A particular DBMS “rules the ball” precisely at the stage of transition from an infological model of a subject domain to a datalogical model suitable for computer implementation. The DBMS is also responsible for representing the datalogical model at the physical level of computer implementation. After all, no matter how abstract the model may be, all the same, at the physical level, it usually comes down to storing data in files; these files have a certain structure, somehow distributed into directories, etc. DBMS is responsible for all this. The right requirement for the 먹튀디비 is also there.
Database classification by data model
Databases are classified according to various criteria. Note that in some cases it is more correct to speak not about the classification of databases, but about the classification of a DBMS, since it is the DBMS that determine the most significant (in particular, structural) characteristics of the databases they manage.
- The most interesting from a substantive point of view classification of the database is by the data model used, or by the structure of the data organization. According to the specified criterion, today it is customary to distinguish databases of the following types, hierarchical, network, relational and object-oriented. Immediately, we note an important fact, these types of databases arise at the stage of transition from an infological model that is invariant with respect to the structure of data organization, to a datalogical model.
The first production DBMSs used a hierarchical data model, which can be represented as a tree. The most famous DBMS using a data model of this type is the IMS (Information Management System), developed by IBM to support the Apollo lunar project. This DBMS was created to manage a huge number of parts, hierarchically interconnected nodes assembled from parts that were part of even larger modules, etc. Such constructions are easily and naturally described precisely by the hierarchical model there is no need to cite the Apollo as an example, an ordinary bicycle is enough.
The Right Model
The hierarchical model has its natural advantages and disadvantages. If we return to the idea of representing the design of a device, it is not difficult to answer the question of what parts a given unit consists of, but it is very difficult to quickly answer the question which node this part belongs to (because the connections are directed from the root down). The indicated problem (but this, of course, is not the only difficulty that arises when using the hierarchical model!) Is solved by the network model of data organization, which can be represented in the form of a directed graph of an arbitrary form (thus, in the network model, arrow connections can be arranged not only from node to the part, but also in the opposite direction).