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In addition to defining what data can be stored as the value of an attribute, an
attribute syntax also defines how those values behave during searches and other
directory operations. This is done using syntax and matching rules. The attribute
telephoneNumber, for example, might have a syntax that specifies:
► Lexicographic ordering.
► Case, spaces, and dashes are ignored during the comparisons.
► Values must be character strings.
For example, using the correct definitions, the telephone numbers
123-456-7890, 123456-7890, and 1234567890 are considered to be the same. A
few of the common syntaxes and matching rules, defined in RFC 4517, are listed
in Table 12-5.
Table 12-5 Examples of LDAP syntaxes
Syntaxes and
matching rules
Description
Bit String A sequence of binary digits
Postal Address A sequence of strings that form an address in a physical mail
system
caseExactMatch A matching rule requiring that string comparisons are
case-sensitive
caseIgnoreMatch A matching rule that does not require case-sensitive
comparisons
Table 12-6 lists some common attributes defined by RFC 4519. Some attributes
have alias names that can be used wherever the full attribute name is used.
Table 12-6 Examples of LDAP syntaxes
Attribute, alias Syntax Description Example
commonName, cn cis Common name of an entry John Smith
surname, sn cis A person’s last name Smith
initials cis A person’s initials JS
telephoneNumber tel A person’s telephone number 123-456-7890
An object class is a general description, sometimes called a template, of an
object type, as opposed to the description of a specific object of that type. For
example, the object class person has a surname attribute, while the object
describing John Smith has a surname attribute with the value Smith. The object
Chapter 12. Directory and naming protocols 465