Eddie Lima | Universidade Federal do Amazonas (original) (raw)

Papers by Eddie Lima

It contains the codes and benchmarks for reproducing the experiments of the paper entitled "... more It contains the codes and benchmarks for reproducing the experiments of the paper entitled "Formal Synthesis of Non-fragile State-Feedback Digital Controllers Considering Performance Requirements for Step Response".

Artificial Neural Networks (ANNs) are being deployed for an increasing number of safety-critical ... more Artificial Neural Networks (ANNs) are being deployed for an increasing number of safety-critical applications, including autonomous cars and medical diagnosis. However, concerns about their reliability have been raised due to their black-box nature and apparent fragility to adversarial attacks. These concerns are amplified when ANNs are deployed on the restricted systems, which limits the precision of mathematical operations and thus introduce additional quantization errors. Here, we develop and evaluate a novel symbolic verification framework using software model checking (SMC) and satisfiability modulo theories (SMT) to check for vulnerabilities in ANNs. More specifically, we propose several ANN-related optimizations for SMC, including invariant inference via interval analysis, slicing, expression simplifications, and discretization of non-linear activation functions. With this verification framework, we can provide formal guarantees on the safe behavior of ANNs implemented both i...

2007 IEEE International Conference on Communications, 2007

Abstract Mobile wireless broadband access networks are now becoming a reality, thanks to the emer... more Abstract Mobile wireless broadband access networks are now becoming a reality, thanks to the emerging IEEE 802.16 e standard. This kind of network offers different challenges when compared to the fixed ones, as power consumption becomes a major concern. In this ...

arXiv (Cornell University), Nov 24, 2021

QNNVerifier is the first open-source tool for verifying implementations of neural networks that t... more QNNVerifier is the first open-source tool for verifying implementations of neural networks that takes into account the finite word-length (i.e. quantization) of their operands. The novel support for quantization is achieved by employing state-of-the-art software model checking (SMC) techniques. It translates the implementation of neural networks to a decidable fragment of first-order logic based on satisfiability modulo theories (SMT). The effects of fixed-and floatingpoint operations are represented through direct implementations given a hardware-determined precision. Furthermore, QNNVerifier allows to specify bespoke safety properties and verify the resulting model with different verification strategies (incremental and k-induction) and SMT solvers. Finally, QNNVerifier is the first tool that combines invariant inference via interval analysis and discretization of non-linear activation functions to speed up the verification of neural networks by orders of magnitude. A video presentation of QNNVerifier is available at https://youtu.be/7jMgOL41zTY. CCS Concepts: • Computing methodologies → Neural networks; • Software and its engineering → Formal software verification.

... Academic Staff; International Doctoral Candidates; Guests; Press. Lupe: University from A - Z... more ... Academic Staff; International Doctoral Candidates; Guests; Press. Lupe: University from A - Z; Staff and Departments Search; Course Catalog (in German); ... Razon S, Basevitch I, Filho E, Land WM, Thompson B, Tenenbaum G (2010) In: Greenville, South Carolina. ...

2021 IEEE International Conference on Consumer Electronics (ICCE)

Field problems are usual in digital TV (DTV) systems due to development errors and wrongly perfor... more Field problems are usual in digital TV (DTV) systems due to development errors and wrongly performed configuration. DTV receivers evolve with new models, which usually leads to increasingly correct devices; however, configuration errors always occur due to new head-ends and equipment, which often cause signal non-conformance and receiver malfunction. This work addresses the mentioned problem and proposes a methodology for automated signal analysis that can be used for both preventive and report-driven evaluation procedures, also leading to reduced losses. A real implementation of it showed its efficiency and efficacy, with analysis procedures that can even be five times faster.

2019 IEEE International Conference on Consumer Electronics (ICCE)

Digital TV (DTV) receivers are central devices in traditional Brazilian homes, which provide info... more Digital TV (DTV) receivers are central devices in traditional Brazilian homes, which provide information and entertainment for families. Nonetheless, despite great availability of content options, only one DTV program can be presented, at a time, which is a very limiting feature. The present article addresses such a problem and proposes a receiver architecture capable of presenting two TV programs, either using the same display or auxiliary devices, such as smart phones and tablets. A prototype implementing the proposed architecture was developed, which showed its effectiveness and feasibility.

Electronics

This paper presents a new hardware reconfiguration approach named hardware reconfiguration throug... more This paper presents a new hardware reconfiguration approach named hardware reconfiguration through digital television (HARD), which can update FPGA hardware modules based on digital TV (DTV) signals. Such a scheme allows several synthesized hardware cores (bitstreams) signaled and broadcast through open DTV signals via data streaming to be identified, acquired, decoded, and then used for system updates. Reconfiguration data are partitioned, encapsulated into private sections, and then sent in a carrousel fashion in order to be recovered by modified receivers. Service information content, specially designed for identifying and describing the characteristics of multiplexed hardware bitstreams, was added to the transmitted signal and provided all necessary information in the traditional DTV style. The receiver framework, in turn, checked whether those characteristics corresponded to its embedded reconfigurable devices and, if a match was found, it reassembled the related bitstreams and...

2021 IEEE International Conference on Consumer Electronics (ICCE)

Field testing is crucial for the deployment of digital TV receivers, as it assures that the latte... more Field testing is crucial for the deployment of digital TV receivers, as it assures that the latter can operate under real conditions provided by digital TV networks. Usually, field-testing procedures are manually performed, which often leads to long execution times and wrong measures and conclusions. The present work addresses this problem and proposes a methodology for automatic field-testing procedures, which does not require trained professionals and provides reliable results. Experiments with an implementation based on it showed its efficacy and efficiency, with testing procedures that are, in average, 13.7 times faster than manual ones.


The SM-MMP (Side-Match Multidimensional Mul- tiscale Parser) is a method based on approximate mul... more The SM-MMP (Side-Match Multidimensional Mul- tiscale Parser) is a method based on approximate multiscale pattern matching, where the dictionary is built considering smoothness constraints around block boundaries, which results in a better performance for smooth images. In this work, a generalized framework is presented, in which the match attempt with neighboring blocks is performed in a hierarquical way and with a greater degree of restriction. The SM-MMP can be considered as a particular case of this new approach. Besides, a new dictionary usage strategy is presented, which employs elements from the causal neighborhood of the block being encoded. The simulations performed on grayscale images show that the proposed framework is effective, presenting a superior performance when comparing to its predecessor.

2020 IEEE International Conference on Consumer Electronics - Taiwan (ICCE-Taiwan), 2020

In production lines for monitors and displays, some validation tests are based on visual inspecti... more In production lines for monitors and displays, some validation tests are based on visual inspection, whose preliminary step usually consists in detecting the area corresponding to a monitor's screen, which is then followed by evaluation procedures. Nonetheless, depending on the chosen technique, such a detection may consume much of a given test's total time. The present paper addresses the mentioned problem and presents an approach that uses semantic segmentation and convolutional neural networks for screen segmentation, which allows a reduction on elapsed test times about 27.77%, without compromising the accuracy already obtained with traditional approaches.

We integrate a simplified model of the Qt framework, named as Qt operational model (QtOM), into t... more We integrate a simplified model of the Qt framework, named as Qt operational model (QtOM), into the efficient SMT-based contextbounded model checker (ESBMC++), which results in ESBMC . In particular, ESBMC is a bounded model checking tool to verify Qtbased applications, which focuses on the verification of code properties, such as invalid memory access and containers usage, through preand postconditions, data usage evaluation, and simulation features. Experimental results show that ESBMC can be effectively and efficiently applied to verify Qt-based consumer electronics applications.

Currently, the Brazilian digital television system is migrating its middleware approach from prof... more Currently, the Brazilian digital television system is migrating its middleware approach from profile Ginga-C to an integrated broadcast-broadband (IBB) strategy, known as profile Ginga-D. Nonetheless, there is no indication regarding how to implement the new IBB services, while maintaining compatibility with older features. The present work proposes a methodology able to extending current implementations, in a systematic way, with the goal of harmonization maintenance among modules and conformance regarding current standards.

2019 IEEE International Conference on Consumer Electronics (ICCE), 2019

Interconnection among consumer electronics products is of paramount importance, mainly due to the... more Interconnection among consumer electronics products is of paramount importance, mainly due to the advent of home networks and a myriad of devices and services. In addition, when video is involved, which is common in most homes, wide bandwidth is necessary, due to content resolution. In that sense, an interesting approach is to provide connection through light links, whose spectrum is unregulated and presents abundant bandwidth. The present article addresses such a problem and proposes an infrared-light-based architecture for transmission of multimedia content in consumer electronics environments. The obtained initial results showed its effectiveness, with transmission distances exceeding 5m.

ArXiv, 2015

The software development process for embedded systems is getting faster and faster, which general... more The software development process for embedded systems is getting faster and faster, which generally incurs an increase in the associated complexity. As a consequence, consumer electronics companies usually invest a lot of resources in fast and automatic verification processes, in order to create robust systems and reduce product recall rates. Because of that, the present paper proposes a simplified version of the Qt framework, which is integrated into the Efficient SMT-Based Bounded Model Checking tool to verify actual applications that use the mentioned framework. The method proposed in this paper presents a success rate of 94.45%, for the developed test suite.

2020 IEEE International Conference on Consumer Electronics (ICCE)

Ginga is a middleware specified to offer support to execution of interactive applications, on dig... more Ginga is a middleware specified to offer support to execution of interactive applications, on digital TV (DTV) receivers. Although it offers an extensive application programming interface (API), it does not provide integration with IoT devices, which would favor its use in Internet of things (IoT) environments. This work aims to integrate Ginga with the IoT technology, through support to the message queuing telemetry transport (MQTT) communication protocol. Ginga’s API has been extended with support to MQTT, which resulted in an integrated framework regarding IoT and DTV. As a result, reference applications were developed, in order to validate the proposed framework, in a home network.

Recently, the middleware Ginga, which was developed for the Brazilian digital television system (... more Recently, the middleware Ginga, which was developed for the Brazilian digital television system (SBTVD), was updated. It is now called DTV Play and presents features related to the integrated broadcast-broadband paradigm, including execution of hypertext markup language version 5 (HTML5) applications and encrypted-content handling. However, such novelties require deeper integration with platforms, which already exists for native HTML5 engines. This work proposes a methodology for implementing those features through HTML5 engines, aiming at reducing development time and providing a simpler framework for SBTVD receivers. This approach is currently being implemented and has already proved its efficacy and efficiency.

Proceedings of the 26th ACM SIGSOFT International Symposium on Software Testing and Analysis

A MATLAB toolbox is presented, with the goal of checking occurrences of design errors typically f... more A MATLAB toolbox is presented, with the goal of checking occurrences of design errors typically found in fixed-point digital systems, considering finite word-length effects. In particular, the present toolbox works as a front-end to a recently introduced verification tool, known as Digital-System Verifier, and checks overflow, limit cycle, quantization, stability, and minimum phase errors, in digital systems represented by transfer-function and state-space equations. It provides a command-line version, with simplified access to specific functions, and a graphical-user interface, which was developed as a MATLAB application. The resulting toolbox is important for the verification community, since it shows the applicability of verification to real-world systems.

Lecture Notes in Computer Science

This paper presents optimization through counterexamples (OptCE), which is a verification tool de... more This paper presents optimization through counterexamples (OptCE), which is a verification tool developed for optimizing target functions. In particular, OptCE employs bounded model checking techniques based on boolean satisfiability and satisfiability modulo theories, which are able to obtain global minima of convex and non-convex functions. OptCE is implemented in C/C++, performs all optimization steps automatically, and iteratively analyzes counterexamples, in order to inductively achieve global optimization based on a verification oracle. Experimental results show that OptCE can effectively find optimal solutions for all evaluated benchmarks, while traditional techniques are usually trapped by local minima.

Anais de XXXVII Simpósio Brasileiro de Telecomunicações e Processamento de Sinais

Resumo-Sinais de eletrocardiograma (ECG) podem ser utilizados tanto para acompanhamento quanto di... more Resumo-Sinais de eletrocardiograma (ECG) podem ser utilizados tanto para acompanhamento quanto diagnóstico de doenças cardíacas, o que depende de infraestruturas de armazenamento e transmissão. Entretanto, como memória e banda de transmissão são recursos finitos, torna-se necessário comprimir dados de ECG. Além disso, com relação ao monitoramentoà distância, espera-se que o hardware utilizado seja simples e barato. O presente trabalho ataca o problema mencionado e propõe uma nova metodologia de compressão de sinais de ECG, onde experimentos com uma implementação desse paradigma mostraram que tal abordagemé possível e também eficaz, desde que alinhadaàs condições de cada caso específico.

It contains the codes and benchmarks for reproducing the experiments of the paper entitled "... more It contains the codes and benchmarks for reproducing the experiments of the paper entitled "Formal Synthesis of Non-fragile State-Feedback Digital Controllers Considering Performance Requirements for Step Response".

Artificial Neural Networks (ANNs) are being deployed for an increasing number of safety-critical ... more Artificial Neural Networks (ANNs) are being deployed for an increasing number of safety-critical applications, including autonomous cars and medical diagnosis. However, concerns about their reliability have been raised due to their black-box nature and apparent fragility to adversarial attacks. These concerns are amplified when ANNs are deployed on the restricted systems, which limits the precision of mathematical operations and thus introduce additional quantization errors. Here, we develop and evaluate a novel symbolic verification framework using software model checking (SMC) and satisfiability modulo theories (SMT) to check for vulnerabilities in ANNs. More specifically, we propose several ANN-related optimizations for SMC, including invariant inference via interval analysis, slicing, expression simplifications, and discretization of non-linear activation functions. With this verification framework, we can provide formal guarantees on the safe behavior of ANNs implemented both i...

2007 IEEE International Conference on Communications, 2007

Abstract Mobile wireless broadband access networks are now becoming a reality, thanks to the emer... more Abstract Mobile wireless broadband access networks are now becoming a reality, thanks to the emerging IEEE 802.16 e standard. This kind of network offers different challenges when compared to the fixed ones, as power consumption becomes a major concern. In this ...

arXiv (Cornell University), Nov 24, 2021

QNNVerifier is the first open-source tool for verifying implementations of neural networks that t... more QNNVerifier is the first open-source tool for verifying implementations of neural networks that takes into account the finite word-length (i.e. quantization) of their operands. The novel support for quantization is achieved by employing state-of-the-art software model checking (SMC) techniques. It translates the implementation of neural networks to a decidable fragment of first-order logic based on satisfiability modulo theories (SMT). The effects of fixed-and floatingpoint operations are represented through direct implementations given a hardware-determined precision. Furthermore, QNNVerifier allows to specify bespoke safety properties and verify the resulting model with different verification strategies (incremental and k-induction) and SMT solvers. Finally, QNNVerifier is the first tool that combines invariant inference via interval analysis and discretization of non-linear activation functions to speed up the verification of neural networks by orders of magnitude. A video presentation of QNNVerifier is available at https://youtu.be/7jMgOL41zTY. CCS Concepts: • Computing methodologies → Neural networks; • Software and its engineering → Formal software verification.

... Academic Staff; International Doctoral Candidates; Guests; Press. Lupe: University from A - Z... more ... Academic Staff; International Doctoral Candidates; Guests; Press. Lupe: University from A - Z; Staff and Departments Search; Course Catalog (in German); ... Razon S, Basevitch I, Filho E, Land WM, Thompson B, Tenenbaum G (2010) In: Greenville, South Carolina. ...

2021 IEEE International Conference on Consumer Electronics (ICCE)

Field problems are usual in digital TV (DTV) systems due to development errors and wrongly perfor... more Field problems are usual in digital TV (DTV) systems due to development errors and wrongly performed configuration. DTV receivers evolve with new models, which usually leads to increasingly correct devices; however, configuration errors always occur due to new head-ends and equipment, which often cause signal non-conformance and receiver malfunction. This work addresses the mentioned problem and proposes a methodology for automated signal analysis that can be used for both preventive and report-driven evaluation procedures, also leading to reduced losses. A real implementation of it showed its efficiency and efficacy, with analysis procedures that can even be five times faster.

2019 IEEE International Conference on Consumer Electronics (ICCE)

Digital TV (DTV) receivers are central devices in traditional Brazilian homes, which provide info... more Digital TV (DTV) receivers are central devices in traditional Brazilian homes, which provide information and entertainment for families. Nonetheless, despite great availability of content options, only one DTV program can be presented, at a time, which is a very limiting feature. The present article addresses such a problem and proposes a receiver architecture capable of presenting two TV programs, either using the same display or auxiliary devices, such as smart phones and tablets. A prototype implementing the proposed architecture was developed, which showed its effectiveness and feasibility.

Electronics

This paper presents a new hardware reconfiguration approach named hardware reconfiguration throug... more This paper presents a new hardware reconfiguration approach named hardware reconfiguration through digital television (HARD), which can update FPGA hardware modules based on digital TV (DTV) signals. Such a scheme allows several synthesized hardware cores (bitstreams) signaled and broadcast through open DTV signals via data streaming to be identified, acquired, decoded, and then used for system updates. Reconfiguration data are partitioned, encapsulated into private sections, and then sent in a carrousel fashion in order to be recovered by modified receivers. Service information content, specially designed for identifying and describing the characteristics of multiplexed hardware bitstreams, was added to the transmitted signal and provided all necessary information in the traditional DTV style. The receiver framework, in turn, checked whether those characteristics corresponded to its embedded reconfigurable devices and, if a match was found, it reassembled the related bitstreams and...

2021 IEEE International Conference on Consumer Electronics (ICCE)

Field testing is crucial for the deployment of digital TV receivers, as it assures that the latte... more Field testing is crucial for the deployment of digital TV receivers, as it assures that the latter can operate under real conditions provided by digital TV networks. Usually, field-testing procedures are manually performed, which often leads to long execution times and wrong measures and conclusions. The present work addresses this problem and proposes a methodology for automatic field-testing procedures, which does not require trained professionals and provides reliable results. Experiments with an implementation based on it showed its efficacy and efficiency, with testing procedures that are, in average, 13.7 times faster than manual ones.


The SM-MMP (Side-Match Multidimensional Mul- tiscale Parser) is a method based on approximate mul... more The SM-MMP (Side-Match Multidimensional Mul- tiscale Parser) is a method based on approximate multiscale pattern matching, where the dictionary is built considering smoothness constraints around block boundaries, which results in a better performance for smooth images. In this work, a generalized framework is presented, in which the match attempt with neighboring blocks is performed in a hierarquical way and with a greater degree of restriction. The SM-MMP can be considered as a particular case of this new approach. Besides, a new dictionary usage strategy is presented, which employs elements from the causal neighborhood of the block being encoded. The simulations performed on grayscale images show that the proposed framework is effective, presenting a superior performance when comparing to its predecessor.

2020 IEEE International Conference on Consumer Electronics - Taiwan (ICCE-Taiwan), 2020

In production lines for monitors and displays, some validation tests are based on visual inspecti... more In production lines for monitors and displays, some validation tests are based on visual inspection, whose preliminary step usually consists in detecting the area corresponding to a monitor's screen, which is then followed by evaluation procedures. Nonetheless, depending on the chosen technique, such a detection may consume much of a given test's total time. The present paper addresses the mentioned problem and presents an approach that uses semantic segmentation and convolutional neural networks for screen segmentation, which allows a reduction on elapsed test times about 27.77%, without compromising the accuracy already obtained with traditional approaches.

We integrate a simplified model of the Qt framework, named as Qt operational model (QtOM), into t... more We integrate a simplified model of the Qt framework, named as Qt operational model (QtOM), into the efficient SMT-based contextbounded model checker (ESBMC++), which results in ESBMC . In particular, ESBMC is a bounded model checking tool to verify Qtbased applications, which focuses on the verification of code properties, such as invalid memory access and containers usage, through preand postconditions, data usage evaluation, and simulation features. Experimental results show that ESBMC can be effectively and efficiently applied to verify Qt-based consumer electronics applications.

Currently, the Brazilian digital television system is migrating its middleware approach from prof... more Currently, the Brazilian digital television system is migrating its middleware approach from profile Ginga-C to an integrated broadcast-broadband (IBB) strategy, known as profile Ginga-D. Nonetheless, there is no indication regarding how to implement the new IBB services, while maintaining compatibility with older features. The present work proposes a methodology able to extending current implementations, in a systematic way, with the goal of harmonization maintenance among modules and conformance regarding current standards.

2019 IEEE International Conference on Consumer Electronics (ICCE), 2019

Interconnection among consumer electronics products is of paramount importance, mainly due to the... more Interconnection among consumer electronics products is of paramount importance, mainly due to the advent of home networks and a myriad of devices and services. In addition, when video is involved, which is common in most homes, wide bandwidth is necessary, due to content resolution. In that sense, an interesting approach is to provide connection through light links, whose spectrum is unregulated and presents abundant bandwidth. The present article addresses such a problem and proposes an infrared-light-based architecture for transmission of multimedia content in consumer electronics environments. The obtained initial results showed its effectiveness, with transmission distances exceeding 5m.

ArXiv, 2015

The software development process for embedded systems is getting faster and faster, which general... more The software development process for embedded systems is getting faster and faster, which generally incurs an increase in the associated complexity. As a consequence, consumer electronics companies usually invest a lot of resources in fast and automatic verification processes, in order to create robust systems and reduce product recall rates. Because of that, the present paper proposes a simplified version of the Qt framework, which is integrated into the Efficient SMT-Based Bounded Model Checking tool to verify actual applications that use the mentioned framework. The method proposed in this paper presents a success rate of 94.45%, for the developed test suite.

2020 IEEE International Conference on Consumer Electronics (ICCE)

Ginga is a middleware specified to offer support to execution of interactive applications, on dig... more Ginga is a middleware specified to offer support to execution of interactive applications, on digital TV (DTV) receivers. Although it offers an extensive application programming interface (API), it does not provide integration with IoT devices, which would favor its use in Internet of things (IoT) environments. This work aims to integrate Ginga with the IoT technology, through support to the message queuing telemetry transport (MQTT) communication protocol. Ginga’s API has been extended with support to MQTT, which resulted in an integrated framework regarding IoT and DTV. As a result, reference applications were developed, in order to validate the proposed framework, in a home network.

Recently, the middleware Ginga, which was developed for the Brazilian digital television system (... more Recently, the middleware Ginga, which was developed for the Brazilian digital television system (SBTVD), was updated. It is now called DTV Play and presents features related to the integrated broadcast-broadband paradigm, including execution of hypertext markup language version 5 (HTML5) applications and encrypted-content handling. However, such novelties require deeper integration with platforms, which already exists for native HTML5 engines. This work proposes a methodology for implementing those features through HTML5 engines, aiming at reducing development time and providing a simpler framework for SBTVD receivers. This approach is currently being implemented and has already proved its efficacy and efficiency.

Proceedings of the 26th ACM SIGSOFT International Symposium on Software Testing and Analysis

A MATLAB toolbox is presented, with the goal of checking occurrences of design errors typically f... more A MATLAB toolbox is presented, with the goal of checking occurrences of design errors typically found in fixed-point digital systems, considering finite word-length effects. In particular, the present toolbox works as a front-end to a recently introduced verification tool, known as Digital-System Verifier, and checks overflow, limit cycle, quantization, stability, and minimum phase errors, in digital systems represented by transfer-function and state-space equations. It provides a command-line version, with simplified access to specific functions, and a graphical-user interface, which was developed as a MATLAB application. The resulting toolbox is important for the verification community, since it shows the applicability of verification to real-world systems.

Lecture Notes in Computer Science

This paper presents optimization through counterexamples (OptCE), which is a verification tool de... more This paper presents optimization through counterexamples (OptCE), which is a verification tool developed for optimizing target functions. In particular, OptCE employs bounded model checking techniques based on boolean satisfiability and satisfiability modulo theories, which are able to obtain global minima of convex and non-convex functions. OptCE is implemented in C/C++, performs all optimization steps automatically, and iteratively analyzes counterexamples, in order to inductively achieve global optimization based on a verification oracle. Experimental results show that OptCE can effectively find optimal solutions for all evaluated benchmarks, while traditional techniques are usually trapped by local minima.

Anais de XXXVII Simpósio Brasileiro de Telecomunicações e Processamento de Sinais

Resumo-Sinais de eletrocardiograma (ECG) podem ser utilizados tanto para acompanhamento quanto di... more Resumo-Sinais de eletrocardiograma (ECG) podem ser utilizados tanto para acompanhamento quanto diagnóstico de doenças cardíacas, o que depende de infraestruturas de armazenamento e transmissão. Entretanto, como memória e banda de transmissão são recursos finitos, torna-se necessário comprimir dados de ECG. Além disso, com relação ao monitoramentoà distância, espera-se que o hardware utilizado seja simples e barato. O presente trabalho ataca o problema mencionado e propõe uma nova metodologia de compressão de sinais de ECG, onde experimentos com uma implementação desse paradigma mostraram que tal abordagemé possível e também eficaz, desde que alinhadaàs condições de cada caso específico.