X.500

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X.500

(standard, networking)
The set of ITU-T standards covering electronic directory services such as white pages, Knowbot, whois.

Compare: LDAP.
This article is provided by FOLDOC - Free Online Dictionary of Computing (foldoc.org)

X.500

An OSI protocol for managing online directories of users and resources. X.500 can be used to support X.400 and other messaging systems, but it is not restricted to email usage. It provides a hierarchical structure that fits the world's classification system: countries, states, cities, streets, houses, families, etc. The goal is a global directory.

The DIB, DSA and DCA
An X.500 directory is called a "Directory Information Base" (DIB) or white pages. The program that maintains the DIBs is called a "Directory Server Agent" (DSA). A Directory Client Agent (DCA) is used to search DSA sites for names and addresses.

Replication and Access Control
Published in 1988, the 1993 edition of X.500 added replication and access control. Using the Directory Information Shadowing Protocol (DISP), replication allows a portion of the Directory Information Tree (DIT) to be copied between nodes. Access control allows or denies access to a particular attribute of a directory entry based on the identity of the requesting user. See X.400.
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The Fiat Chrysler Automobil's showroom is on 682 sqm, divided into four pavilions: Fiat Tipo, Fiat X500, the award-winning Alfa Romeo (featuring Stelvio, Alfa Romeo Giulia, and Alfa Romeo Giulietta), and, finally, Jeep, which will feature Jeep Renegade and Jeep Grand Cherokee.
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To examine the areas of interest, the specimens were imaged with a voltage of 20-25 kVp and at a magnification range of x15 to x2500 (x15, x50, x100, x200, x500, x1000 and x2500).
Caption: Figure 2: SEM images of 3 studied scaffolds at 2 magnifications (x100 and x500): (a1, a2) S scaffold, (b1, b2) A scaffold, and (c1, c2) SA scaffold.
TEM observations were conducted at three different magnifications with x6,000, x20,000 and x500,000 [29].
D, T-cell receptor pF1 showing diffuse coexpression with the [CD8.sup.+] population (original magnifications X100 [A] and X500 [C]; original magnification X100 [B and D]).
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Precision microscopes were used to measure the indentations which usually have a magnification of around x500 and measure to an accuracy of [+ or -] 0.5 micrometres
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