Multi-level hierarchical structuresIn the theory of systems of M. Mesarovic, special classes of hierarchical structures of the stratum type, strata, layers, differing by different principles of the interrelations of the elements within the level and various right of interference of the higher level to the organization of the relationships between the elements of the underlying are proposed.
Given the importance of these types of structures for solving the problems of enterprise management in the modern conditions of a multistructure economy, the design of complex systems, let us dwell on their characteristics in more detail.
When mapping complex systems, the main problem is to find a compromise between the simplicity of the description, which makes it possible to compile and preserve a holistic view of the object being researched or projected, and the detailed description that allows to reflect the numerous features of a specific object. One way to solve this problem is to assign a family of models to the system, each of which describes the behavior of the system from the point of view of the appropriate level of abstraction. For each level there are specific features, laws and principles that describe the behavior of the system at this level. Such a representation is called M. Mesarovici stratified, and the levels of abstraction are strata.
As the simplest example of a stratified description of M. Mesarovic, the computer is shown in the form of two strata (Figure 3.4):
• lower stratum (1) - physical operations (the system is described in the language of physical laws governing the operation and interaction of its mechanical and electronic elements);
• upper stratum (2) - mathematical and logical operations (programming and implementation of programs, implemented with abstract, non-physical concepts, information flows, programming language commands, etc.).
Fig. 3.4. Example of stratified system construction
It is noted that in principle the description of the system (computer) and other levels of abstraction, in addition to the two main ones, may be of interest. When designing some electronic components, the stratum of atomic physics can be of interest, and when developing complex software, systems with time sharing - system strata.
A similar view is used when developing banks and databases in which it is customary to allocate physical data storage level, logical and system-logical levels.
In a stratified form, you can also imagine the problem of text modeling: letters → words → sentences → paragraphs → text.
In this case, the rules for converting elements of one level to another (synthesis or, vice versa, text disassembly) can be introduced, which can be useful when creating automated information systems and systems for analytical and synthetic text processing, in the development of modeling languages, and design automation.
An example of a stratified description can also be the selection of the levels of abstraction of the system from the philosophical or theoretically cognitive description of its design to the material embodiment proposed by Yu. I. Chernyak (Figure 3.5).
Such a representation helps to understand that one and the same system at different stages of cognition and design can (and should) be described by various expressive means, i.e. as if in different "languages": philosophical, or theoretically cognitive, verbal description of the concept, concept, research - in the form of models of various kinds, helping to understand more deeply and reveal the design of the system; project - technical assignment and technical design, for the development and presentation of which you may need mathematical calculations, schematic diagrams, design - design drawings, accompanying their documentation, technological maps, standards and other technological documentation (design and technological strata can be combined), material embodiment, implementation of the system - parts, blocks, assembled product or system, principles of functioning to are reflected in the relevant regulatory and technical and regulatory documents (operating instructions, regulations, etc.).
Fig. 3.5. Strata Yu I. I. Chernyak
Such a representation can be useful in developing the methodology for designing an information system by enterprises and organizations.
Strata can be allocated according to different principles.
For example, when presenting an enterprise management system, strata can correspond to existing levels: management of technological processes (the actual production process) and organizational enterprise management. If the enterprise is included in the association, then to these two strata can be added the level of management of the association. The same principle can be used as the basis for isolating strata in the structure of the functional part of the automated control system.
A stratified representation can also be used as a means of consistently deepening the concept of the system, its detail: the lower we go down the hierarchy of strata, the more detailed is the disclosure of the system; the higher we rise, the clearer the meaning and meaning of the whole system becomes clear.
It is almost impossible to explain the purpose of the system using the lower strata elements in complex systems.
For example, studying the principles of constructing and functioning of individual cells of an organism, however detailed it may be, does not allow us to understand the construction and functioning of organs that consist of these cells, and the study of organs will not allow us to fully understand the functioning of the whole organism as a whole. But, on the other hand, in order to correctly understand and implement the overall design of the system, to construct it, it is necessary to implement the underlying strata.
The idea of detailing the system at each subsequent level was shown by Temnikov as shown in Fig. 3.6, although the term strata was not used at that time.
Fig. 3.6. Details of the system of FE Temnikov
This idea is implemented on the Internet in the form of associative links.
You can begin to study the system from any stratum, including those located in the middle of a stratified representation. In the process of research, new strata can be added, the approach to allocation of strata may change. Each strategy can use its own description, its own model, but the system is preserved until the representation on the upper stratum changes - its concept, a plan that should be sought not to distort in the disclosure on each subsequent stratum.
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