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 studied. In this article, we will consider the basic terms and pillars of this science, in particular, we will talk about the types of data structures, relationships in them, and much more.
What is information and informatics?
To move on to studying the structure of the data model, you need to understand what this data and information is 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 simple way of life and traditions with the help of rock paintings.
Since then, people have made numerous scientific discoveries, collected information about their predecessors and accumulated information from everydaynews, thereby gaining more and more volumes of information and giving it such qualities as value and reliability.
Over time, the amount of information has become so vast and huge that humanity was not able to independently store it in its memory, process it manually and perform any actions on it. That is why there was a need for today's fundamental science - informatics, the scope 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 itself such basic goals as automated processing, structuring, storage and transmission of information.
In today's topic, we will specifically touch on the structuring of information, namely, we will talk about the data model. However, before that, some other points directly related to the topic of our conversation should be clarified. Namely: databases and DBMS.
Databases and DBMS
Databases (DB) are a type of structured information.
The term refers to a shared set of information that is logically related. 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, portals of fundsmedia or other corporate sources.
Database management systems (DBMS) is 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, which is 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 possible to create applications in Access itself that work on the basis of databases.
Databases can be classified according to several different criteria:
- According to the type of model (they will be discussed).
- By storage location (hard drive, RAM, optical discs).
- By type of use (local, that is, one user has access to it; medium, that is, data in the database can be viewed by several people; general - such databases are located on several servers and personal computers, that is, the ability to view information in they are en titled to a large number of people).
- According to the content of information (scientific, historical, lexicographic and others).
- By the degree of certainty of the base (centralized and distributed).
- By homogeneity (heterogeneous and homogeneous, respectively).
And also for many other, less significant features.
The main part of such a database are data models. They representa set of information structures and operations for its processing, simplifying and accelerating the process of organizing the search for the required information.
Data system models: classification
There are a wide variety of databases, but they are all based on more common and fundamental models. The classification of information data models is also divided into many different types. Here are the most commonly used categories:
- hierarchical model;
- network diagram;
- relational model;
- object-oriented schemas.
All these types of data models differ from each other 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 should be noted that the choice of 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 built in such a way that the user is presented with a data model to be used, however some of them support several different analogues at once. Let's take a look at their features one by one.
Is one of the types of data presentation models, organizing them as a collection of elements that are arranged in order from general to particular.
Structure is an inverted tree. To access one specific filethere is one way.
A hierarchical model must satisfy three basic conditions:
- Each lower level node can only be connected to one higher level node.
- There is only one main root node in the hierarchy, which is not subordinate to any other node and is at the top level.
- There is only one path to any node in the hierarchy from the root node.
Relationship type is one-to-many.
It largely relies on the hierarchical one, having quite a lot in common with it. The main difference between the two is the link type, which implies a many-to-many relationship, meaning links can exist between different nodes.
The advantage of the network model is that it consumes less PC resources in terms of memory and speed than other models.
The disadvantage of this scheme is that if you need to change the structure of the stored data, you will have to change all applications that work on the basis of this network model, since such a structure is not independent.
Is the most common today. Objects and links between them in this data model are represented by tables, and the links in them are considered as objects. The columns in such a table are called fields, and the rows are called records. Each relational model table must satisfythe following properties:
- Absolutely all its columns are homogeneous, that is, all elements 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 rows and columns appear 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 built on a tabular relational model are flexible, adaptable, and highly scalable. Each data object is broken down into the smallest and most useful fragments.
In an object-oriented data construction model, databases are defined by a set of reusable software elements with related functions. There are several different object-oriented databases:
- Multimedia database.
- Hypertext database.
The first includes media data. It can contain various images that, for example, cannot be stored in a relational model.
A hypertext database allows any database object to be linked to any other object. This is quite convenient for organizing communication in a set of disparate data, however, such a model is far from ideal when conductingnumerical analyses.
Perhaps the object-oriented model is the most popular and used model, since it can contain information in the form of tables, like relational, but, unlike it, is not limited to tabular records.
A little more information
The hierarchical model was first used in computer science in the 60s of the last century by IBM, but today its popularity has subsided due to 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 Structured Query Language (SQL). This model was released in 1970.
Thus, we can summarize the issues we have considered today with the following brief conclusions:
- Data on Personal Computers (PC) 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 the hierarchical model, the structure looks like an inverted tree.
- In the network model, there are links between different nodes.
- In the relational model, relationships between objects are represented as tables.
- 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, there may betext and images.