1976770
Self-independent Petri Nets for Distributed Systems
We propose that asynchronous mechanism for communication should be considered as a primitive for semantic models of distributed systems in contrast to the synchronous mechanism (hand-shaking) of CSP (Hoare, 1985) and of CCS (Milner, 1989). By doing so, we present an approach to producing a deadlock-free system, and give a denotational model for CCS in a non-interleaving fashion.
1315911
An Object Semantic Model of SOFL
SOFL (Structured-Object-based-Formal Language) is recently proposed to combine the advantages of formal methods, structured methods and object-oriented methodology into one method for software development. SOFL integrates modeling techniques from VDM (for specifying system component state) and data flow diagrams with Petri nets (for specifying system behaviours and interaction). To support the standardisation and the tool support for SOFL, a formal semantics of the language is desirable. As SOFL is under further development, the semantic representation of current SOFL needs to be easily reused and extended. In this paper, an object-oriented approach is taken to specify the semantics of SOFL and this approach is proved to be effective in providing a modular and reusable semantic representation. Object modeling techniques, such as inheritance is used to illustrate the common and the differences between various SOFL graphical constructs; object containment is used to capture the acyclic structure of SOFL hierarchical module decomposition.
18693305
Verifying Consistency and Validity of Formal Specifications by Testing
Detecting faults in specifications can help reduce the cost and risk of software development because incorrect implementation can be prevented early. This goal can be achieved by verifying the consistency and validity of specifications. In this paper we put forward specification testing as a practical technique for verification and validation of formal specifications. Our approach is to derive proof obligations from a specification and then test them, in order to detect faults leading to the violation of consistency or validity of the specification. We describe proof obligations for various consistency properties of a specification, and suggest the use of five strategies for testing them. We provide a method for testing implicit specifications by evaluation rather than by prototyping, and criteria for interpreting the meaning of test results.
9811887
A formal operational semantics for SOFL
SOFL (Structured-Object-Based-Formal Language) is a formal language and method for practical systems development. As a language, it integrates data flow diagrams, VDM-SL, and Petri nets to provide a graphical and textual formal notation for specification construction. Previous publications introducing SOFL are based on its informal semantics. We provide a formal operational semantics which gives a firm foundation for consistent understanding and application of SOFL in practical systems development. Development of the semantics, and application of SOFL to practical systems, have led to some changes in the original definitions. This formal semantics will serve as a firm foundation for building an effective support environment for SOFL.
6009818
A Formal Definition of FRSM and Applications
FRSM (Formal Requirements Specification Method) is a structured formal language and method for requirements analysis and specification construction based on data flow analysis. It uses a formalized DeMarco data flow diagram to describe the overall structure of systems and a VDM-SL like formal notation to describe precisely the functionality of components in the diagrams. This paper first describes the formal syntax and semantics of FRSM and then presents an example of using the axiom and inference rules given in the definition of the formal semantics for checking consistency of specifications. A case study of applying FRSM to a practical example is described to demonstrate the principle of constructing requirements specifications and to uncover the benefits and deficiencies of FRSM.
30881235
Criteria for generating specification-based tests
This paper presents general criteria for generating test inputs from state-based specifications. Software testing can only be formalized and quantified when a solid basis for test generation can be defined. Formal specifications of complex systems represent a significant opportunity for testing because they precisely describe what functions the software is supposed to provide in a form that can easily be manipulated. These techniques provide coverage criteria that are based on the specifications, and are made up of several parts, including test prefixes that contain inputs necessary to put the software into the appropriate state for the test values. The test generation process includes several steps for transforming specifications to tests. Empirical results from a comparative case study application of these criteria are presented.
3186847
A Hardware/Software Framework for Real-Time Spiking Systems
One focus of recent research in the field of biologically plausible neural networks is the investigation of higher-level functions such as learning, development and modulatory functions in spiking neural networks. It is desirable to explore these functions in physical neural network systems operating in real-time. We present a framework which supports such research by combining hardware spiking neurons implemented in analog VLSI (aVLSI) together with software agents. These agents are embedded in the spiking communication of the network and can change the parameters and connectivity of the network. This new approach incorporating feedback from active software agents to aVLSI hardware allows the exploration of a large variety of dynamic real-time spiking network models by adding the flexibility of software to the real-time performance of hardware.
18592302
A Winner-Take-All Circuit with Controllable Soft Max Property
I describe a silicon network consisting of a group of excitatory neurons and a global inhibitory neuron. The output of the inhibitory neuron is normalized with respect to the input strengths. This output models the normalization property of the wide-field direction-selective cells in the fly visual system. This normalizing property is also useful in any system where we wish the output signal to code only the strength of the inputs, and not be dependent on the number of inputs. The circuitry in each neuron is equivalent to that in Lazzaro's winner-take-all (WTA) circuit with one additional transistor and a voltage reference. Just as in Lazzaro's circuit, the outputs of the excitatory neurons code the neuron with the largest input. The difference here is that multiple winners can be chosen. By varying the voltage reference of the neuron, the network can transition between a soft-max behavior and a hard WTA behavior. I show results from a fabricated chip of 20 neurons in a 1.2 µm CMOS technology.
1310843
AER EAR: A Matched Silicon Cochlea Pair With Address Event Representation Interface
In this paper, we present an analog integrated circuit containing a matched pair of silicon cochleae and an address event interface. Each section of the cochlea, modeled by a second-order low-pass filter, is followed by a simplified inner hair cell circuit and a spiking neuron circuit. When the neuron spikes, an address event is generated on the asynchronous data bus. We present the results of the chip characterization and the results of an interaural time difference based sound localization experiment using the address event representation (AER) EAR. The chip was fabricated in a 3-metal 2-poly 0.5-mum CMOS process
9506912
Quantifying Input and Output Spike Statistics of a Winner-Take-All Network in a Vision System
Event-driven spike-based processing systems offer new possibilities for real-time vision. Signals are encoded asynchronously in time thus preserving the time information of the occurrence of an event. The paper examines this form of coding using experimental data from a multi-layered multi-chip system which consists of an artificial retina, a convolution filter bank and a winner-take-all network which detect the position of a moving object. The spike outputs of the convolution stage can be described by an inhomogeneous Poisson distribution of Gaussian profile, although the underlying building blocks are completely deterministic and exhibit only a small amount of variation. The authors discuss a method for measuring the accuracy of the asynchronous spiking representation in both time and value, thereby quantifying the performance of the winner-take-all network in determining the position of a ball rotating in front of the system.
7160160
QoS-UniFrame: a Petri net-based modeling approach to assure QoS requirements of distributed real-time and embedded systems
Assuring quality of service (QoS) requirements is critical when assembling a distributed real-time and embedded (DRE) system from a repository of existing components. This paper presents a two-level approach for assuring satisfaction of QoS requirements in the context of a reduced design space for DRE systems. A dynamic and parallel approach is introduced to prune off the infeasible design spaces at the first level. Evolutionary algorithms cooperating with a domain-specific scripting language then discard less probable design spaces using statistics. These techniques fulfill the collective objectives of pruning and assuring the design space at system assembly time.