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Syntaxes

The syntax for an attribute defines the storage representation, byte ordering, and matching rules for comparisons of property types. Whether the attribute value must be a string, a number, or a unit of time is also defined. Every attribute of every object is associated with exactly one syntax. The syntaxes are not represented as objects in the schema, but they are programmed to be understood by Active Directory. The allowable syntaxes in Active Directory are predefined. You cannot add new syntaxes.

When you define a new attribute, you must specify both the attributeSyntax and the oMSyntax numbers of the syntax you want for the attribute. The attributeSyntax number is an object identifier and oMSyntax number is an integer. The oMSyntax is defined by the XOM specification. This model provides a relatively fine-grained definition of syntax. For example, there are distinct oMSyntax attributes to distinguish among several types of printable strings, according to factors such as the supported character set and whether case is significant. Table 4.4 is a list of the valid syntaxes for attributes in the Active Directory schema.

Table   4.4 Valid Syntaxes for Attributes in the Active Directory Schema

Syntax 1

attribute Syntax

oM Syntax

ASN 1-Encoded Object Identifier

Description

Undefined

2.5.5.0

 

\x550500

Not a legal syntax.

Object(DN-DN)

2.5.5.1

127

\x550501

The fully qualified name of an object in the directory.

String(Object-Identifier)

2.5.5.2

6

\x550502

The object identifier.

Case-Sensitive String

2.5.5.3

27

\x550503

General String.
Differentiates uppercase and lowercase.

CaseIgnoreString(Teletex)

2.5.5.4

20

\x550504

Teletex. Does not differentiate uppercase and lowercase.

String(Printable), String(IA5)

2.5.5.5

19, 22

\x550505

Printable string or IA5-String.
Both character sets are case-sensitive.

String(Numeric)

2.5.5.6

18

\x550506

A sequence of digits.

Object(DN-Binary)

2.5.5.7

127

\x550507

A distinguished name plus a binary large object.

Boolean

2.5.5.8

1

\x550508

TRUE or FALSE values.

Integer, Enumeration

2.5.5.9

2, 10

\x550509

A 32-bit number or enumeration.

String(Octet)

2.5.5.10

4

\x55050A

A string of bytes.

String(UTC-Time), String(Generalized-Time)

2.5.5.11

23, 24

\x55050B

UTC Time or Generalized-Time.

String(Unicode)

2.5.5.12

64

\x55050C

Unicode string.

Object(Presentation-Address)

2.5.5.13

127

\x55050D

Presentation address.

Object(DN-String)

2.5.5.14

127

\x55050E

A DN-String plus a Unicode string.

String(NT-Sec-Desc)

2.5.5.15

66

\x55050F

A Microsoft® Windows NT® Security descriptor.

LargeInteger

2.5.5.16

65

\x550510

A 64-bit number.

String(Sid)

2.5.5.17

4

\x550511

Security identifier (SID).

1 The oMSyntax names are specified against the syntax numbers to enable correct choice.

note-icon Note

A complete syntax specification consists of both the attribute-syntax and the oMSyntax . Whenever more than one oMSyntax can be used with an attribute-syntax, the correct oMSyntax must be used.

Active Directory does not currently enforce character set restrictions for string syntaxes, so if you use attributes with string syntax, use only characters in the standard character set.

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