Mumbai University > Information Technology > Sem 5 > Advanced Database Management System

Marks: 10M

Year: Dec 2015

Metadata

Metadata is simply defined as data about data. The data that are used to represent other data is known as metadata. For example, the index of a book serves as a metadata for the contents in the book. In other words, we can say that metadata is the summarized data that leads us to the detailed data.

In terms of data warehouse, we can define metadata as following:

• Metadata is a road-map to data warehouse.
• Metadata in data warehouse defines the warehouse objects.
• Metadata acts as a directory. This directory helps the decision support system to locate the contents of a data warehouse.

Metadata Repository

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.