《数据库系统概念》第7版第一章的review terms

Review Terms

Database-management system (DBMS) ：A collection of interrelated data and a set of programs to access those data.

Database-system applications：A database application is a computer program whose primary purpose is entering and retrieving information from a computerized database.

Online transaction processing：A large number of users use the database, with each user retrieving relatively small amounts of data, and performing small updates. This is the primary mode of use for the vast majority of users of database applications such as those that we outlined earlier.

Data analytics：the processing of data to draw conclusions, and infer rules or decision procedures, which are then used to drive business decisions.

File-processing systems：In computing, a file system or file-processing system controls how data is stored and retrieved.

Data inconsistency：Data inconsistency is a condition that occurs between files when similar data is kept in different formats in two different files, or when matching of data must be done between files.

Consistency constraints：Consistency in database systems refers to the requirement that any given database transaction must change affected data only in allowed ways. Any data written to the database must be valid according to all defined rules, including constraints, cascades, triggers, and any combination thereof.

Data abstraction：Data abstraction enforces a clear separation between the abstract properties of a data type and the concrete details of its implementation.

Physical level：The lowest level of abstraction describes how the data are actually stored. The physical level describes complex low-level data structures in detail.

Logical level：The next-higher level of abstraction describes what data are stored in the database, and what relationships exist among those data. The logical level thus describes the entire database in terms of a small number of relatively simple structures.

View level：The highest level of abstraction describes only part of the entire database. Even though the logical level uses simpler structures, complexity remains because of the variety of information stored in a large database. Many users of the database system do not need al this information; instead, they need to access only a part of the database. The view level of abstraction exists to simplify their interaction with the system. The system may provide many views for the same database.

Instance：The collection of information stored in the database at a particular moment.

Schema：The overall design of the database.

Physical schema：The physical schema describes tl he database design at the physical level. physical schema is a term used in data management to describe how data is to be represented and stored (files, indices) in secondary storage using a particular database management system (DBMS).

Logical schema：logical schema is a data model of a specific problem domain expressed independently of a particular database management product or storage technology (physical data model) but in terms of data structures such as relational tables and columns, object-oriented classes, or XML tags.

Subschema：A database may also have several schemas at the view level sometimes called subschemas, that describe different views of the database.

Physical data independence：: The ability to change the physical schema wit