METADATA
98.What is meant by metadata in context of a Datawarehouse and how it is important?
Meta data is the data about data; Business Analyst or data modeler usually capture information about data
- source (where and how the data is originated),
- nature of data (char, varchar, nullable, existance, valid values etc)
- and behavior of data (how it is modified / derived and the life cycle ) in data dictionary a.k.a metadata.
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metadata is the summarized data that leads us to the detailed data.
Metadata is also presented at the Datamart level, subsets, fact and dimensions, ODS etc. For a DW user,metadata provides vital information for analysis / DSS.
99.What is the difference between metadata and data dictionary?
- Metadata is defined as data about the data. But, Data dictionary contain the information about the project information, graphs, abinito commands and server information
- Metadata repository is an integral part of a data warehouse system. It contains the following metadata −
- Business metadata − It contains the data ownership information, business definition, and changing policies.
- Operational metadata − It includes currency of data and data lineage. Currency of data refers to the data being active, archived, or purged. Lineage of data means history of data migrated and transformation applied on it.
- Data for mapping from operational environment to data warehouse − It metadata includes source databases and their contents, data extraction, data partition, cleaning, transformation rules, data refresh and purging rules.
- The algorithms for summarization − It includes dimension algorithms, data on granularity, aggregation, summarizing, etc.
Categories of Metadata
Metadata can be broadly categorized into three categories −
- Business Metadata − It has the data ownership information, business definition, and changing policies.
- Technical Metadata − It includes database system names, table and column names and sizes, data types and allowed values. Technical metadata also includes structural information such as primary and foreign key attributes and indices.
- Operational Metadata − It includes currency of data and data lineage. Currency of data means whether the data is active, archived, or purged. Lineage of data means the history of data migrated and transformation applied on it.
100.What does Metadata Respiratory contain?
- definition of data warehouse
- business metadata
- operational metadata
- data for mapping from operational environment to data warehouse
- and the algorithms for summarization
- Definition of data warehouse − It includes the description of structure of data warehouse. The description is defined by schema, view, hierarchies, derived data definitions, and data mart locations and contents.
- Business metadata − It contains has the data ownership information, business definition, and changing policies.
- Operational Metadata − It includes currency of data and data lineage. Currency of data means whether the data is active, archived, or purged. Lineage of data means the history of data migrated and transformation applied on it.
- Data for mapping from operational environment to data warehouse − It includes the source databases and their contents, data extraction, data partition cleaning, transformation rules, data refresh and purging rules.
- Algorithms for summarization − It includes dimension algorithms, data on granularity, aggregation, summarizing, etc.