A specific explanation of metadata

I got this from wikipedia. Sharing with you all.

Metadata (meta data, or sometimes metainformation) is "data about other data", of any sort in any media. An item of metadata may describe an individual datum, or content item, or a collection of data including multiple content items and hierarchical levels, for example a database schema. In data processing, metadata provides information about, or documentation of, other data managed within an application or environment. This commonly defines the structure or schema of the primary data.
For example, metadata would document data about data elements or attributes, (name, size, data type, etc) and data about records or data structures (length, fields, columns, etc) and data about data (where it is located, how it is associated, ownership, etc.). Metadata may include descriptive information about the context, quality and condition, or characteristics of the data. It may be recorded with high or low granularity.

Chapter 7 is talking about metadata for the knowledge structure, which I thought is one of the key features of web 2.0. For me web 2.0 is not just social network, communication, etc, it also refers to the convenient information achievement. Using the tag, hyperlink, and other bookmarks could facilitate the information getting. This is also the benefit of web 2.0.
In this fast-speed society, time-saving is a component to ensure success. Web 2.0 probives an opportunity and help to reduce the time spending on information gathering.
I do believe web 2.0 could help the society develop.