定义查询过滤器（Search Filter Definition）：

filter     = "(" filtercomp ")"
        filtercomp = and / or / not / item
        and        = "&" filterlist
        or         = "|" filterlist
        not        = "!" filter
        filterlist = 1*filter
        item       = simple / present / substring / extensible
        simple     = attr filtertype value
        filtertype = equal / approx / greater / less
        equal      = "="
        approx     = "~="
        greater    = ">="
        less       = "<="
        extensible = attr [":dn"] [":" matchingrule] ":=" value
                     / [":dn"] ":" matchingrule ":=" value
        present    = attr "=*"
        substring  = attr "=" [initial] any [final]
        initial    = value
        any        = "*" *(value "*")
        final      = value
        attr       = AttributeDescription from Section 4.1.5 of [1]
        matchingrule = MatchingRuleId from Section 4.1.9 of [1]
        value      = AttributeValue from Section 4.1.6 of [1]

The attr, matchingrule, and value constructs are as described in the
   corresponding section of [1] given above.

   If a value should contain any of the following characters

           Character       ASCII value
           ---------------------------
           *               0x2a
           (               0x28
           )               0x29
           \               0x5c
           NUL             0x00


示例：





This section gives a few examples of search filters written using
   this notation.

        (cn=Babs Jensen)
        (!(cn=Tim Howes))
        (&(objectClass=Person)(|(sn=Jensen)(cn=Babs J*)))
        (o=univ*of*mich*)

   The following examples illustrate the use of extensible matching.

        (cn:1.2.3.4.5:=Fred Flintstone)
        (sn:dn:2.4.6.8.10:=Barney Rubble)
        (o:dn:=Ace Industry)
        (:dn:2.4.6.8.10:=Dino)