Before we learn about such a thing asdata models, we will study their types, classifications, and also we will consider the detailed description, there is a need to realize the very meaning of informatics, which includes these concepts, and all the areas studied by it. In this article we will discuss the basic terms and pillars of this science, in particular, we will talk about the types of data structure, the connections in them and much more.
What is information and informatics?
To proceed to the study of the structure of the data model, you need to understand what this data and information are in principle.
Absolutely at any moment of existencehuman society played a huge role information, that is, information obtained by a person from the vast and diverse world around us. For example, even primitive people left for us information about their simple life and traditions with the help of cave paintings.
Since then, people have committed multiple scientificdiscoveries, collected information about their predecessors and accumulated information from everyday news, thereby gathering more and more information and giving it qualities such as value and reliability.
Over time, the amount of information has become soextensive and huge that humanity was not able to independently store it in its memory, engage in its manual processing and perform any actions on it. That is why the need has arisen for today's fundamental science - computer science, the scope of study of which includes the field of human activity associated with various transformations of information. Informatics covers almost every area of our life: from simple mathematical calculations to complex engineering and architectural design, as well as the creation of animated and animated films. It sets such basic goals as automated processing, structuring, storage and transmission of information.
In today's topic, we will touch specificallystructuring information, namely, let's talk about the data model. However, before this we should clarify some other points directly related to the topic of our conversation. Namely: the database and DBMS.
Databases and DBMS
Type of structured information are databases (DB).
Термин означает совместно используемый набор information that is logically related. Databases are structures that are actively used in dynamic sites with huge amounts of information. For example, these are resources from various online stores, media portals or other corporate sources.
Системами управления базами данных (СУБД) called a set of various software designed to create databases, maintain them in the proper form and organize a quick search for the required information in them. An example of a widely used DBMS is Microsoft Access, released in a single line of Microsoft Office. A distinctive feature of this DBMS is that due to the presence of the VBA language in it, it is planned to create applications in Access itself that work on the basis of databases.
Databases can be classified according to several different criteria:
- By type of model (they will be discussed).
- By storage location (hard disk, RAM, optical disks).
- By type of use (local, i.e. access toit has one user; medium, that is, data in the database can be viewed by several people; common - such databases are located on several servers and personal computers, that is, the ability to view information in them is entitled to a large number of people).
- On the content of information (scientific, historical, lexicographical and others).
- According to the degree of certainty of the base (centralized and distributed).
- For homogeneity (heterogeneous and homogeneous, respectively).
And also in many other, less significant features.
The main part of this database are data models.They are sets of information structures and processing operations that simplify and accelerate the process of organizing the search for the required information.
Data system models: classification
There are a variety of databases, but allthey are created on the basis of more common and fundamental models. The classification of information data models is also divided into many different types. We give the most frequently used categories:
- hierarchical model;
- network diagram;
- relational model;
- object oriented schemes.
All these types of data models differ in the nature of the presentation and storage of information in them.
Criteria for selecting the desired model
The user can create a database with any of the above described types. However, it is worth noting that the choice of data model determines the dependence on some factors.
The main criterion is thatWhether the client uses the DBMS to support a specific model. Most DBMSs are designed so that the user is presented with a data model that should be used, however some of them support several different analogues at once. Let's look at their features separately.
Hierarchical model
It is one of the types of data representation models, organizing them as a set of elements that are arranged in order from general to specific.
The structure is an inverted tree. To access one specific file there is one path.
The hierarchical model must satisfy three basic conditions:
- Each node at a lower level can only be associated with one node at a higher level.
- In the hierarchy there is only one main root node, which does not obey any other node and is located at the topmost level.
- To any node in the hierarchy, there is only one path from the root node.
The type of connection is one-to-many.
Network model
It largely relies on the hierarchical, havingshe has a lot in common. The main difference between them is the type of connection, which implies a many-to-many relationship, that is, links can exist between different nodes.
The advantage of the network model is that it spends less PC resources in terms of memory and efficiency than other models.
The disadvantage of this scheme is thatif you need to change the structure of the stored data, then you will have to change all the applications running on the basis of this network model, since such a structure is not independent.
Relational model
Is the most common to dateday. Objects and relationships between them with such a data model are represented by tables, and links in them are considered as objects. Columns in such a table are called fields, and rows are records. Each table of the relational model must satisfy the following properties:
- Absolutely all its columns are homogeneous, that is, all elements that are located in one column must have the same type and maximum allowable size.
- Each column has its own unique name.
- There should not be identical rows in the table.
- The order in which the rows and columns follow in the table can be arbitrary.
The relational model also takes into account the types of relationships between these tables, including one-to-one, one-to-many, and many-to-many relationships.
Databases created on the basis of a tabular relational model are flexible, adaptable and well scalable. Each data object is divided into the smallest and most useful fragments.
Object oriented model
In the object-oriented construction modeldatabase data is determined by a set of reusable software elements with related functions. There are several different object-oriented databases:
- Multimedia database.
- Hypertext database.
The first includes data media. It may contain various images, which, for example, cannot be stored in the relational model.
Hypertext database allows anyoneobject base to be associated with any other object. This is quite convenient for organizing communication in a variety of disparate data, however, this model is far from ideal when conducting numerical analyzes.
Perhaps object-oriented is the mostpopular and used by the model, since it may contain information in the form of tables, like the relational one, but, unlike it, is not limited to tabular writing.
Some additional information
For the first time in computer science, the hierarchical model was used in the 1960s by IBM, but today its popularity has diminished due to its low efficiency.
The network data model was already popular in the 70s, after it was officially defined by the Conference on Database System Languages.
Relational databases are usually written in a structured query language (SQL). Such a model was published in 1970.
conclusions
Thus, we can summarize the issues we have discussed today with the following brief conclusions:
- Data on Personal Computers (PCs) can be stored structurally as special databases.
- The core of any database is its model.
- There are four main types of data models: hierarchical, network, relational, object-oriented.
- In a hierarchical model, the structure externally is an inverted tree.
- In the network communication model there are between different nodes.
- In the relational model, relationships between objects are presented in the form of tables.
- In the object-oriented model, relationships between elements can be represented by tables, but are not limited to them.
In the latter case, for example, text and images are possible.
