Marta Simeoni

Model-based performance prediction in software development: a survey

Over the last decade, a lot of research has been directed toward integrating performance analysis into the software development process. Traditional software development methods focus on software correctness, introducing performance issues later in the development process. This approach does not take into account the fact that performance problems may require considerable changes in design, for example, at the software architecture level, or even worse at the requirement analysis level. Several approaches were proposed in order to address early software performance analysis. Although some of them have been successfully applied, we are still far from seeing performance analysis integrated into ordinary software development. In this paper, we present a comprehensive review of recent research in the field of model-based performance prediction at software development time in order to assess the maturity of the field and point out promising research directions.

Petri nets for modelling metabolic pathways: a survey

In the last 15 years, several research efforts have been directed towards the representation and the analysis of metabolic pathways by using Petri nets. The goal of this paper is twofold. First, we discuss how the knowledge about metabolic pathways can be represented with Petri nets. We point out the main problems that arise in the construction of a Petri net model of a metabolic pathway and we outline some solutions proposed in the literature. Second, we present a comprehensive review of recent research on this topic, in order to assess the maturity of the field and the availability of a methodology for modelling a metabolic pathway by a corresponding Petri net.

Combining stochastic process algebras and queueing networks for software architecture analysis

We propose an integrated approach to the functional and performance analysis of Software Architectures (SAs) based on Stochastic Process Algebras (SPAs) and Queueing Networks (QNs), in order to combine their main advantages: formal techniques for the verification of functional properties of systems for SPAs, and efficient performance analysis for QNs. We first introduce Æmilia, a SPA based architectural description language for the compositional, graphical and hierarchical modeling of SAs, which is equipped with suitable checks for the detection of architectural mismatches. Then we present a systematic approach to derive QN models from Æmilia specifications. This is based on the identification of three different classes of QN basic elements --- arrival processes, buffers, and service processes --- and on syntactic restrictions to be imposed to Æmilia specifications, so that each architectural component directly falls into one of the three classes. Although performance analysis could be carried out directly on the Markov chain (MC) underlying an Æmilia specification, having a QN model allows performance indices to be evaluated possibly by exact product form solutions or by well known approximate methods. Furthermore, unlike the underlying MC, the high level of abstraction of the QN model should ease the interpretation of the performance results at the architectural description level.

Performance Evaluation at the Software Architecture Level

When tackling the construction of a software system, at the software architecture design level there are two main issues related to the system performance. First, the designer may need to choose among several alternative software architectures for the system, with the choice being driven especially by performance considerations. Second, for a specific software architecture of the system, the designer may want to understand whether its performance can be improved and, if so, it would be desirable for the designer to have some diagnostic information that guide the modification of the software architecture itself. In this paper we show how these two issues can be addressed in practice by employing a methodology relying on the combined use of AEmilia — an architectural description language based on stochastic process algebra — and queueing networks — structured performance models equipped with fast solution algorithms — which allows for a quick prediction, improvement, and comparison of the performance of different software architectures for a given system. The methodology is illustrated through a case study in which a sequential architecture, a pipeline architecture, and a concurrent architecture for a compiler system are compared on the basis of typical average performance indices.

Spatial and Temporal Refinement of Typed Graph Transformation Systems

Graph transformation systems support the formal modeling of dynamic, concurrent, and distributed systems. States are given by their graphical structure, and transitions are modeled by graph transformation rules. In this paper we investigate two kinds of refinement relations for graph transformation systems in order to support the development of a module concept for graph transformation systems. In a spatial refinement each rule is refined by an amalgamation of rules, in a temporal refinement it is refined by a sequence of rules.

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

Graph transformation systems are a formal specification technique for software systems that support the rule based specification of the dynamic behaviour of a system.Their main advantages are the intuitive visual representation of states and state transformations as graphs on the one hand, and the fully formal semantics on the other hand, that allow precise statements about the specification and tool support. In this paper we introduce refinements and modules for typed graph transformation systems to support the software specification development in both dimensions: modules for the horizontal structuring of a specification, i.e., its composition from feasible parts, and refinements for the development over time.

Refinements and modules for typed graph transformation systems

Petri Nets as a Uniform Approach to High-Level Petri Nets . . . . . 241 J. PadbergSpatial and temporal refinement relations between typed graph transformation systems have been introduced in [6,7]. In a spatial refinement a transformation rule is refined by an amalgamation of rules while in a temporal refinement it is refined by a sequence of rules: in both cases, the refinement relation supports the modeling of implementation. In the first part of this paper, we further investigate the properties of spatial and temporal refinements while, in the second part, we employ them for the development of a module concept for typed graph transformation systems. Finally, as a first step towards an algebra of modules, we introduce the operations of union and composition of modules.

Refinements of Graph Transformation Systems via Rule Expressions

Graph transformation systems are formal models of computational systems, specified by rules that describe the atomic steps of the system. A refinement of a graph transformation system is given by associating with each of its rules a composition of rules of a refining system, that has the same visible effect as the original rule. The basic composition operations on graph transformation rules are sequential and parallel composition, corresponding to temporal and spatial refinements respectively. Syntactically refinements are represented by rule expressions that describe how the refining rules shall be composed.

A graphical approach to relational reasoning

Abstract Relational reasoning is concerned with relations over an unspecified domain of discourse. Two limitations to which it is customarily subject are: only dyadic relations are taken into account; all formulas are equations, having the same expressive power as first-order sentences in three variables. The relational formalism inherits from the Peirce-Schroder tradition, through contributions of Tarski and many others. Algebraic manipulation of relational expressions (equations in particular) is much less natural than developing inferences in first-order logic; it may in fact appear to be overly machine-oriented for direct hand-based exploitation. The situation radically changes when one resorts to a convenient representation of relations based on labeled graphs. The paper provides details of this representation, which abstracts w.r.t. inessential features of expressions. Formal techniques illustrating three uses of the graph representation of relations are discussed: one technique deals with translating first-order specifications into the calculus of relations; another one, with inferring equalities within this calculus with the aid of convenient diagram-rewriting rules; a third one with checking, in the specialized framework of set theory, the definability of particular set operations. Examples of use of these techniques are produced; moreover, a promising approach to mechanization of graphical relational reasoning is outlined.

Modeling Distributed Systems by Modular Graph Transformation Based on Refinement via Rule Expressions

Due to the special requirements of distributed systems, it is important that modeling techniques for this kind of systems offer a stringent module concept. Each module has to support the encapsulation of data structure as well as functionality also at runtime. Modular graph transformation, presented in this contribution, supports these features. Modules are built up of specifications where attributed graphs describe the static data structures, whereas the dynamic behavior is modeled by the controlled application of graph rules. Rule expressions are used to formulate the control flow. Within one module, we can state a (weak) preservation of export and import behavior wrt. the local behavior in the modules body in the sense that an interface derivation is subsumed by a local derivation if it can be performed. Modules may use each other meaning that each import interface has to be connected with an export interface in a way that the import behavior is subsumed by the export behavior.