Wiki: 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. A namespace ensures that all the identifiers within it have unique names so that they can be easily identified. Prominent examples include:

• file systems are namespaces that assign names to files;
• some programming languages organize their variables and subroutines in namespaces;
• computer networks and distributed systems assign names to resources, such as computers, printers, web sites, (remote) files, etc.
• operating systems can partition kernel resources (process IDs, users, network sockets) by isolated namespaces to support virtualization containers

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 the first names of family members are unique only within each family, 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.