Formal specification and simulation of software through graph grammars: a general but minimal approach

This report gives an overview of the current status and plans to construct a prototype environment of advanced tools for software and hardware development based on the use of wide-spectrum languages. The wide-spectrum languages include Anna (ANNotated Ada), and TSL (Task Sequencing Language). The tools described here provide interactive aid at all stages in the system development process. Special emphasis is placed on distributed computing, both in providing tools for handling parallelism in the subject system, and in designing tools that utilize parallelism in the programming environment. Applications of these tools include requirements analysis, formal specification, rapid prototyping, testing, formal verfication and construction of self-testing Ada software for multi-processor systems.The report describes an existing environment of prototype tools supporting applications of Anna and TSL to formal specification and testing of Ada software. The new environment tools will be based on component tools already developed at Stanford and proven to be portable to various Ada environments. All tools are implemented in Ada and are intended to interface with standard components of Ada programming environments.

An alternative scheme to formal software specification is explicitly proposed. In our approach, a formal software specification is formally defined as a set of decision rules performed by a software system. We propose a set of graphical notations called Requirements Particle Network (RPN), to describe the essential preconditions and operations needed by a software system according to the decision rules. A RPN consists of a set of particles and edges to construct a visual model of a decision rule during the software analysis phase. In addition, a number of transformation rules are proposed to perform the formal specification synthesis. A set of predefined formal requirements particle definitions is written in prior and reused during the transformation steps. A developer is provided a practical mean to write a formal specification with a brief experience in mathematical background. In this research, we demonstrate the Z formal specification synthesis using RPN. The usability of the RPN approach is investigated by conducting a workshop. The result indicates that a developer with experience in writing data flow diagram is capable to produce a complete and consistent RPN. Moreover, we show a case study of applying RPN to construct a composite operation to be used in database applications

The domain of transformation systems has been introduced to provide a general integration framework for formal specifications. In this chapter an application of the integration approach to less formal software specifications is discussed. For that purpose models given in the Unified Modeling Language (UML) are considered: class diagrams for the specification of the structure and architecture of the system, and statechart and sequence diagrams for the specification of its behaviour. Analogous to the applications to specification formalisms presented in the previous chapters, the basic idea here is to interpret specifications semantically by sets of transformation systems, exhibit their correspondences, and thereby to check whether a common interpretation of all considered specifications is possible. As opposed to the former examples, however, the investigation cannot be completely formal, since the semantics of the given UML languages is not formally defined. That means the correctness of the transformation system semantics cannot be formally proved. To cope with this situation the interpretation will be open w.r.t. certain semantic decisions, which is then treated as parameters of possible admissible interpretations. On the other hand, the interpretation in the transformation system reference model provides the means for the formalisation and thus precision of the considered software specification languages.KeywordsState MachineUnify Modeling LanguageClass DiagramSequence DiagramClass GraphThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Storm tide (combination of storm surge and the astronomical tide) flooding is a natural hazard with significant global social and economic consequences. For this reason, government agencies and stakeholders need storm tide flood maps to determine population and infrastructure at risk to present and future levels of inundation. Computer models of varying complexity are able to produce regional-scale storm tide flood maps and current model types are either static or dynamic in their implementation. Static models of storm tide utilize storm tide heights to inundate locations hydrologically connected to the coast, whilst dynamic models simulate physical processes that cause flooding. Static models have been used in regional-scale storm tide flood impact assessments, but model limitations and coarse spatial resolutions contribute to uncertain impact estimates. Dynamic models are better at estimating flooding and impact but are computationally expensive. In this study we have developed a dynamic reduced-complexity model of storm tide flooding that is computationally efficient and is applied at hyper-resolutions (<100 m cell size) over regional scales. We test the performance of this dynamic reduced-complexity model and a separate static model at three test sites where storm tide observational data are available. Additionally, we perform a flood impact assessment at each site using the dynamic reduced-complexity and static model outputs. Our results show that static models can overestimate observed flood areas up to 204 % and estimate more than twice the number of people, infrastructure, and agricultural land affected by flooding. Overall we find that that a reduced-complexity dynamic model of storm tide provides more conservative estimates of coastal flooding and impact.

The more popular it is to build an application from reusable software components, the more desperate is the need for showing correctness of such a composition. This requires on one hand, being able to formally specify behavior of software components, while, on the other hand, providing appropriate tool support for verification of correctness of the composition. In this paper, we suggest use of the formalism of Extended Behavior Protocols and present a tool chain for verification of composition correctness of component applications. The advantage of the proposed approach is using a well-tested and supported model checker Spin as a backend. As a proof of the concept, we share our experience with application of the method.

A recent method combines model checkers with specifica- tion-based mutation analysis to generate test cases from formal software specifications. However high-level software specifications usually must be reduced to make analysis with a model checker feasible.

Formal Software Specification with Refinements and Modules of Typed Graph Transformation Systems

Using graph transformation as a formalism to specify access control has several advantages, from the intuition provided by the visual aspect to the precise semantics and the systematic verification of constraints. Graph Transformations provide a uniform and precise framework for the specification of access control policies. After reviewing the basic notations of graph transformation, this article presents specification formalisms for workflow delegation policies using graph transformation. The authorization states are represented by graphs and state transition by graph transformation. The proposed formalization provides an intuitive description for the manipulation of graph structures as they occur in workflow delegation and a precise specification of consistency conditions on graphs and graph transformations. We specifies a type graph to represents the type information in the graph transformation for workflow delegation, a set of rules to build the system states and sets of positive and negative constraints to specify wanted and unwanted framework.

In this paper, we discuss the relation between liquidity and the business cycle.There are some reasons that we should link liquidity with the business cycle. The“flight to liquidity” or “flight to quality” hypothesis might be the most important one. It is more likely that an investor shifts his portfolio from those stocks with lower liquidity or higher risk when the economy is in a recession.Instead of business cycle measures, we use the NBER recession signal as the proxy of real economy. We apply dynamic and static probit model to monthly liquidity proxy, because the NBER recession is not always available in current period. Besides we use Amihud (2002) ILR as our liquidity proxy.The dynamic probit model with liquidity added does not result in a significance improvement on prediction. No matter in sample or out of sample, the pure dynamic probit model performs well with itself history only. However, as we mentioned earlier, NBER recession signal is usually announced well until the recession has happened for months, leading to an infeasibility to implement dynamic model. On the other hand, liquidity plays an important role in static probit model. We find a robust positive relation between liquidity and recession. Adding liquidity as a predictor in the static model would significantly improve the forecast accuracy in th short horizon. This observation remains robust with comparison to other financial variables ( e.g. term spread, credit spread, market volatility, and excess return). We also find the existence of “size effect” that small firm is more sensitive to future recession. Our finding above is consistent with our claims of “flight to liquidity; that is, it is more likely for market participants to shift his portfolio from those stock with lower liquidity or higher risk in advance when the economy would be in a recession. The primary contribution of this paper is that liquidity proxy, Amihud’s liquidity proxy here, does provide useful information when predicting the future recession. We find that the liquidity proxy performs well especially in a short prediction horizon. Besides, the liquidity of small firms is more informative in prediction.

Graph grammars can easily be considered as models for rule-based systems where solving state-space problems essentially requires searching. Since many AI problems are naturally graphical, graph grammars could narrow the usual gap between a problem and its formal specification.

UML state machines are quite popular and useful to specify dynamic components of software systems. They have a formal static semantics but their execution semantics is described only informally. Graph transformation, on the other hand, constitutes a well-studied area with many theoretical results and practical application domains. In this paper, an operational semantics for a subset of UML state machines is proposed which is based on graph transformation. In more detail, a UML state machine is described as a structured graph transformation system in such a way that the wellformedness rules of UML state machines are satisfied and the firing of a (maximum) set of enabled non-conflicting transitions corresponds to the application of a graph transformation rule. The presented approach uses the concept of transformation units, a recently developed modularization concept for graph transformation systems.

PurposeThe purpose of this paper is to present the ability of Z‐notation to formulate formal requirements specification of huge application software based on an example of the Manufacturing Resource Planning (MRP II) Standard System. Z‐notation is using formal transformation approach to obtain operating software instead of traditional programming. The original MRP II software requirement specification possesses descriptive form extended by list of control questions. To make formal requirements specification, the original specification must be extending by some definition taken after APICS Dictionary. The definitions respect such concept as: item, item code, location, and order.Design/methodology/approachWriting schemas based on subsystem order of MRP II Standard System and treating the system as three level structures (user interface, business logic, and database), the schemas described business logic level only. As a conclusion was necessity to extend descriptive requirements specification by definitions. The limited size of the presentation contains few examples of formalization process only mainly limited to the main schemas as: item system (full definition), inventory system, bill of material, work centers and routings, generic order system, master production schedule, and material requirement planning.FindingsAs a result of the research, it can be said that Z‐notation apparatus is sufficient to build requirements specifications of big application systems like MRP II, enterprise resource planning, or customer relationship management.Originality/valueLibraries of typical algorithms like MRP II designed through formal approach could replace traditional programming and open new prospects in the future development of broad computerization.

On Formal Specification of Software Components and Systems

In digitally controlled DC-DC converters with a single voltage feedback loop, the two quantizers, namely the A/D converter and the digital pulse-width modulator (DPWM), can cause undesirable limit-cycle oscillations. In this paper, static and dynamic models that include the quantization effects are derived and used to explain the origins of limit-cycle oscillations. In the static model, existence of DC solution, which is a necessary no-limit-cycle condition, is examined using a graphical method. A concept of amplitude and offset dependent gain is introduced to extend the describing function method and derive the dynamic system model. From the static and dynamic models, no-limit-cycle conditions associated with A/D, DPWM and compensator design criteria are derived. The conclusions are illustrated by simulation and experimental examples.

In digitally controlled dc-dc converters with a single voltage feedback loop, the two quantizers, namely the analog-to-digital (A/D) converter and the digital pulse-width modulator (DPWM), can cause undesirable limit-cycle oscillations. In this paper, static and dynamic models that include the quantization effects are derived and used to explain the origins of limit-cycle oscillations. In the static model, existence of dc solution, which is a necessary no-limit-cycle condition, is examined using a graphical method. Based on the generalized describing function method, the amplitude and offset-dependent gain model of a quantizer is applied to derive the dynamic system model. From the static and dynamic models, no-limit-cycle conditions associated with A/D, DPWM and compensator design criteria are derived. The conclusions are illustrated by simulation and experimental examples