Before we learn about such a concept as data models, study their types, classifications, and also consider a detailed description, there is a need to understand the very meaning of computer science, which includes these concepts, and all areas it studies. In this article, we will consider the main terms and pillars of this science, in particular, we will talk about the types of data structures, the relationships in them and much more.
What is information and computer science?
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 the existence of human society, information played a huge role, that is, information received by a person from the vast and diverse world around us. For example, even primitive people left for us information about their simplest life and traditions with the help of cave paintings.
Since then, people have made numerous scientific discoveries, gathered information about their predecessors and accumulated information from everyday news, thereby gaining more and more information and giving it qualities such as value and reliability.
Over time, the amount of information became so vast and enormous that mankind was not able to independently store this in its memory, to engage in its manual processing and to carry out any actions on it. That is why the need arose for today's fundamental science - computer science, the study of which includes the field of human activity associated with various transformations of information. Computer science covers almost every area of our lives: from the simplest 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 specifically deal with the structuring of information, namely , we will talk about the data model. However, before this, some other points should be clarified that are directly related to the topic of our conversation. Namely: databases and DBMS.
Databases and DBMS
Type of structured information are databases (DB).
The term means a shared set of information that is logically interconnected. Databases are structures that are actively used in dynamic sites with huge amounts of information. For example, these are the resources of various online stores, media portals or other corporate sources.
A database management system (DBMS) is a set of diverse software designed to create a database, maintain them in 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 the fact that due to the presence of the VBA language, it provides for the creation of applications in Access itself, working on the basis of databases.
Databases can be classified according to several different criteria:
- By type of model (we will talk about them).
- At the place of storage (hard drive, RAM, optical disks).
- By type of use (local, that is, one user has access to it; average, that is, several people can view the data in the database; general - such databases are located on several servers and personal computers, that is, the ability to view information in them has a large number of rights people).
- According to the content of information (scientific, historical, lexicographical and others).
- According to the degree of certainty of the base (centralized and distributed).
- By homogeneity (heterogeneous and homogeneous, respectively).
And also on many other, less significant signs.
The main part of such a database is data models. They represent many information structures and operations for its processing, simplifying and speeding up the process of organizing the search for the required information.
Data System Models: Classification
There are a wide variety of databases, but all of them are created on the basis of more common and fundamental models. The classification of information data models is also subdivided into many different types. Here are the most commonly used categories:
- hierarchical model;
- network diagram;
- relational model;
- object oriented circuits.
All these types of data models differ in the nature of the presentation and storage of information in them.
Criteria for choosing the right model
The user can create a database with any of the above types. However, it is worth noting that the choice of a data model determines the dependence on some factors.
The most important criterion is whether the DBMS used by the client supports a particular model. Most DBMSs are designed so that the user is presented with a data model that should be used, but some of them support several different analogs at once. Let's look at their features individually.
Hierarchical model
It is one of the types of data presentation models, organizing them as a set of elements, which are arranged in order from general to particular.
The structure is an inverted tree. There is one way to access one specific file.
The hierarchical model must satisfy three basic conditions:
- Each node of a lower level can be associated with only one node located at a higher level.
- There is only one main root node in the hierarchy, which is not subordinate to any other node and is located at the highest 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
She relies heavily on the hierarchical, having a lot in common with her. The main difference between them is the type of connection, which implies a many-to-many relationship, that is, connections can exist between different nodes.
The advantage of the network model is that it consumes less PC resources in terms of memory and efficiency than other models.
The disadvantage of such a scheme is that if you need to change the structure of the stored data, then you will have to change all applications working on the basis of this network model, since such a structure is not independent.
Relational model
It is the most common today. Objects and relationships between them in this data model are presented in tables, and relationships in them are considered as objects. Columns in such a table are called fields, and rows are called records. Each table of the relational model must satisfy the following properties:
- Absolutely all of its columns are homogeneous, that is, all elements located in the same column must have the same type and maximum size.
- Each column has its own unique name.
- There should not be identical rows in the table.
- The order in which rows and columns follow in a 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 from a tabular relational model are flexible, adaptable, and highly scalable. Each data object is divided into the smallest and most useful fragments.
Object oriented model
In an object-oriented model for constructing data, databases are determined by a combination of reusable software elements with related functions. There are several different object-oriented databases:
- Multimedia database.
- Hypertext database.
The first includes media data. It may contain various images, which, for example, cannot be stored in the relational model.
A hypertext database allows any database object to be associated with any other object. This is convenient enough for organizing communications in a multitude of disparate data, however, such a model is far from ideal when conducting numerical analyzes.
Perhaps the object-oriented is the most popular and used model, since it can contain information in the form of tables, as well as relational, but, in contrast to it, is not limited to table recording.
A bit of additional information
For the first time in computer science, the hierarchical model was used in the 60s of the last century by IBM, but today its popularity has fallen due to low efficiency.
The network data model was popular already in the 70s, after it was officially determined by the Conference on Database System Languages.
Relational databases are usually written in Structured Query Language (SQL). Such a model was published in 1970.
conclusions
Thus, we can summarize the issues we have discussed today with the help of the following brief conclusions:
- Data on Personal Computers (PCs) can be stored structurally in the form of 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 is an inverted tree.
- In the network model, communications are between different nodes.
- In the relational model, relationships between objects are presented in tabular form.
- In an object-oriented model, relationships between elements can be represented by tables, but are not limited to them.
In the latter case, for example, the presence of text and images is possible.