Trace Construction Methodology and  Applications (more)

Broadly speaking, we want to look at the observation of dynamic processes from the traces they leave.

We focuse particularly on providing semantics to tracers, i.e. to generators of traces, and the traces they produce. We seek semantics as independent as possible from those of the processes or from the ways the tracers produce them.

We must also clearly distinguish what depends on what we call here ``trace''and what depends on process analysis (monitoring, presentation of the traces or pretty printing, visualization, performance analysis, debugging, ...), which all, in one way or another, directly or indirectly, from inside or independently, in synchronous or asynchronous mode, use traces for analytical purposes but do not produce them. This study does not concern the nature nor the form of these process observers. They are always, by definition, external, i.e. outside of the observed process  and use the traces as input data.

One can always consider that between an observer (or process observer) and an observed phenomenon (or observed process)  there is an object that we call  actual trace. The actual trace is the actually recognizable footprints left by a process or a set of processes, and therefore ``readable'' by other processes, in real time or post mortem. The observed phenomenon  is regarded here as one closed process (this concerns all the data and functions that it handles), which we only known by its actual trace.

We will also introduce the concept of  virtual trace. The virtual trace is the sequence of events representing the evolution of a state which contains all that one can or wants to know about this or these processes, i.e. all their ``observables''. This development may eventually be formalised by a model of states transitions, i.e. by a state domain and a transition function formalizing the step from one state to another. This semantics, equipped with all extraction operations producing the actual trace, will be called the  observational semantic (OS) because it represents all what one is likely to know or to describe about the process, viewed from outside of it. However, the virtual trace itself, taken alone, can also be regarded as a semantics.

Finally, this approach is based on the concept of full trace (actual or virtual)} (full in the sense that the totality of knowledge regarding the observed process is there explicitly or implicitly contained). This constitutes a basis for studying the modular construction of tracers and traces, using only the notions of trace enrichment, sub-trace, fusion, trace abstraction. We also study the notion of genericity of a trace, i.e. the possibility to give semantics to a tracer, which is valid for a family of observed processes.

We are currently investigating the use of the fluent calculus as modeling tool for the observational semantics in the framework of the projets C4RBCP.

Illustration of the trace semantics