past literature are then presented, and used to compare the expressiveness and intuitiveness of the proposed language with respect to existing Complex Event Processing engines.
A Runtime Monitoring Framework for Event Streams with Non-Primitive ArgumentsSylvain Hallé
A runtime monitor is a tool that takes as input a model of some system, and observes in real time that the sequence of events produced by a run of that system follows the specification. While existing monitoring solutions generally use finite-state machines and temporal logic as their model language, the specification is ultimately tangled with hand-written, implementation-specific details which severely limit their range of application. We present a runtime monitoring platform that clearly separates the extraction of events in the running program from the specification and monitoring process. This separation allows one to cleanly monitor first-order properties involving arbitrarily complex native program objects, while still incurring reasonable overhead.
MapReduce for Parallel Trace Validation of LTL PropertiesSylvain Hallé
We present an algorithm for the automated verification of Linear Temporal Logic formulae on event traces using an increasingly popular cloud computing framework called MapReduce. The algorithm can process multiple, arbitrary fragments of the trace in parallel, and compute its final result through a cycle of runs of MapReduce instances. Compared to classical, single-instance solutions, a proof-of-concept implementation shows through experimental evaluation how the algorithm reduces by as much as 90% the number of operations that must be performed linearly, resulting in a commensurate speed gain.
This presentation is an introduction to Complex Event Processing (CEP) intended for an practicioners of Runtime Verification. It first describes typical CEP problems, popular tools and their query languages. It then presents BeepBeep 3, an event stream processor that attempts to bridge the gap between RV and CEP. Thanks to BeepBeep’s generic architecture and flexible input language, queries and properties from both fields can be efficiently processed.
Testing Web Applications Through User Interface Constraints (CASCON 2015 Talk)Sylvain Hallé
We shall explore the concept of web application testing through the verification of declarative constraints on the contents of its user interface --that is, DOM, CSS and behavioural properties. It turns out that a lot of non GUI (e.g. functional, security) problems can also be verified by observing the application's GUI.
Intersud, rencontre B2B inversée le 6 septembre 2016CibleWeb
Le 6 septembre au Stade de la Méditerranée à Béziers
Participez aux premières rencontres industrielles de la grande Région,
Accélérez votre business !
Le 6 septembre au stade de la Méditerranée, profitez des opportunités industrielles offertes par la grande région : Intersud, ce sont des rencontres B2B dédiées aux donneurs d’ordres, sous-traitants et prestataires technologiques en Languedoc-Roussillon-Midi-Pyrénées.
Grâce à une étude précise des besoins et des savoir-faire identifiés, Intersud garantit des contacts qualifiés pour le développement de nouveaux courants d’affaires.
http://www.intersud.biz/
Inscription : http://intersud.prollision.eu/
Monitoring Business Process Compliance Across Multiple Executions with Stream...Sylvain Hallé
Slides of a talk given at EDOC 2023, November 3rd, 2023.
Abstract: Compliance checking is the operation that consists of assessing whether every execution trace of a business process satisfies a given correctness condition. The paper introduces the notion of hyperquery, which is a calculation that involves multiple traces from a log at the same time. A particular case of hyperquery is a hypercompliance condition, which is a correctness requirement that involves the whole log instead of individual process instances. A formalization of hyperqueries is presented, along with a number of elementary operations to express hyperqueries on arbitrary logs. An implementation of these concepts in an event stream processing engine allows users to concretely evaluate hyperqueries in real time.
A Stream-Based Approach to Intrusion DetectionSylvain Hallé
Slides of a presentation given to promote the book "CyberSecurity in a DevOps Environment" (2023).
Abstract:
Integrating security in the development and operation of information systems is the cornerstone of SecDevOps. From an operational perspective, one of the key activities for achieving such an integration is the detection of incidents (such as intrusions), especially in an automated manner. However, one of the stumbling blocks of an automated approach to intrusion detection is the management of the large volume of information typically produced by this type of solution. Existing works on the topic have concentrated on the reduction of volume by increasing the precision of the detection approach, thus lowering the rate of false alarms. However, another, less explored possibility is to reduce the volume of evidence gathered for each alarm raised.
This chapter explores the concept of intrusion detection from the angle of complex event processing. It provides a formalization of the notion of pattern matching in a sequence of events produced by an arbitrary system, by framing the task as a runtime monitoring problem. It then focuses on the topic of incident reporting, and proposes a technique to automatically extract relevant elements of a stream that explain the occurrence of an intrusion. These relevant elements generally amount to a small fraction of all the data ingested for an alarm to be triggered, and thus help reduce the volume of evidence that needs to be examined by manual means. The approach is experimentally evaluated on a proof-of-concept implementation of these principles.
Event Stream Processing with BeepBeep 3Sylvain Hallé
Event logs and event streams can be found in software systems of very diverse kinds. Analyzing the wealth of information contained in these logs can serve multiple purposes. In this tutorial, the audience will learn about BeepBeep, a versatile Java library intended to make the processing of event streams (either offline or in realtime) both fun and simple. BeepBeep is the result of more than a decade of research led by a team at Laboratoire d’informatique formelle at Université du Québec à Chicoutimi (Canada). Over the past few years, BeepBeep has been involved in a variety of case studies, and provides built-in support for writing domain-specific languages. Recently, a complete textbook has been published on BeepBeep, testifying to the maturity that the system has acquired.
Smart Contracts-Enabled Simulation for Hyperconnected LogisticsSylvain Hallé
(Slides for a talk given in the journal-first track of the EDOC 2022 conference.)
The combination of the Internet of Things and blockchain-based technologies represents a real opportunity for supply chain and logistics protagonists, who need more dynamic, trustworthy and transparent tracking systems in order to improve their efficiency and strengthen customer confidence. In parallel, hyperconnected logistics promise more efficient and sustainable goods handling and delivery. This chapter shows how the Ethereum blockchain and smart contracts can be used to implement a shareable and secured tracking system for hyperconnected logistics. A simulation using the well-known AnyLogic software tool provides insights on the monitoring of properties depicting shipment lifecycle constraints through a stream of blockchain log events processed by BeepBeep 3, an open source stream processing engine.
Test Suite Generation for Boolean Conditions with Equivalence Class PartitioningSylvain Hallé
Boolean test input generation is the process of finding sets of values for variables of a logical expression such that a given coverage criterion is achieved. This paper presents a formal framework in which evaluating an expression produces a tree structure, and where a coverage criterion is expressed as equivalence classes induced by a particular transformation over these trees. It then defines many well-known coverage criteria as particular cases of this framework. The paper describes an algorithm to generate test suites by a reduction through a graph problem; this algorithm works in the same way regardless of the criterion considered. An experimental evaluation of this technique shows that it produces test suites that are in many cases smaller than existing tools.
Synthia: a Generic and Flexible Data Structure Generator (Long Version)Sylvain Hallé
Synthia is a versatile, modular and extensible Java-based data structure generation library. It is centered on the notion of "pickers", which are objects producing values of a given type on demand. Pickers are stateful and can be given as input to other pickers; this chaining principle can generate objects whose structure follows a complex pattern. The paper describes the core principles and key features of the library, including test input shrinking, provenance tracking, and object mutation.
Test Sequence Generation with Cayley Graphs (Talk @ A-MOST 2021)Sylvain Hallé
The paper presents a theoretical foundation for test sequence generation based on an input specification. The set of possible test sequences is first partitioned according to a generic "triaging" function, which can be created from a state-machine specification in various ways. The notion of coverage metric is then expressed in terms of the categories produced by this function. Many existing test generation problems, such as t-way state or transition coverage, become particular cases of this generic framework. We then present algorithms for generating sets of test sequences providing guaranteed full coverage with respect to a metric, by building and processing a special type of graph called a Cayley graph. An implementation of these concepts is then experimentally evaluated against existing techniques, and shows it provides better performance in terms of running time and test suite size.
Efficient Offline Monitoring of LTL with Bit Vectors (Talk at SAC 2021)Sylvain Hallé
We describe an extension of the BeepBeep stream processing library for the offline verification of arbitrary expressions of Linear Temporal Logic using bitmap manipulations. Experimental results show that, for complex LTL formulæ containing up to 20 operators, event traces can be evaluated at a throughput of millions of events per second and provide a considerable speed-up compared to the current implementation of the tool.
Detecting Responsive Web Design Bugs with Declarative SpecificationsSylvain Hallé
Responsive Web Design (RWD) is a concept that is born from the need to provide users with a positive and intuitive experience, no matter what device they use. Complex Cascading Style Sheets (CSS) are used in RWD to smoothly change the appearance of a website based on the window width of the device being used. The paper presents an automated approach for testing these dynamic web applications, where a combination of dynamic crawling and back-end testing is used to automatically detect RWD bugs.
Streamlining the Inclusion of Computer Experiments in Research PapersSylvain Hallé
To run experiments on a computer, you probably write command-line scripts for various tasks: generate your data, save it into files, process and display them as plots or tables to include in a paper. But soon enough, your handful of “quick and dirty” files becomes a bunch of poorly documented scripts that generate and pass around all kinds of obscure temporary files. LabPal is a library that allows you to set up an environment for running experiments, collating their results and processing them.
Writing Domain-Specific Languages for BeepBeepSylvain Hallé
This paper describes a plug-in extension of the BeepBeep 3 event stream processing engine. The extension allows one to write a custom grammar defining a particular specification language on event traces. A built-in interpreter can then convert expressions of the language into chains of BeepBeep processors through just a few lines of code, making it easy for users to create their own domain-specific languages.
Real-Time Data Mining for Event StreamsSylvain Hallé
Information systems produce different types of event logs; in many situations, it may be desirable to look for trends inside these logs. We show how trends of various kinds can be computed over such logs in real time, using a generic framework called the trend distance workflow. Many common computations on event streams turn out to be special cases of this workflow, depending on how a handful of workflow parameters are defined. This process has been implemented and tested in a real-world event stream processing tool, called BeepBeep.
Technologies intelligentes d'aide au développement d'applications web (WAQ 2018)Sylvain Hallé
Surfez sur le web quelques heures, et vous trouverez sûrement un site ou une application qui contient un bogue dans son interface graphique. Que ce soit un bouton qui ne fonctionne pas, un rectangle partiellement caché ou mal positionné, il semble que les problèmes d’interface soient notoirement difficiles à traquer! Des technologies intelligentes pourraient-elles aider les concepteurs et les développeurs à mieux tester leurs interfaces? Au Laboratoire d’informatique formelle de l’Université du Québec à Chicoutimi, nous le croyons. Nous avons développé Cornipickle, un logiciel permettant à un développeur d’énoncer, dans un langage simple et lisible, une foule de contraintes sur le positionnement et le contenu des éléments d’une interface web. Nous verrons comment Cornipickle peut s’intégrer à une application existante, détecter des problèmes, identifier les éléments qui sont fautifs et même suggérer des correctifs. Ceci permet donc à un développeur de gagner beaucoup de temps lors de la recherche des problèmes.
A "Do-It-Yourself" Specification Language with BeepBeep 3 (Talk @ Dagstuhl 2017)Sylvain Hallé
This talk reviews the basic principles behind the BeepBeep 3 event stream processing engine, and the facilities it provides to help you design you own, domain-specific query language.
Event Stream Processing with Multiple ThreadsSylvain Hallé
We present an extension to the BeepBeep 3 event stream engine that allows the use of multiple threads during the evaluation of a query. Compared to the single-threaded version of BeepBeep, the allocation of just a few threads to specific portions of a query provides improvement in terms of throughput.
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98. 1 2 6
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Coloriage
homomorphisme de graphe (n. m.)
Si G et H sont deux graphes dont on note les sommets V(G) et V(H)
et les arêtes E(G) et E(H), une application f: V(G) → V(H) qui envoie
les sommets de G sur ceux d H est un morphisme de graphes si:
∀(u,v) ∊ E(G), (f(u),f(v)) ∊ E(H). Plus sih plement, f est un morphisme
de graphes si l'image de e arête de G est une arête de H. S'il y a
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129. COVERSTO Y
Verified software
My computer won’t fail me
Web-browser crashes are annoyinc but as far as software malfunctions go, the
consequence are mild. With a plane’s autopilot or the control room of a nuclear power
station, it’s another matter. As our lives become ever more saturated with computers,
how can we know they won’t fail? Currently, we systematically test all conceivable
scenarios un er which they might. A better insurance might be logic. [...]
32 | New Scientist | 16 October 2010
130. COVERSTO Y
Verified software
My computer won’t fail me
Web-browser crashes are annoyinc but as far as software malfunctions go, the
consequence are mild. With a plane’s autopilot or the control room of a nuclear power
station, it’s another matter. As our lives become ever more saturated with computers,
how can we know they won’t fail? Currently, we systematically test all conceivable
scenarios un er which they might. A better insurance might be logic. [...]
32 | New Scientist | 16 October 2010