Itinarary nets - the graphical formalism for presentation of real-time sofware application strucrures.
Itinerary network - graphical formalism for presentation structures of software applications. The formalism is focused on check logical and dynamic correctness of inter-task links in multitask software applications. The forms of itinerary nets allow to build a visual representation of inter-task links structures in software applications for real-time systems (RTS). This formalism, focused on efficient visual presentation of RTS structure, is conformed to the forms of textual formalism on the base of Extensible Markup Language (XML) that was previously suggested by authors (this XML formalism is suitable for direct automatic analysis of the developed system properties). The itinerary net markup tools are similar to the markup tools of Petri nets: they permit to represent not only static structural characteristics of multitasking software applications, but also separate system states that occur during system execution - particularly the states with rings of mutual waiting. Universal approach to checking the possibility of rings of mutual expectations (deadlocks and clinches) is formation of oriented graph - the graph of system states and transitions (such graph may be formed on the base of corresponding itinerary net). If you are using 32-bit computers with several GB of RAM this approach is suitable if the software application contains up to 20 tasks. In the case of significantly more tasks you may either use specialized approaches to evaluating logical correctness of application or use of dynamic mechanisms that ensure avoidance of the states with rings of mutual waiting (such property is provided by variants of priority ceiling protocols). Task response time estimation or feasibility analysis of the whole software application for RTS with mutual access to information resources requires take into account the values of blocking factor for high priority tasks by low priority tasks that occupy mutual resources. The methods for blocking factors estimation which are based on parametric models with ignoring of task internal structure can lead to underestimation of task response time. To find the exact evaluation of blocking factor for systems with concatenated critical intervals it is necessary to take into account the peculiarities of the structure of blocking tasks. To do this, you can use modeling of developed system by itinerary networks with building of blocking task profiles and with analysis of those cuttings of such profiles, which correspond to blocked tasks.