Namespace

In computing, a namespace is a set of symbols that are used to organize objects of various kinds, so that these objects may be referred to by name. Prominent examples include:

Namespaces are commonly structured as hierarchies to allow reuse of names in different contexts. As an analogy, consider a system of naming of people where each person has a proper name, as well as a family name shared with their relatives. If, in each family, the names of family members are unique, then each person can be uniquely identified by the combination of first name and family name; there is only one Jane Doe, though there may be many Janes. Within the namespace of the Doe family, just "Jane" suffices to unambiguously designate this person, while within the "global" namespace of all people, the full name must be used.

In a similar way, hierarchical file systems organize files in directories. Each directory is a separate namespace, so that the directories "letters" and "invoices" may both contain a file "to_jane".

In computer programming, namespaces are typically employed for the purpose of grouping symbols and identifiers around a particular functionality and to avoid name collisions between multiple identifiers that share the same name.

In networking, the Domain Name System organizes websites (and other resources) into hierarchical namespaces.

Element names are defined by the developer. This often results in a conflict when trying to mix XML documents from different XML applications.

This XML carries HTML table information:

This XML carries information about a table (i.e. a piece of furniture):

If these XML fragments were added together, there would be a name conflict. Both contain a <table> element, but the elements have different content and meaning.

An XML parser will not know how to handle these differences.

Name conflicts in XML can easily be avoided using a name prefix.

The following XML distinguishes between information about the HTML table and furniture by prefixing "h" and "f" at the beginning xml/xml_namespaces.asp

A name in a namespace consists of a namespace identifier and a local name. The namespace name is usually applied as a prefix to the local name.

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