functional event of the computational process
structural complexity of software system
three-level scheme interaction of software modules
large-scale applied software complexes
R.V. Buhvalov, S.V. Petrovsky
Creation of applied software complexes (ASC) for big automatically functioning information and control systems (AFICS) at all stages of their development represented serious scientific – technical problem, and, recently (since second half of 90-th years) on the first place there were technological aspects of this problem. Search of ways and methods of reduction of the general labor input of works at all stages of its creation, first of all – at stages of ASC initial working out and debugging, became the overriding problem of developers of large-scale applied software complexes for AFICS.
As the retrospective analysis of some consistently created realizations of large-scale ASC for one concrete AFICS shows, an essential contribution in increasing of the general technological level of ASC working out at the previous realization was a formation in ASC structure a set of specialized services intended for centralized performance of various special-purpose operations by inquiries of applied program modules of ASC (in addition to "regular" services of an operating system).
Use of the specialized services which had simple enough interfaces with applied program modules (APM), has brought the considerable reduction of the general labor input of works (especially in respect of the organization of APM interaction among themselves under the information and on operating influences), has essentially simplified and has accelerated works on ASC assemblage and complex debugging.
Such specialized services at the previous ASC realization concern, for example:
service of maintenance of APM interaction with "exchange" data files;
service of maintenance of APM operating interaction among themselves;
service of maintenance of automatic message formation on key events of information treatment process in ASC on means of display of command station;
service of maintenance of ASC interaction with chief operator of ASC and also variety of other.
The organization of ASC interaction with specialized (additional) services has been realized in the form of the traditional two-level "client-server" scheme, where ASC APMs acted as clients of specialized services. We will notice that in real ASC typical APM cooperates, as a rule, with 3 – 5 services, each of which has own (unique) client interface.
At creation of ASC for the AFICS on last of considered realizations (2004 – 2009 years) the additional specialized services applied at the previous realization, also have been formatted in ASC structure. However for the further reduction of the general labor input of creation of ASC it was required to find ways of decrease in structural ("constructive") ASC complexity at the expense of reduction of quantity and a variety of interactions between ASC APMs, and also at the expense of simplification and unification of such interactions.
Thereupon authors it was offered to introduce a new intermediate level into the scheme of ASC interaction organization – so-called Service of Functional Events of computing process (SFE). Thus each APM of ASC should cooperate as the client only with this intermediate service through its universal interface. In turn, SFE should realize all kinds of diverse interactions with all other additional services used in ASC, as their client.
For functioning of such universal "intermediary" it is necessary all basic "structural" information on existence of certain communications between APM in ASC, and also all information on attributes of these communications to concentrate in special base of the "structural" data which will be used by SFE.
The three-level model of ASC APMs interaction organization on the basis of intermediate service of functional events considered in article, used at creation of last realization of ASC for the AFICS, represents an effective method of decrease in labor input of works on ASC structure formation, acceleration of complex debugging and working off of all kinds of interaction of ASC APMs.
Besides, application of service of functional events reduces computing complexity and raises reliability of cooperating APM of ASC at the expense of centralization of the information on functional events and operations on their working off.