A.  An Algorithm for Resolving Time Switches

   The following algorithm determines whether a given instant falls
   within a repetition of a "time-switch" recurrence.  If the pre-
   processing described in Section 4.4.1 has been done, it operates in
   constant time.  Open-source Java code implementing this algorithm is
   available at http://www.cs.columbia.edu/~lennox/Cal-Code/ on the
   world wide web.

   This algorithm is believed to be correct, but this section is non-
   normative.  Section 4.4, and RFC 2445 [8], are the definitive
   definitions of recurrences.

      1. Compute the time of the call, in the timezone of the time
         switch.

      2. If the call time is earlier than "dtstart", fail NOMATCH.

      3. If the call time is less than "duration" after dtstart, succeed
         MATCH.

      4. Determine the smallest unit specified in a "byxxx" rule or by
         the "freq."  Call this the Minimum Unit.  Determine the
         previous instant (before or equal to the call time) when all
         the time units smaller than the minimum unit are the same as
         those of "dtstart."  If the minimum unit is a second, this time
         is the same as the instant.  If the minimum unit is a minute or
         an hour, the minutes or the minutes and hours, respectively,
         must be the same as "dtstart".  For all other minimum units,
         the time-of-day must be the same as "dtstart."  If the minimum
         unit is a week, the day-of-the-week must be the same as
         "dtstart."  If the minimum unit is a month, the day-of-the-
         month must be the same as "dtstart."  If the minimum unit is a
         year, the month and day-of-month must both be the same as
         "dtstart."  (Note that this means it may be necessary to roll
         back more than one minimum unit -- if the minimum unit is a
         month, then some months do not have a 31st (or 30th or 29th)
         day; if the minimum unit is a year, then some years do not have
         a February 29th.  In the Gregorian calendar, it is never
         necessary to roll back more than two months if the minimum unit
         is a month, or eight years if the minimum unit is a year.
         Between 1904 and 2096, it is never necessary to roll back more
         than four years -- the eight-year rollback can only occur when
         the Gregorian calendar "skips" a leap year.

         Call this instant the Candidate Start Time.

      5. If the time between the candidate start time and the call time
         is more than the duration, fail NOMATCH.

      6. If the candidate start time is later than the "until" parameter
         of the recurrence (or the virtual "until" computed off-line
         from "count"), fail NOMATCH.

      7. Call the unit of the "freq" parameter of the recurrence the
         Frequency Unit.  Determine the frequency unit enclosing the
         Candidate Start Time, and that enclosing "dtstart".  Calculate
         the number of frequency units that have passed between these
         two times.  If this is not a multiple of the "interval"
         parameter, fail NOMATCH.

      8. For every "byxxx" rule, confirm that the candidate start time
         matches one of the options specified by that "byxxx" rule.  If
         so, succeed MATCH.

      9. Calculate a previous candidate start time.  Repeat until the
         difference between the candidate start time and the call time
         is more than the duration.  If no candidate start time has been
         validated, fail NOMATCH.

B.  Suggested Usage of CPL with H.323

   This appendix gives a suggested usage of CPL with H.323 [16].   Study
   Group 16 of the ITU, which developed H.323, is proposing to work on
   official CPL mappings for that protocol.  This section is therefore
   not normative.

B.1.  Usage of "address-switch" with H.323

   Address switches are specified in Section 4.1.  This section
   specifies the mapping between H.323 messages and the fields and
   subfields of address-switches.

   For H.323, the "origin" address corresponds to the alias addresses in
   the "sourceAddress" field of the "Setup-UUIE" user-user information
   element, and to the Q.931 [23] information element "Calling party
   number."  If both fields are present, or if multiple alias addresses
   for "sourceAddress" are present, which one has priority is a matter
   of local server policy; the server SHOULD use the same resolution as
   it would use for routing decisions in this case.  Similarly, the
   "destination" address corresponds to the alias addresses of the
   "destinationAddress" field, and to the Q.931 information element
   "Called party number."

   The "original-destination" address corresponds to the "Redirecting
   number" Q.931 information element, if it is present; otherwise it is
   the same as the "destination" address.

   The mapping of H.323 addresses into subfields depends on the type of
   the alias address.  An additional subfield type, "alias-type", is
   defined for H.323 servers, corresponding to the type of the address.
   Possible values are "dialedDigits", "h323-ID", "url-ID",
   "transportID", "email-ID", "partyNumber", "mobileUIM", and "Q.931IE".
   If future versions of the H.323 specification define additional types
   of alias addresses, those names MAY also be used.

   In versions of H.323 prior to version 4, "dialedDigits" was known as
   "e164".  The two names SHOULD be treated as synonyms.

   The value of the "address-type" subfield for H.323 messages is "h323"
   unless the alias type is "url-ID" and the URL scheme is something
   other than h323; in this case the address-type is the URL scheme, as
   specified in Section 4.1.1 for SIP.

   An H.323-aware CPL server SHOULD map the address subfields from the
   primary alias used for routing.  It MAY also map subfields from other
   aliases, if subfields in the primary address are not present.

   The following mappings are used for H.323 alias types:

      dialedDigits, partyNumber, mobileUIM, and Q.931IE: the "tel" and
           "user" subfields are the string of digits, as is the
           "entire-address" form.  The "host" and "port" subfields are
           not present.

      url-ID: the same mappings are used as for SIP, in Section 4.1.1.

      h323-ID: the "user" field is the string of characters, as is the
           "entire-address" form.  All other subfields are not present.

      email-ID: the "user" and "host" subfields are set to the
           corresponding parts of the e-mail address.  The "port" and
           "tel" subfields are not present.  The "entire-address" form
           corresponds to the entire e-mail address.

      transportID: if the TransportAddress is of type "ipAddress,"
           "ipSourceRoute," or "ip6Address," the "host" subfield is set
           to the "ip" element of the sequence, translated into the
           standard IPv4 or IPv6 textual representation, and the "port"
           subfield is set to the "port" element of the sequence
           represented in decimal.  The "tel" and "user" fields are not
           present.  The "entire-address" form is not defined.  The

           representation and mapping of transport addresses is not
           defined for non-IP addresses.

   H.323 [16] defines an "h323" URI scheme.  This appendix defines a
   mapping for these URIs onto the CPL "address-switch" subfields, as
   given in Section 4.1.  This definition is also available as RFC 3508
   [24], which is an excerpt from the H.323 specification.

   For h323 URIs, the "user", "host", and "port" subfields are set to
   the corresponding parts of the H.323 URL.  The "tel" subfield is not
   present.  The "entire-address" form corresponds to the entire URI.

   This mapping MAY be used both for h323 URIs in an h323 "url-ID"
   address alias, and for h323 URIs in SIP messages.

B.2.  Usage of "string-switch" with H.323

   For H.323, the "string-switch" node (see Section 4.2) is used as
   follows.  The field "display" corresponds to the Q.931 information
   element of the same name, copied verbatim.  The fields "subject",
   "organization", and "user-agent" are not used and are never present.

      The "display" IE is conventionally used for Caller-ID purposes, so
      arguably it should be mapped to the "display" subfield of an
      "address-match" with the field "originator".  However, since a) it
      is a message-level information element, not an address-level one,
      and b) the Q.931 specification [23] says only that "[t]he purpose
      of the Display information element is to supply display
      information that may be displayed by the user," it seems to be
      more appropriate to allow it to be matched in a "string-switch"
      instead.

B.3.  Usage of "language-switch" with H.323

   The language-ranges for the "language-switch" switch are obtained
   from the H.323 UUIE "language".  The switch is not-present if the
   initial message did not contain this UUIE.

B.4.  Usage of "priority-switch" with H.323

   All H.323 messages are considered to have priority "normal" for the
   purpose of a priority switch (see Section 4.5).

B.5.  Usage of "location" with H.323

   Locations in explicit location nodes (Section 5.1) are specified as
   URLs.  Therefore, all locations added in this manner are interpreted
   as being of alias type "url-ID" in H.323.

   Specifications of other H.323 address alias types will require a CPL
   extension (see Section 11).

B.6.  Usage of "lookup" with H.323

   For location lookup nodes (Section 5.2), the "registration" lookup
   source corresponds to the locations registered with the server using
   "RAS" messages.

B.7.  Usage of "remove-location" with H.323

   Location removal nodes (Section 5.3) remove addresses with the alias
   type "url-ID" using verbatim string matching on the URLs.  If a "tel"
   URL is specified as the location, matching addresses (ignoring visual
   separators) with the alias types "dialedDigits" ("e164"),
   "partyNumber", "mobileUIM", or "Q.931IE" are also removed.  No
   mechanism is provided to remove other alias types.

C.  The XML Schema for CPL

   This section includes a full XML Schema describing the XML syntax of
   CPL.   Every script submitted to a CPL server SHOULD comply with this
   XML Schema.   When parsing scripts comply with the CPL DTD in earlier
   documents, the DOCTYPE lines in the scripts should be ignored.  Note
   that compliance with this schema is not a sufficient condition for
   correctness of a CPL script, as many of the conditions described in
   this specification are not expressible in schema syntax.  Figure 31
   shows the structure of the schema.  'incoming' and 'outgoing' are
   defined as the substitutionGroup of the 'toplevelaction'.  All the
   switches are defined as the substitutionGroup of the 'switch'
   element.  All the actions are defined as the substitutionGroup of the
   'action' element.

         +---------+    +------+                    +--address
       +-+ancillary|    |switch|** +--------------+ | +-not-present
       | +---------+    +---+--+ **|address-switch+-+-+-address
       |                    |    * +--------------+ +--otherwise
       | +---------+ +----+ |    *                   +--language
       +-+subaction+-+Node| |    * +---------------+ | +-not-present
       | +---------+ +----+ |    **|language-switch|-+-+-language
       |                    |    * +---------------+ +--otherwise
       |                    |    *                   +--priority
       |                    |    * +---------------+ | +-not-present
       |                    |    **|priority-switch|-+-+-priority
       |                    |    * +---------------+ +--otherwise
       |                    |    *                 +--string
   cpl-+                    |    * +-------------+ | +-not-present
       |                    |    **|string-switch|-+ +-string
       |                    |    * +-------------+ +--otherwise
       |                    |    *               +--time
       | +--------------+ +-+--+ * +-----------+ | +-not-present
       +-+toplevelaction+-+Node|  *|time-switch|-+-+-time
         +-----*--------+ +-+--+   +-----------+ +--otherwise
              *             |              +--------+ +----+
             *              |            **|location+-|Node|
             *              | +--------+ * +--------+ +----+
             * +--------+   |-+modifier|** +------+ +-success-Node
             **|incoming|   | +--------+ *-|lookup+-+-notfound-Node
             * +--------+   |            * +------+ +-failure-Node
             *              | +---+      * +---------------+ +----+
             * +--------+   +-+Sub+-sub  **|remove-location+-+Node|
              *|outgoing|   | +---+        +---------------+ +----+
               +--------+   |            +---+
                            |          **|log+-Node
                            |          * +---+
                            |          * +----+
                            | +------+ **|mail+-Node
                            +-+action|** +----+     +-busy-Node
        ----  contains        +------+ * +-----+    |
                                       **|proxy+----+-noanswer-Node
        ****  substitutes              * +-----+    |
                                       * +--------+ +-failure-Node
                                       **|redirect| |
                                       * +--------+ +-redirection-Node
                                       * +------+   |
                                        *|reject|   +-default-Node
                                         +------+

   Figure 31: The structure of the XML schema for CPL

   BEGIN
   <?xml version="1.0" encoding="UTF-8"?>
   <xs:schema targetNamespace="urn:ietf:params:xml:ns:cpl"
     xmlns="urn:ietf:params:xml:ns:cpl"
     xmlns:xs="http://www.w3.org/2001/XMLSchema"
     elementFormDefault="qualified"
     attributeFormDefault="unqualified">
     <xs:complexType name="TopLevelActionType" abstract="true">
       <xs:group ref="Node"/>
     </xs:complexType>
     <xs:element name="toplevelaction" type="TopLevelActionType"/>
     <xs:complexType name="ActionType" abstract="true"/>
     <xs:element name="action" type="ActionType"/>
     <xs:complexType name="SwitchType" abstract="true"/>
     <xs:element name="switch" type="SwitchType"/>
     <xs:complexType name="ModifierType" abstract="true"/>
     <xs:element name="modifier" type="ModifierType"/>
     <xs:element name="location" type="LocationType"
         substitutionGroup="modifier"/>
     <xs:element name="lookup" type="LookupType"
         substitutionGroup="modifier"/>
     <xs:element name="remove-location" type="RemoveLocationType"
         substitutionGroup="modifier"/>
     <xs:element name="sub" type="SubAction"/>
     <xs:group name="Node">
       <xs:choice>
         <xs:element ref="switch" minOccurs="0" maxOccurs="1"/>
         <xs:element ref="modifier" minOccurs="0" maxOccurs="1"/>
         <xs:element ref="sub" minOccurs="0" maxOccurs="1"/>
         <xs:element ref="action" minOccurs="0" maxOccurs="1"/>
       </xs:choice>
     </xs:group>
     <xs:complexType name="OtherwiseAction">
       <xs:group ref="Node"/>
     </xs:complexType>
     <xs:complexType name="NotPresentAction">
       <xs:group ref="Node"/>
     </xs:complexType>
     <xs:simpleType name="YesNoType">
       <xs:restriction base="xs:NMTOKEN">
         <xs:enumeration value="yes"/>
         <xs:enumeration value="no"/>
       </xs:restriction>
     </xs:simpleType>
     <xs:simpleType name="StatusType">
       <xs:union>
         <xs:simpleType>
           <xs:restriction base="xs:NMTOKEN">

             <xs:enumeration value="busy"/>
             <xs:enumeration value="notfound"/>
             <xs:enumeration value="reject"/>
             <xs:enumeration value="error"/>
           </xs:restriction>
         </xs:simpleType>
         <xs:simpleType>
           <xs:restriction base="xs:string"/>
         </xs:simpleType>
       </xs:union>
     </xs:simpleType>
     <xs:simpleType name="OrderingType">
       <xs:restriction base="xs:NMTOKEN">
         <xs:enumeration value="parallel"/>
         <xs:enumeration value="sequential"/>
         <xs:enumeration value="first-only"/>
       </xs:restriction>
     </xs:simpleType>
     <xs:simpleType name="AddressFieldType">
       <xs:union>
         <xs:simpleType>
           <xs:restriction base="xs:NMTOKEN">
             <xs:enumeration value="origin"/>
             <xs:enumeration value="destination"/>
             <xs:enumeration value="original-destination"/>
           </xs:restriction>
         </xs:simpleType>
         <xs:simpleType>
           <xs:restriction base="xs:string"/>
         </xs:simpleType>
       </xs:union>
     </xs:simpleType>
     <xs:simpleType name="AddressSubfieldType">
       <xs:union>
         <xs:simpleType>
           <xs:restriction base="xs:NMTOKEN">
             <xs:enumeration value="address-type"/>
             <xs:enumeration value="user"/>
             <xs:enumeration value="host"/>
             <xs:enumeration value="port"/>
             <xs:enumeration value="tel"/>
             <xs:enumeration value="display"/>
             <xs:enumeration value="password"/>
             <xs:enumeration value="alias-type"/>
           </xs:restriction>
         </xs:simpleType>

         <xs:simpleType>
           <xs:restriction base="xs:string"/>
         </xs:simpleType>
       </xs:union>
     </xs:simpleType>
     <xs:complexType name="AddressType">
       <xs:annotation>
         <xs:documentation>Exactly one of the three attributes must
             appear</xs:documentation>
       </xs:annotation>
       <xs:group ref="Node"/>
       <xs:attribute name="is" type="xs:string" use="optional"/>
       <xs:attribute name="contains" type="xs:string" use="optional">
         <xs:annotation>
           <xs:documentation>for "display" only</xs:documentation>
         </xs:annotation>
       </xs:attribute>
       <xs:attribute name="subdomain-of" type="xs:string"
           use="optional">
         <xs:annotation>
           <xs:documentation>for "host", "tel" only</xs:documentation>
         </xs:annotation>
       </xs:attribute>
       <xs:anyAttribute namespace="##any" processContents="lax"/>
     </xs:complexType>
     <xs:complexType name="AddressSwitchType">
       <xs:complexContent>
         <xs:extension base="SwitchType">
           <xs:sequence>
             <xs:element name="address" type="AddressType" minOccurs="0"
                 maxOccurs="unbounded"/>
             <xs:sequence minOccurs="0">
               <xs:element name="not-present" type="NotPresentAction"/>
               <xs:element name="address" type="AddressType"
                   minOccurs="0" maxOccurs="unbounded"/>
             </xs:sequence>
             <xs:element name="otherwise" type="OtherwiseAction"
                 minOccurs="0"/>
           </xs:sequence>
           <xs:attribute name="field" type="AddressFieldType"
               use="required"/>
           <xs:attribute name="subfield" type="AddressSubfieldType"
               use="optional"/>
         </xs:extension>
       </xs:complexContent>
     </xs:complexType>
     <xs:element name="address-switch" type="AddressSwitchType"
         substitutionGroup="switch"/>

     <xs:simpleType name="StringFieldType">
       <xs:restriction base="xs:NMTOKEN">
         <xs:enumeration value="subject"/>
         <xs:enumeration value="organization"/>
         <xs:enumeration value="user-agent"/>
         <xs:enumeration value="display"/>
       </xs:restriction>
     </xs:simpleType>
     <xs:complexType name="StringType">
       <xs:group ref="Node"/>
       <xs:attribute name="is" type="xs:string" use="optional"/>
       <xs:attribute name="contains" type="xs:string" use="optional"/>
       <xs:anyAttribute namespace="##any" processContents="lax"/>
     </xs:complexType>
     <xs:complexType name="StringSwitchType">
       <xs:complexContent>
         <xs:extension base="SwitchType">
           <xs:sequence>
             <xs:element name="string" type="StringType" minOccurs="0"
                 maxOccurs="unbounded"/>
             <xs:sequence minOccurs="0">
               <xs:element name="not-present" type="NotPresentAction"/>
               <xs:element name="string" type="StringType" minOccurs="0"
                   maxOccurs="unbounded"/>
             </xs:sequence>
             <xs:element name="otherwise" type="OtherwiseAction"
                 minOccurs="0"/>
           </xs:sequence>
           <xs:attribute name="field" type="StringFieldType"
               use="required">
             <xs:annotation>
               <xs:documentation>Strings are matched as case-insensitive
                   Unicode strings.</xs:documentation>
             </xs:annotation>
           </xs:attribute>
         </xs:extension>
       </xs:complexContent>
     </xs:complexType>
     <xs:element name="string-switch" type="StringSwitchType"
         substitutionGroup="switch"/>
     <xs:complexType name="LanguageType">
       <xs:group ref="Node"/>
       <xs:attribute name="matches" type="xs:string" use="required">
         <xs:annotation>
           <xs:documentation>The value of one of these parameters is a
               language-tag, as defined in RFC
               3066.</xs:documentation>
         </xs:annotation>

       </xs:attribute>
       <xs:anyAttribute namespace="##any" processContents="lax"/>
     </xs:complexType>
     <xs:complexType name="LanguageSwitchType">
       <xs:complexContent>
         <xs:extension base="SwitchType">
           <xs:sequence>
             <xs:element name="language" type="LanguageType"
                 minOccurs="0" maxOccurs="unbounded"/>
             <xs:sequence minOccurs="0">
               <xs:element name="not-present" type="NotPresentAction"/>
               <xs:element name="language" type="LanguageType"
                   minOccurs="0" maxOccurs="unbounded"/>
             </xs:sequence>
             <xs:element name="otherwise" type="OtherwiseAction"
                 minOccurs="0"/>
           </xs:sequence>
         </xs:extension>
       </xs:complexContent>
     </xs:complexType>
     <xs:element name="language-switch" type="LanguageSwitchType"
         substitutionGroup="switch"/>
     <xs:simpleType name="FreqType">
       <xs:restriction base="xs:NMTOKEN">
         <xs:pattern value="[s|S][e|E][c|C][o|O][n|N][d|D][l|L][y|Y]"/>
         <xs:pattern value="[m|M][i|I][n|N][u|U][t|T][e|E][l|L][y|Y]"/>
         <xs:pattern value="[h|H][o|O][u|U][r|R][l|L][y|Y]"/>
         <xs:pattern value="[d|D][a|A][i|I][l|L][y|Y]"/>
         <xs:pattern value="[w|W][e|E][e|E][k|K][l|L][y|Y]"/>
         <xs:pattern value="[m|M][o|N][n|N][t|T][h|H][l|L][y|Y]"/>
         <xs:pattern value="[y|Y][e|E][a|A][r|R][l|L][y|Y]"/>
       </xs:restriction>
     </xs:simpleType>
     <xs:simpleType name="YearDayType">
       <xs:union>
         <xs:simpleType>
           <xs:restriction base="xs:integer">
             <xs:minInclusive value="-366"/>
             <xs:maxInclusive value="-1"/>
           </xs:restriction>
         </xs:simpleType>
         <xs:simpleType>
           <xs:restriction base="xs:integer">
             <xs:minInclusive value="1"/>
             <xs:maxExclusive value="366"/>
           </xs:restriction>
         </xs:simpleType>
       </xs:union>

     </xs:simpleType>
     <xs:simpleType name="DayType">
       <xs:restriction base="xs:NMTOKEN">
         <xs:pattern value="[m|M][o|O]"/>
         <xs:pattern value="[t|T][u|U]"/>
         <xs:pattern value="[w|W][e|E]"/>
         <xs:pattern value="[t|T][h|H]"/>
         <xs:pattern value="[f|F][r|R]"/>
         <xs:pattern value="[s|S][a|A]"/>
         <xs:pattern value="[s|S][u|U]"/>
       </xs:restriction>
     </xs:simpleType>
     <xs:complexType name="TimeType">
       <xs:annotation>
         <xs:documentation>Exactly one of the two attributes "dtend" and
             "duration" must occur.  None of the attributes following
             freq are meaningful unless freq appears.
             </xs:documentation>
       </xs:annotation>
       <xs:group ref="Node"/>
       <xs:attribute name="dtstart" type="xs:string" use="required">
         <xs:annotation>
           <xs:documentation>RFC 2445 DATE-TIME</xs:documentation>
         </xs:annotation>
       </xs:attribute>
       <xs:attribute name="dtend" type="xs:string" use="optional">
         <xs:annotation>
           <xs:documentation>RFC 2445 DATE-TIME</xs:documentation>
         </xs:annotation>
       </xs:attribute>
       <xs:attribute name="duration" type="xs:string" use="optional">
         <xs:annotation>
           <xs:documentation>RFC 2445 DURATION</xs:documentation>
         </xs:annotation>
       </xs:attribute>
       <xs:attribute name="freq" type="FreqType" use="optional"/>
       <xs:attribute name="interval" type="xs:positiveInteger"
           default="1"/>
       <xs:attribute name="until" type="xs:string" use="optional">
         <xs:annotation>
           <xs:documentation>RFC 2445 DATE-TIME</xs:documentation>
         </xs:annotation>
       </xs:attribute>
       <xs:attribute name="count" type="xs:positiveInteger"
           use="optional"/>
       <xs:attribute name="bysecond" type="xs:string" use="optional">
         <xs:annotation>
           <xs:documentation>Comma-separated list of seconds within a

               minute.  Valid values are 0 to 59.</xs:documentation>
         </xs:annotation>
       </xs:attribute>
       <xs:attribute name="byminute" type="xs:string" use="optional">
         <xs:annotation>
           <xs:documentation>Comma-separated list of minutes within an
               hour.  Valid values are 0 to 59.</xs:documentation>
         </xs:annotation>
       </xs:attribute>
       <xs:attribute name="byhour" type="xs:string" use="optional">
         <xs:annotation>
           <xs:documentation>Comma-separated list of hours of the day.
               Valid values are 0 to 23.</xs:documentation>
         </xs:annotation>
       </xs:attribute>
       <xs:attribute name="byday" type="xs:string" use="optional">
         <xs:annotation>
           <xs:documentation>Comma-separated list of days of the week.
               Valid values are "MO", "TU", "WE", "TH", "FR", "SA" and
               "SU".  These values are not case-sensitive.  Each can be
               preceded by a positive (+n) or negative (-n)
               integer.</xs:documentation>
         </xs:annotation>
       </xs:attribute>
       <xs:attribute name="bymonthday" type="xs:string" use="optional">
         <xs:annotation>
           <xs:documentation>Comma-separated list of days of the month.
               Valid values are 1 to 31 or -31 to
               -1.</xs:documentation>
         </xs:annotation>
       </xs:attribute>
       <xs:attribute name="byyearday" type="xs:string" use="optional">
         <xs:annotation>
           <xs:documentation>Comma-separated list of days of the year.
               Valid values are 1 to 366 or -366 to
               -1.</xs:documentation>
         </xs:annotation>
       </xs:attribute>
       <xs:attribute name="byweekno" type="xs:string" use="optional">
         <xs:annotation>
           <xs:documentation>Comma-separated list of ordinals specifying
               weeks of the year.  Valid values are 1 to 53 or -53 to
               -1.</xs:documentation>
         </xs:annotation>
       </xs:attribute>
       <xs:attribute name="bymonth" type="xs:string" use="optional">
         <xs:annotation>
           <xs:documentation>Comma-separated list of months of the year.

               Valid values are 1 to 12.</xs:documentation>
         </xs:annotation>
       </xs:attribute>
       <xs:attribute name="wkst" type="DayType" default="MO"/>
       <xs:attribute name="bysetpos" type="YearDayType"/>
       <xs:anyAttribute namespace="##any" processContents="lax"/>
     </xs:complexType>
     <xs:simpleType name="TZIDType">
       <xs:restriction base="xs:string"/>
     </xs:simpleType>
     <xs:simpleType name="TZURLType">
       <xs:restriction base="xs:anyURI"/>
     </xs:simpleType>
     <xs:complexType name="TimeSwitchType">
       <xs:complexContent>
         <xs:extension base="SwitchType">
           <xs:sequence>
             <xs:element name="time" type="TimeType" minOccurs="0"
                 maxOccurs="unbounded"/>
             <xs:sequence minOccurs="0">
               <xs:element name="not-present" type="NotPresentAction"/>
               <xs:element name="time" type="TimeType" minOccurs="0"
                   maxOccurs="unbounded"/>
             </xs:sequence>
             <xs:element name="otherwise" type="OtherwiseAction"
                 minOccurs="0"/>
           </xs:sequence>
           <xs:attribute name="tzid" type="TZIDType"/>
           <xs:attribute name="tzurl" type="TZURLType"/>
         </xs:extension>
       </xs:complexContent>
     </xs:complexType>
     <xs:element name="time-switch" type="TimeSwitchType"
         substitutionGroup="switch"/>
     <xs:simpleType name="PriorityValues">
       <xs:restriction base="xs:NMTOKEN">
         <xs:pattern
             value="[e|E][m|M][e|E][r|R][g|G][e|E][n|N][c|C][y|Y]"/>
         <xs:pattern value="[u|U][r|R][g|G][e|E][n|N][t|T]"/>
         <xs:pattern value="[n|N][o|O][r|R][m|M][a|A][l|L]"/>
         <xs:pattern
             value="[n|N][o|O][n|N]-[u|U][r|R][g|G][e|E][n|N][t|T]"/>
       </xs:restriction>
     </xs:simpleType>
     <xs:complexType name="PriorityType">
       <xs:annotation>
         <xs:documentation>Exactly one of the three attributes must
             appear </xs:documentation>

       </xs:annotation>
       <xs:group ref="Node"/>
       <xs:attribute name="less" type="PriorityValues"/>
       <xs:attribute name="greater" type="PriorityValues"/>
       <xs:attribute name="equal" type="xs:string">
         <xs:annotation>
           <xs:documentation>case-insensitive</xs:documentation>
         </xs:annotation>
       </xs:attribute>
       <xs:anyAttribute namespace="##any" processContents="lax"/>
     </xs:complexType>
     <xs:complexType name="PrioritySwitchType">
       <xs:complexContent>
         <xs:extension base="SwitchType">
           <xs:sequence>
             <xs:element name="priority" type="PriorityType"
                 minOccurs="0" maxOccurs="unbounded"/>
             <xs:sequence minOccurs="0">
               <xs:element name="not-present" type="NotPresentAction"/>
               <xs:element name="priority" type="PriorityType"
                   minOccurs="0" maxOccurs="unbounded"/>
             </xs:sequence>
             <xs:element name="otherwise" type="OtherwiseAction"
                 minOccurs="0"/>
           </xs:sequence>
         </xs:extension>
       </xs:complexContent>
     </xs:complexType>
     <xs:element name="priority-switch" type="PrioritySwitchType"
         substitutionGroup="switch"/>
     <xs:simpleType name="LocationPriorityType">
       <xs:restriction base="xs:float">
         <xs:minInclusive value="0.0"/>
         <xs:maxInclusive value="1.0"/>
       </xs:restriction>
     </xs:simpleType>
     <xs:complexType name="LocationType">
       <xs:complexContent>
         <xs:extension base="ModifierType">
           <xs:group ref="Node"/>
           <xs:attribute name="url" type="xs:anyURI" use="required"/>
           <xs:attribute name="priority" type="LocationPriorityType"
               use="optional" default="1.0"/>
           <xs:attribute name="clear" type="YesNoType" default="no"/>
         </xs:extension>
       </xs:complexContent>
     </xs:complexType>
     <xs:complexType name="LookupType">

       <xs:complexContent>
         <xs:extension base="ModifierType">
           <xs:all>
             <xs:element name="success" minOccurs="0">
               <xs:complexType>
                 <xs:group ref="Node"/>
               </xs:complexType>
             </xs:element>
             <xs:element name="notfound" minOccurs="0">
               <xs:complexType>
                 <xs:group ref="Node"/>
               </xs:complexType>
             </xs:element>
             <xs:element name="failure" minOccurs="0">
               <xs:complexType>
                 <xs:group ref="Node"/>
               </xs:complexType>
             </xs:element>
           </xs:all>
           <xs:attribute name="source" type="xs:string"
               use="required"/>
           <xs:attribute name="timeout" type="xs:positiveInteger"
               default="30"/>
           <xs:attribute name="clear" type="YesNoType" default="no"/>
         </xs:extension>
       </xs:complexContent>
     </xs:complexType>
     <xs:complexType name="RemoveLocationType">
       <xs:complexContent>
         <xs:extension base="ModifierType">
           <xs:group ref="Node"/>
           <xs:attribute name="location" type="xs:string"
               use="optional"/>
         </xs:extension>
       </xs:complexContent>
     </xs:complexType>
     <xs:complexType name="LogAction">
       <xs:complexContent>
         <xs:extension base="ActionType">
           <xs:group ref="Node"/>
           <xs:attribute name="name" type="xs:string" use="optional"/>
           <xs:attribute name="comment" type="xs:string"
               use="optional"/>
         </xs:extension>
       </xs:complexContent>
     </xs:complexType>
     <xs:element name="log" type="LogAction"
         substitutionGroup="action"/>

     <xs:complexType name="IncomingType">
       <xs:complexContent>
         <xs:extension base="TopLevelActionType"/>
       </xs:complexContent>
     </xs:complexType>
     <xs:element name="incoming" type="IncomingType"
         substitutionGroup="toplevelaction"/>
     <xs:complexType name="OutgoingType">
       <xs:complexContent>
         <xs:extension base="TopLevelActionType"/>
       </xs:complexContent>
     </xs:complexType>
     <xs:element name="outgoing" type="OutgoingType"
         substitutionGroup="toplevelaction"/>
     <xs:complexType name="ProxyAction">
       <xs:complexContent>
         <xs:extension base="ActionType">
           <xs:all>
             <xs:element name="busy" minOccurs="0">
               <xs:complexType>
                 <xs:group ref="Node"/>
               </xs:complexType>
             </xs:element>
             <xs:element name="noanswer" minOccurs="0">
               <xs:complexType>
                 <xs:group ref="Node"/>
               </xs:complexType>
             </xs:element>
             <xs:element name="failure" minOccurs="0">
               <xs:complexType>
                 <xs:group ref="Node"/>
               </xs:complexType>
             </xs:element>
             <xs:element name="redirection" minOccurs="0">
               <xs:complexType>
                 <xs:group ref="Node"/>
               </xs:complexType>
             </xs:element>
             <xs:element name="default" minOccurs="0">
               <xs:complexType>
                 <xs:group ref="Node"/>
               </xs:complexType>
             </xs:element>
           </xs:all>
           <xs:attribute name="timeout" type="xs:positiveInteger"
               use="optional" default="20"/>
           <xs:attribute name="recurse" type="YesNoType"
               use="optional" default="yes"/>

           <xs:attribute name="ordering" type="OrderingType"
               use="optional" default="parallel"/>
         </xs:extension>
       </xs:complexContent>
     </xs:complexType>
     <xs:element name="proxy" type="ProxyAction"
         substitutionGroup="action"/>
     <xs:complexType name="RedirectAction">
       <xs:complexContent>
         <xs:extension base="ActionType">
           <xs:attribute name="permanent" type="YesNoType"
               default="no"/>
         </xs:extension>
       </xs:complexContent>
     </xs:complexType>
     <xs:element name="redirect" type="RedirectAction"
         substitutionGroup="action"/>
     <xs:complexType name="RejectAction">
       <xs:complexContent>
         <xs:extension base="ActionType">
           <xs:attribute name="status" type="StatusType"
               use="required"/>
           <xs:attribute name="reason" type="xs:string"
               use="optional"/>
         </xs:extension>
       </xs:complexContent>
     </xs:complexType>
     <xs:element name="reject" type="RejectAction"
         substitutionGroup="action"/>
     <xs:complexType name="MailAction">
       <xs:complexContent>
         <xs:extension base="ActionType">
           <xs:group ref="Node"/>
           <xs:attribute name="url" type="xs:anyURI" use="required"/>
         </xs:extension>
       </xs:complexContent>
     </xs:complexType>
     <xs:element name="mail" type="MailAction"
         substitutionGroup="action"/>
     <xs:complexType name="SubAction">
       <xs:attribute name="ref" type="xs:string" use="required"/>
     </xs:complexType>
     <xs:complexType name="AncillaryType"/>
     <xs:complexType name="SubactionType">
       <xs:group ref="Node"/>
       <xs:attribute name="id" use="required"/>
     </xs:complexType>
     <xs:complexType name="CPLType">

       <xs:sequence>
         <xs:element name="ancillary" type="AncillaryType" minOccurs="0"
             maxOccurs="1"/>
         <xs:element name="subaction" type="SubactionType" minOccurs="0"
             maxOccurs="unbounded"/>
         <xs:element ref="toplevelaction" minOccurs="0"
             maxOccurs="unbounded">
           <xs:annotation>
             <xs:documentation>Any toplevel action MUST NOT appear more
                 than once.</xs:documentation>
           </xs:annotation>
         </xs:element>
       </xs:sequence>
     </xs:complexType>
     <xs:element name="cpl" type="CPLType"/>
   </xs:schema>
   END

Normative References

   [1]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
        Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP:
        Session Initiation Protocol", RFC 3261, June 2002.

   [2]  Bray, T., Paoli, J., Sperberg-McQueen, C. M., Maler, E., and F.
        Yergeau, "Extensible Markup Language (XML) 1.0 (Third Edition)",
        W3C Recommendation REC-xml-20040204, World Wide Web Consortium
        (W3C), February 2004.  Available at http://www.w3.org/XML/.

   [3]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
        Levels", BCP 14, RFC 2119, March 1997.

   [4]  Hinden, R. and S. Deering, "Internet Protocol Version 6 (IPv6)
        Addressing Architecture", RFC 3513, April 2003.

   [5]  Davis, M. F. and M. Duerst, "Unicode Normalization Forms",
        Unicode Standard Annex #15, Unicode Consortium, April 2003.
        Revision 23; part of Unicode 4.0.0. Available at
        http://www.unicode.org/unicode/reports/tr15/.

   [6]  Davis, M. F., "Case Mappings", Unicode Standard Annex #21,
        Unicode Consortium, March 2001.  Revision 5; part of Unicode
        3.2.0.  Available at
        http://www.unicode.org/unicode/reports/tr21/.

   [7]  Alvestrand, H., "Tags for the Identification of Languages", BCP
        47, RFC 3066, January 2001.

   [8]  Dawson, F. and D. Stenerson, "Internet Calendaring and
        Scheduling Core Object Specification (iCalendar)", RFC 2445,
        November 1998.

   [9]  Eggert, P., "Sources for Time Zone and Daylight Saving Time
        Data".  Available at http://www.twinsun.com/tz/tz-link.htm.

   [10] Mealling, M. and R. Daniel, "URI Resolution Services Necessary
        for URN Resolution", RFC 2483, January 1999.

   [11] Bray, T., Hollander, D., and A. Layman, "Namespaces in XML", W3C
        Recommendation REC-xml-names-19990114, World Wide Web Consortium
        (W3C), January 1999.  Available at http://www.w3.org/TR/REC-
        xml-names/.

   [12] Moats, R., "URN Syntax", RFC 2141, May 1997.

   [13] Moats, R., "A URN Namespace for IETF Documents", RFC 2648,
        August 1999.

   [14] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, January
        2004.

   [15] Murata, M., St.Laurent, S., and D. Kohn, "XML Media Types", RFC
        3023, January 2001.

Informative References

   [16] International Telecommunication Union, "Packet-based multimedia
        communication systems", Recommendation H.323, Telecommunication
        Standardization Sector of ITU, Geneva, Switzerland, July 2003.

   [17] Lennox, J. and H. Schulzrinne, "Call Processing Language
        Framework and Requirements", RFC 2824, May 2000.

   [18] Raggett, D., Le Hors, A., and I. Jacobs, "HTML 4.01
        Specification", W3C Recommendation REC-html401-19991224, World
        Wide Web Consortium (W3C), December 1999.  Available at
        http://www.w3.org/TR/html4/.

   [19] ISO (International Organization for Standardization),
        "Information processing -- Text and office systems -- Standard
        Generalized Markup Language (SGML)", ISO Standard ISO
        8879:1986(E), International Organization for Standardization,
        Geneva, Switzerland, October 1986.

   [20] ISO (International Organization for Standardization), "Data
        elements and interchange formats -- Information interchange --
        Representation of dates and times", ISO Standard ISO
        8601:2000(E), International Organization for Standardization,
        Geneva, Switzerland, December 2000.

   [21] DeRose, S., Maler, E., Orchard, D., and B. Trafford, "XML
        Linking Language (XLink) Version 1.0", W3C Recommendation REC-
        xlink-20010627, World Wide Web Consortium (W3C), June 2001.
        Available at http://www.w3.org/TR/xlink/.

   [22] Showalter, T., "Sieve: A Mail Filtering Language", RFC 3028,
        January 2001.

   [23] International Telecommunication Union, "Digital Subscriber
        Signalling System No. 1 (DSS 1) - ISDN user-network interface
        layer 3 specification for basic call control", Recommendation
        Q.931, International Telecommunication Union, Geneva,
        Switzerland, March 1993.

   [24] Levin, O., "H.323 Uniform Resource Locator (URL) Scheme
        Registration", RFC 3508, April 2003.

Authors' Addresses

   Jonathan Lennox
   Dept. of Computer Science
   Columbia University
   1214 Amsterdam Avenue, MC 0401
   New York, NY 10027
   USA

   EMail: lennox@cs.columbia.edu


   Xiaotao Wu
   Dept. of Computer Science
   Columbia University
   1214 Amsterdam Avenue, MC 0401
   New York, NY 10027
   USA

   EMail: xiaotaow@cs.columbia.edu


   Henning Schulzrinne
   Dept. of Computer Science
   Columbia University
   1214 Amsterdam Avenue, MC 0401
   New York, NY 10027
   USA

   EMail: schulzrinne@cs.columbia.edu

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