What Are the Different Types of Federal Deductions?

The Federal Database System (FDBS) is a collection of coordinated but independent unit database (CDBS). It integrates the unit database system to different degrees, and the software that provides control and cooperative operation to the system as a whole is called the Federal Database Management System (FDBMS), a unit database can join several federal systems, each unit database system DBMS can be centralized, distributed, or another FDBMS ^[1] .

The federation database technology is proposed to achieve the interoperability of multiple databases running independently. Database systems that operate independently are often referred to as unit database systems. The so-called federated database system is a collection of unit database systems that cooperate with each other and are independent of each other. It integrates the unit database system to varying degrees. The software that provides overall control and interoperability to the system is called the Federal Database Management System. It allows database administrators to define subsets of data, which collectively form a virtual database for use by other users within the federated system.

The Federal Database System (FDBS) is a collection of coordinated but independent unit database (CDBS). It integrates the unit database system to different degrees, and the software that provides control and cooperative operation to the system as a whole is called the Federal Database Management System. (FDBMS), a unit database can join several federated systems, each unit database system DBMS can be centralized, distributed, or another FDBMS.

The architecture of the federated database is shown below

A federated database system is one of many database systems. Multi-database systems can be classified according to their design, communication, and implementation. The differences in the design of a multi-database system are reflected in the component database system's ability to choose its own design scheme, including the choice of managed data, the choice of data expression, semantics, restrictions, operations and sharing methods, and the choice of implementation methods The ability of the database management system to decide whether to communicate with other parts of the database management system is different. The performance of the parts database management system is not affected by external operations and the ability to perform local operations and the ability to determine the order of external operations. The following figure is about classification Schematic

The most important feature of the federal database system FDBS is that a unit database system can participate in the activities of the federal system while continuing local operations. The integration of the unit DBS can be managed by the users of the federated system, or it can be jointly managed by the administrator of the federated system and the administrator of the unit DBS. The degree of overall system integration depends on the requirements of the users of the federated system, depends on joining the federated system and shares Requirements for administrators of the cells of the Federal System Database. Containing a variety of database systems, its characteristics are also reflected in the four aspects of distribution, heterogeneity, independence and transparency.

The following figure

Shown is the reference structure of the federal database system, which divides the processing program into four categories-each category performs different functions for data operation commands and accessed data, and in order to deal with the distribution, heterogeneity and independence of FDBS, A five-level mode structure different from the centralized standard three-level mode structure mode, internal mode, and external mode is proposed. As can be seen from the figure, the system structure of FDBS consists of a 5-level mode, which is called a 5-level mode structure. These modes are organically combined with corresponding processors to form a complete federated system. As can be seen from the figure, the federation mode is the core of the federated database system. It is not only the integration of the output modes of multiple member libraries, but also the basis of external modes. The functions and the meaning of each mode are briefly explained.

Federal Database Processor

A processor is a software module used to manipulate commands and process data. The various data management structures differ in the types of processors they can provide and the relationships between them. There are generally four types of processor conversion processors, filter processors, construction processors, and access processors. Each class processes data manipulation commands and data differently.

Conversion processor

The conversion processor converts commands from one language source language to commands from another language target language, or converts data from one format source format to another format target format. The transformation processor can provide a data independence called data model transparency. Through it, the data structures and commands used by one processor are invisible to other processors. Data model transparency hides the differences between query language and data format.

Filter processor

Filter processors restrict commands and data passed to other processors. Associated with each filtering processor is a mapping describing commands and data constraints. These constraints are either programmed in filter processor logic or stored in separate data structures. Examples of filtering processors are syntax constraint checkers, semantic consistency constraint checkers, access controllers, etc.

Construction processor

The construction processor decomposes or copies the commands submitted by a single processor into commands that can be accepted by two or more other processors. It also combines data generated by multiple processors into a single data set for use by another single processor. Since the processor that submits the command does not need to know the location, distribution, and number of processors involved in processing the submitted command, the processor is constructed to support location, distribution, and replica transparency. The tasks that the construction processor can handle are pattern integration, query command decomposition and optimization, and global transaction management.

Access processor

The access processor is responsible for accepting commands and providing data by performing corresponding operations on the database. It may accept commands from multiple processors and interleave them. The problems involved in accessing the processor are mainly local concurrency control, commit protocol, backup and recovery.

Federated database five-tier model

The traditional centralized DBS has a standard three-tier model architecture, the so-called internal model, conceptual model, and external model. It is extended to five layers in the federal database system to meet the requirements of distribution, autonomy and heterogeneity in FDBS. These five layers include

Local schema

This is a conceptual model of the component DBS. The local model is expressed by the local data model of the component DBMS. So different local patterns can be expressed with different data models.

Component schema

By translating local patterns into the common data model of FDBS-derived component patterns, there are two reasons for defining component patterns:

• They have a single expression to describe different local patterns.

• Missing semantics in local patterns can be added to its component patterns

Thus, the component model makes it easy to implement the negotiation and integration that is performed when tight coupling is developed. Similarly, they also make the negotiation and specification of view views and multi-database queries in loosely coupled FDBS easy to implement.

The pattern translation process from the local pattern to the component pattern produces mappings between the component pattern object and the local pattern object. The conversion class processor here uses these mappings to convert the commands on the component pattern to the corresponding local pattern. Commands, such conversion-type processors and component modes support the heterogeneous nature of FDBS.

Export schema

The output mode represents a subset of the data in the membership mode that can be used by the federation and may also include different access control information about specific federated users. The purpose of defining the output mode is to facilitate the control and management of related autonomy. A filter-type processor can be used to provide the access control specified in the output mode. It limits the ability to be submitted to the corresponding component mode. A set of allowable operations, such filtering-type processors and output modes support FDBS autonomy.

Federated schema

Federated mode is the integration of multiple output modes. The federation mode also includes information about the data distribution, which is generated when the output mode is integrated. Some systems use so-called distributed mode or distribution mode to contain this information. A construction class processor is used to convert commands above the federation mode to commands on one or more output modes. This construction class processor and federation mode Supports the distribution characteristics of FDBS.

External schema

External mode defines the mode for users or a class of users and / or applications or a type of application. A filtering class processor analyzes the commands added to the external mode to ensure that they comply with the access control and integration restrictions of the federated mode.