"Bi thing" meta data (metadata)

Data about Data Warehouse, refers to the data source definition, target definition, transformation rules and other related key data generated in the process of data warehouse construction. The metadata also contains business information about the meaning of the data, all of which should be properly preserved and managed well. It is convenient for the development and use of data Warehouse.
Data about data that is used to construct, maintain, manage, and use data warehouses is particularly important in the data warehouse.
The structure model of data and applications in different OLAP components. Metadata describes such objects as tables in the OLTP database, data warehouses, and cubes in the Data mart, and also records which applications reference different block of records.

The importance of the telephone yellow Pages is reflected when it comes to understanding the business and the services it provides. Metadata (Metadata) is similar to the telephone yellow pages.

• Definition of meta-data

The metadata for a data warehouse is data about the data in the Data Warehouse. It acts like a data dictionary of a database management system, preserving information such as logical data structures, files, addresses, and indexes. Broadly speaking, in the Data Warehouse, metadata describes the structure of data in the data warehouse and the method of building data.
Meta data is an important part of data Warehouse management system, metadata Manager is the key component in Enterprise Data Warehouse, which is the whole process of data warehouse construction, which directly affects the construction, use and maintenance of data Warehouse.
(1) One of the main steps in building a data warehouse is ETL. Metadata will play an important role in defining the mapping of the source data system to the Data warehouse, the rules of the data transformation, the logical structure of the Data warehouse, the rules of data updating, the history of data import and the loading cycle, and other related contents. Data extraction and transformation specialists and data Warehouse administrators are building data warehouses efficiently through metadata.
(2) When using the Data Warehouse, the user accesses the data through metadata, clarifies the meaning of the data item and customizes the report.
(3) The size and complexity of the data warehouse cannot be separated from the proper metadata management, including adding or removing external data sources, changing data cleansing methods, controlling error queries, and scheduling backups.
Meta data can be divided into technical metadata and business metadata. Technical metadata is used by IT staff to develop and manage data warehouses that describe data related to the development, management, and maintenance of data warehouses, including data source information, data transformation descriptions, data Warehouse models, data cleansing and updating rules, data mapping, and access rights. Business metadata, which serves management and business analysts, describes data from a business perspective, including business terminology, what data is in the Data Warehouse, the location of data, and the availability of data, to help business people better understand what data in the Data warehouse is available and how it is used.
From the above, metadata not only defines the patterns, sources, extraction and transformation rules of data in Data Warehouse, but also is the foundation of the whole data Warehouse system operation, and the metadata links the loose components in the Data Warehouse system, which makes up an organic whole.

• How meta data is stored

There are two common ways to store metadata: one is based on a dataset, each data set has a corresponding metadata file, each metadata file contains metadata content for the corresponding dataset, and the other is a database-based, meta-database. Where a metadata file consists of several items, each item represents a feature of the metadata, and each record is the metadata content of the dataset. The above storage methods have advantages and disadvantages, the first method of storage is to call the data when the corresponding metadata is transferred as a separate file, relative to the database has a strong independence, in the meta-data retrieval can take advantage of the function of the database, you can also transfer metadata files to other database system operation The deficiency is that if each dataset corresponds to a metadata document, there will be a large number of metadata files in the large database, which is not easy to manage. In the second storage mode, there is only one metadata file in the meta-database, which is convenient to manage and add or delete datasets, as long as the corresponding record entries are added or deleted in the file. When retrieving metadata for a dataset, the user system is required to accept this particular form of data because it is only a single record of the relational tabular data that is actually obtained. Therefore, the way to use the metabase is recommended.
The meta-database is used to store metadata, so the meta-database is best chosen by the mainstream relational database management system. The metabase also contains mechanisms for manipulating and querying metadata. The main benefit of establishing a meta-database is to provide a unified data structure and business rules, and to easily integrate multiple data marts within the enterprise. At present, some enterprises tend to build multiple data marts, rather than a centralized data warehouse, you can consider the establishment of a data warehouse (or data mart) before the establishment of a database to describe the data, service application integration, the initial support for the implementation of the Data Warehouse, the subsequent development and maintenance of a great help. The meta-database ensures the consistency and accuracy of data warehouse data, and provides the basis for enterprise data quality management.

• The role of Meta data

In the Data Warehouse, the main role of metadata is as follows.
(1) Describe what data is in the Data warehouse and help decision-makers locate the content of the Data warehouse.
(2) Define how data is entered into the Data Warehouse as a guide for data aggregation, mapping, and cleaning.
(3) To record the working time schedule of data extraction that occurs with the business event.
(4) To record and detect the system data consistency requirements and implementation status.
(5) Assess the quality of the data.

• Meta Data classification: Technical metadata, business metadata, data Warehouse operational information. -[alex Berson etc, 1999]

Technical meta-data
Includes data warehouse data information used for Data Warehouse designers and administrators to perform data warehouse development and management tasks. Including:

1. Data source information
2. Conversion description (mapping method from the operational database to the Data warehouse, and the algorithm for transforming the data)
3. Warehouse object and data structure definition for target data
4. Rules for data cleansing and data addition
5. Data map Operations
6. Access rights, backup history, archive history, information transfer history, data acquisition history, data access, etc.

Business meta Data

1. Information that is easy to understand for the user, including:
2. Topic areas and types of information objects, including queries, reports, images, audio, video, and more
3. Internet home
4. Support Data Warehouse for other information, such as information transmission system including appointment information, scheduling information, transmission target detailed description, business query object, etc.

Data Warehouse Operational information
For example, Data history (snapshot, Version), ownership, extracted audit trails, data usage

Qa:
"Metadata is the data that describes the data", which creates a recursive definition, like asking where Xiao Qiang lives, answer, next to Wang Choi. According to this definition, what is the data that the metadata describes? or meta-data. This can be a meta-element ... Meta data. I have also heard of a meta-data, if the data is a drawer file, then the metadata is classified label. What is the difference between it and the index?

"Bi thing" meta data (metadata)