Global Name Service (GNS)
Designed
and implemented by Lampson and colleagues at the DEC Systems Research Center
(1986)
Provide
facilities for resource location, email addressing and authentication
When the
naming database grows from small to large scale, the structure of name space
may change
the
service should accommodate it
Cache
consistency ?
The GNS
manages a naming database that is composed of a tree of directories holding
names and values. Directories are named by multi-part pathnames referred to a
root, or relative to a working directory, much like file names in a UNIX file
system. Each directory is also assigned an integer, which serves as a unique directory identifier (DI). A directory
contains a list of names and references. The values stored at the leaves of the
directory tree are organized into value
trees, so that the attributes associated with names can be structured
values.
Names in
the GNS have two parts: <directory
name, value name>. The first
part identifies a directory; the second refers to a value tree, or some portion
of a value tree.
GNS Structure
Tree of
directories holding names and values
Muti-part
pathnames refer to the root or relative working directory (like Unix file
system)
Unique
Directory Identifier (DI)
A
directory contains list of names and references
Leaves of
tree contain value trees (structured values)
GNS directory tree and value tree
Accommodating changes
How to
integrate naming trees of two previously separate GNS services But what is for ‘/UK/AC/QMV, Peter.Smith’ ?
Using DI to solve changes
Using the
name ‘#599/UK/AC/QMV, Peter.Smith’
Restructuring of database
Using
symbolic links
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