What is the conceptual structure of a database Describe its characteristics and design strategies

Database design.

6 basic steps: requirements analysis; Conceptual structural design.

logical structure design; physical structure design; database implementation; Database operation and maintenance.

Features: (1) It can truly and fully reflect the real world, including the connection between things and things, meet the user's requirements for data processing, and is a real model of the real world; Hall 2.

2) easy to understand, so that it can be used to exchange ideas with users who are not familiar with computers, and the active participation of users is the key to the success of database design 2;

3) Easy to change, when the application environment and application requirements change, it is easy to modify and expand the conceptual model;

4) It is easy to convert to various data models such as relational, mesh, and hierarchical. There are generally four design strategies for conceptual structures. Design strategy: (1) top-down, that is, first define the framework of the global conceptual structure, and then gradually refine it;

2) bottom-up, i.e., first define the conceptual structure of each local application, and then integrate them to obtain the global conceptual successor; and (3) expand gradually, first defining the most important core conceptual structure, and then expanding outwards to snowball.

to gradually generate other conceptual structures, up to the overall conceptual structure;

4) Hybrid strategy, that is, the combination of top-down and bottom-up, using the top-down strategy to design a global concept lattice framework, and using it as the skeleton to integrate the local conceptual structures designed by the bottom-up strategy.

Database systems.

Also known as DBS, it is a system composed of a database and its management software. Commonly used systems include Oracle, DB2, and SQL Server Access.

Its characteristics can be summarized as follows: to provide users with an easy-to-use user interface, and to safely manage and maintain data and its relationships.

Through powerful mechanisms such as indexing, query optimization, transaction processing, concurrent access control, triggers, and error recovery, the database management system effectively ensures the efficiency of massive data access, ensures the integrity and consistency of data, and provides data reliability and security, so as to have incomparable advantages over other data management methods.

Significant advantages:

1. It is easy to build and maintain the tree structure of data;

2. It is convenient to maintain the semantics of the order of the data;

3. It is easy to combine with the tree control of the development platform.

A: Features of the XML data model.

XML is a standard developed by the W3C and is designed to be a hybrid language to exchange information between users and programs.

It has a series of excellent features, such as scalability, simplicity, self-description, separation of structure, content, and presentation.

As a result, XML is strongly supported in both the free and commercial software communities, providing developers with a great deal of flexibility.

b: Advantages of the XML data model.

The XML data model itself is a tree-like model, and a well-formed and validated XML document is parsed by the DOM to create a tree in memory.

As a result, the XML data model is well and easily maintained by the XML document parser for the semantics and hierarchy of real-world data, with minimal effort on the part of developers.

In addition, the dynamic maintenance of this semantic semantics and hierarchy is relatively simple.

In addition, XML parsers are components with standard interfaces, which allows developers to avoid duplicate development and distribution of interface programs, as well as reduce the corresponding interface program testing and maintenance overhead.

1. Data

1. Data is the result of facts or observations, a logical induction of objective things, and an unprocessed raw material used to represent objective things.

2. The data can be continuous values, such as sound and image, which are called analog data; It can also be discrete, such as symbols, words, and is called numerical data.

3. In a computer system, data is represented in the form of a binary information unit.

2. Databases

A database is a repository of data. It has a large storage space and can store millions, tens of millions, and hundreds of millions of pieces of data. However, the database does not store data at random, and there are certain rules, otherwise the query efficiency will be very low.

Today's world is an internet world full of data, and it is full of data. That is, this Internet world is the world of data. There are many types of data, such as travel records, consumption records, missed web pages, messages sent, and so on.

In addition to text-type data, images, **, and sounds are all data.

3. Database management system

1. Database management system (database management system) is a large-scale software for manipulating and managing databases, which is used to establish, use and maintain databases, referred to as DBMS. It manages and controls the database in a unified manner to ensure the security and integrity of the database. Users access the data in the database through the DBMS, and the database administrator also uses the DBMS to maintain the database.

2. It can support multiple applications and users to establish, modify and query databases at the same time or at different times in different ways. Most DBMS provide Data Definition Language (DDL) and Data Manipulation Language (DML) for users to define the schema structure and permission constraints of the database, and to append and delete data.

Fourth, the database system

A database system (DBS) consists of software, databases, and data administrators. Its software mainly includes operating systems, various host languages, utilities, and database management systems. The database is managed by the database management system, and the insertion, modification and retrieval of data are all carried out through the database management system.

Data stewards are responsible for creating, monitoring, and maintaining the entire database so that the data can be effectively used by anyone who has access to it. Database administrators are generally people with a high level of business and deep qualifications.

5. The relationship between data, databases, database management systems, and database systems

1. First of all, the database system (baidbs) includes a database (DB) and a database management system (DBMS), the database management system includes a database, and the database includes data.

2. The database is a warehouse used to store data.

3. The database management system is a system for manipulating and managing databases.

In the conceptual design phase of database design, common methods and tools to represent the conceptual structure are entity contact method and entity contact diagram.

Database design refers to the construction of the optimal database schema for a given application environment, and the establishment of the database and its application system so that it can effectively store data and meet the application needs (information requirements and processing requirements) of various users. In the field of databases, the various types of systems that use databases are often referred to collectively as database application systems.

The design content of database design includes: requirements and brother analysis, conceptual structure design, logical structure design, physical structure design, database implementation, and database operation and maintenance.

Database design refers to the process of designing the structure of the database and establishing the database on a specific database management system according to the needs of users. The database system needs the support of the operating system.

Database design is the technology for establishing the database and its application system, and it is the core technology in the development and construction of the information system. Due to the complexity of the database application system, the database design becomes extremely complex in order to support the operation of related programs, so the optimal design cannot be achieved overnight, but can only be a process of "repeated exploration and gradual refinement", that is, the process of planning and structuring the data objects in the database and the relationships between these data objects.

The conceptual structure of the database should be designed during the system analysis phase.

System analysis is the most basic method of consulting research, we can regard a complex consulting project as system engineering, through system objective analysis, system element analysis, system environment analysis, system resource analysis and system management analysis, we can accurately diagnose the problem, profoundly reveal the cause of the problem, and effectively improve the solution and meet the needs of customers.

The main task of the system analysis is to analyze the overall management status and information processing process of the organization by bringing together the documents obtained from the detailed investigation of the system. It focuses on analysis from the perspective of the whole business process.

The main contents of the analysis are: whether the business and data flow is smooth and reasonable; the relationship between data, business processes, and implementation management functions; Whether the reform of the old system management model and the implementation of the new system management method are feasible and so on.

The purpose of the system analysis is to identify the needs of users and their solutions, and the results of these needs include: the developer's understanding of the current state of organizational management; user demand for information system functionality; data and business processes; management functions and management data indicator system; The new system is proposed to be changed and the new management model is added, etc.

Systems Analysis Method** in Systems Science. Systems science is a new scientific department that has developed rapidly since the 40s of the 20th century and spans various disciplines, which investigates and studies the entire objective world from a systematic perspective or perspective, and provides scientific theories and methods for human beings to understand and transform the world.

Answer] :d In database design, the results of demand analysis form a data flow diagram; In the conceptual design stage, the E-R (Entity Connection) method is used to describe the conceptual model and form the E-R diagram. For relational databases, the task in the design phase of logical leasing is to convert the e-r diagram (conceptual model) into a guanhu model of the leg system.

Answer]: Dry vertical a

The most well-known and practical method for designing a conceptual model of a database is the "entity-contact method", or e-r method for short, proposed in 1976. It uses the E-R model to unify the information structure of the real world in terms of entities, attributes, and the connections between entities and entities. The data flow diagram is the square fiber operation method used in the requirements analysis phase.

The database system is a kind of ideal data processing system developed to meet the needs of data processing, and it is also a software system that provides data for the actual operational storage, maintenance and application system, and is a collection of storage media, processing objects and management systems.

The database system is generally composed of four parts: the database, which is managed by the database management system, and the insertion, modification and retrieval of data are carried out through the database management system; hardware, the various physical devices that make up a computer system; software, including operating systems, database management systems and applications; A data steward who is responsible for creating, monitoring, and maintaining the entire database so that the data can be used effectively.

Features: The structure of the data, the sharing of the data is good, the independence of the data is good, the granularity of data storage is small, and the data management system provides a friendly interface for users.

The core and foundation of the database system is the data model, and the existing database system is based on a certain data model.

The core of the database system is the database management system.

A database system consists of a database, a database management system (DBMS), an application system, a database administrator, and a user. DBMS is the foundation and core of a database system.

Expansion: The basic requirements for the database system: 1. It can ensure the independence of the data. The independence of data and programs is conducive to speeding up software development and saving development costs.

2. It can ensure the reliable operation of the system and can be quickly eliminated when there is a failure; Ability to protect data from unauthorized access or destruction; Error data can be prevented, and once it is generated, it can be detected in time.

3. Have the ability to reorganize data, change the storage structure or data storage location of data, adapt to the changes in user operation characteristics, and improve the situation of data organization fragmentation and spatiotemporal performance deterioration caused by frequent insertion and deletion operations.

The database Sengao is where the data is stored. Everything in a computer, in memory, in a hard disk is data stored in a database. And the place where this data resides is called the database. It can also be called an electronic "filing cabinet".

The database in computer science and application means that the data will become larger and larger in the future, and it also means that more data will be used in the future development of the data in many science and applications.