Sba`_^]\[ZYXWVUTSRQPONMLKJIHGFEDCBA@?>=<;:9876543210/.-,+*)('&%$#"!  2  `^BLTT TTTJM*This section covers the following topics:*  a)Naming $ b)Addressing!  c)Routing  J  17.Naming b NThis clause specifies how users and DLs are nameOF 2another MD for the purpose, e.g., of conversion. 2aJMMg)An MD may route to a malformed O/R address provided (of course) that it MH4contains at least the attributes required to do so.4d PNote The bilateral agreements and local rules alluded to above are beyond the Pd Pscope of this Recommendation and may be based upon technical, policy, economic, P-J or other considerations.s a MD to which no direct connection exists, routing may be M_ Kbased upon .I.ba:routing;bilateral agreements with the MDs to which direct K@ ,connections do exist and other local rules.,d Pe)When the MD is directly connected to the MD identified by the O/R address, PH 4the object is typically routed to that MD directly.4_ Kf)By .I.ba:routing;bilateral agreement, one MD might route an object to Ke connected to a single, ADMD. When this is so, routing always P3 involves the ADMD necessarily.d Pc)An ADMD may be connected to multiple PRMDs. When this is so, routing may beP` Lbased upon conditional O/R address attributes, including but not limited to L) private-domain-name.d Pd)An MD may be directly connected to some but not all other MDs. When the O/RPaDJMaddress identifieo that location.*^ JExternal routing is an incremental and only loosely standardized process. Jd PSuggested below are several principles of external routing. Internal routing is P> *outside the scope of this Recommendation.*O ;The following principles are illustrative, not definitive:;c Oa)In an MHS that comprises a single MD, of course, routing is not an issue.Od Pb)A PRMD may bfic to postal O/R addresses are present orPd Pabsent in such O/R addresses so as to satisfy the postal addressing requirementsP0 of the users they identify. !J  19.Routing d Ppo convey a message, probe, or report toward a user or the expansion point of a Pb NDL, an MTA must not only locate the user or DL (i.e., obtain its O/R address) N> *but also select a route ts on the attributes in the O/R address. If a user is not Ia Maccessed through a PRMD, all conditional attributes except those specific to Md Ppostal O/R addresses are present in an O/R address at the discretion of, and in Pc Oaccordance with rules established by, the ADMD denoted by the country-name and O; 'administration-domain-name attributes.' d P^^^^^^All conditional attributes specin Table 10/X.402 is determined as follows.? _ K If a user or DL is accessed through a PRMD, attributes used to route Kd Pmessages to the PRMD are present in the O/R address at the discretion of, and inPb Naccordance with rules established by the ADMD denoted by the country-name and NbDJNadministration-domain-name attributes of the O/R address. The ADMD imposes no N] Iother constraint provide information additional to that O/ which identifies the user.d PThe private-domain-name and the domain-defined attributes shall be present only P_ Kif the country-name and administration-domain-name attributes are present.K0 18.6Conditional Attributes ` L^^^^^^The presence or absence in a particular O/R address of the attributes LS ?marked conditional iributes:;. a)One network-address.A -b)Conditionally, one terminal-identifier.-;J 'c)Conditionally, one terminal-type.'aMd)Conditionally, both one country-name and one administration-domain-name M5 !which together identify an ADMD.!` Le)Conditionally, one private-domain-name and, conditionally, one or more Lc Odomain-defined attributes, all of whichd Pnetwork address and, if required, the type of his terminal. It may also identifyPaDJMthe ADMD through which that terminal is accessed. In the case of a Telematic M` Lterminal, it gives the terminal's network address and possibly its terminal L` Lidentifier and terminal type. In the case of a Telex terminal, it gives its L"JMTelex number.O ;A terminal O/R address comprises the following atthould be small enough to permit their rendition in 6 linesPd Pof 30 characters, the size of a typical physical envelope window. The rendition Pd Palgorithm is PDAU-specific but is likely to include inserting delimiters (e.g., P< (spaces) between some attribute values.( 3 18.5.4Terminal O/R Address` LA .I.gl:terminal O/R address; is one that identifies a user by means of the L 5that the PDS requires to identify the postal patron.5 Y E^^^^^^An unformatted postal O/R address comprises, additionally, one E: &unformatted-postal-address attribute.& ` JNote - The total number of characters in the values of all attributes but Fd Pcountry-name, administration-domain-name, and physical-delivery-service-name in Pd Pa postal O/R address s a Mc) One physical-delivery-country-name and one postal-code, which together M_ K^^^^^^identify the geographical region in which the user takes delivery of K- ^^^^^^physical messages. ^^^^^^d P^^^^^^A formatted postal O/R address comprises, additionally, one of each postalPa Maddressing attribute (see Table 9/X.402), except unformatted-postal-address, MIstal O/R address, whether formatted or unformatted, comprises the following P  attributes: ] Ia)One country-name and one administration-domain-name, which together I& identify an ADMD.`J Lb)^^^^Conditionally, one private-domain-name, one physical-delivery-service-Lc O^^^^^^name, or both which together identify the PDS by means of which the user O- ^^^^^^is to be accessed.ttributes. For this form of postal O/R Ka Maddress, this Recommendation prescribes the structure of postal addresses in M!  some detail. b Nb).I.gl:unformatted;: Said of a postal O/R address that specifies a user's Nd Ppostal address in a single attribute. For this form of postal O/R address, this PaDJMRecommendation largely does not prescribe the structure of postal addresses.MdJMPA podressd PA .I.gl:postal O/R address; is one that identifies a user by means of its postalP` Laddress. It identifies the PDS through which the user is to be accessed and L5 !gives the user's postal address.!Q =The following kinds of postal O/R address are distinguished:=` La).I.gl:formatted;: Said of a postal O/R address that specifies a user's L_ Kpostal address by means of several a one administration-domain-name, which together I&identify an ADMD.b Nb)One numeric-user-identifier and, conditionally, one private-domain-name, N[ Gwhich together identify the user relative to the ADMD in item a above.G\ Hc)Conditionally, one or more domain-defined attributes which provide HN :information additional to that which identifies the user.:1 18.5.3Postal O/R Adve; and optionally one or more domain-defined attributes; which together PP <identify a user or DL relative to the ADMD in item a above.<2J 18.5.2Numeric O/R Address_ KA .I.gl:numeric O/R address; is one that numerically identifies a user. It KC /identifies an ADMD, and a user relative to it./N :A numeric O/R address comprises the following attributes::] Ia)One country-name andL 8It identifies an ADMD, and a user or DL relative to it.8O ;A mnemonic O/R address comprises the following attributes:;] Ia)One country-name and one administration-domain-name, which together I& identify an ADMD.MJM9b)One private-domain-name, one organization-name, one 9dDJPorganizational-unit-names, one personal-name or common-name, or a combination ofPd Pthe aboT postal Pb N C conditional | | TERM terminal | ND 0+---------------------------------------------+0d PThe forms of O/R address, summarized in the table, are individually defined and P4  described in the clauses below. 3 18.5.1Mnemonic O/R Addressd PA .I.gl:mnemonic O/R address; is one that mnemonically identifies a user or DL. PP; ' - C - - | +- Domain-defined 'dP--------------------+-------------------------+ | domain-defined (one or more) P6 " | C C - - C | "a M+-------------------------------------+-------------------------+ +- Legend M\ H------------------------------------+ | MNEM mnemonic F formatted M Hd Pmandatory | | NUMR numeric U unformatted O optional | | POS C - - | | BV Bphysical-delivery-personal-name | - - C - - | | BV Bpost-office-box-address | - - C - - | | Bd Pposte-restante-address | - - C - - | | street-addressPd P | - - C - - | | unformatted-postal-address Pd P | - - - M - | | unique-postal-name | - - - | | extension-physical-delivery | - - PdJMP C - - | | -address-components | P[ G | | local-postal-attributes | - - C - - | | GV Bphysical-delivery-office-name | - - C - - | | BVDJBphysical-delivery-office-number | - - C - - | | BVJ Bphysical-delivery-organization-name | - - C | +- Postal Routing --------------------+-------------------------+ | LV BPDS-name | - - O O - | | Bd Pphysical-delivery-country-name | - - M M - | | postal-code P[ G | - - M M - | +- Postal Addressing Gd P-----------------+-------------------------+ | extension-O/R-address-components Pd P | - - C - | | organization-name | C - C - - | | Ld Porganizational-unit-names | C - - - - | | personal-name Pd P | C - C - - | | private-domain-name Pd P | C C C C C | | terminal-identifier | - Pd P - - - C | | terminal-type | - - - - P` L +- General ---------------------------+-------------------------+ | Nd Padministration-domain-name | M M M M C | | common-name Pd P | C - C - - | | country-name PdP | M M M M C | | network-address | - Pd P - - - M | | numeric-user-identifier | - M - - P` L <DJ(Table .T.:10/X.402 Forms of O/R Address(d P+-------------------------------------+-------------------------+ | Pd P | O/R Address Forms | | Pd P +-------------------------+ | | Pd P POST | | Attribute Type | MNEM NUMR F Pb NU TERM |/R address form, the second column indicates the J`JMLattributes that may appear in such O/R addresses and their grades (see also L" clause 18.6).cO^^^^^^The table has four sections. Attribute types in the first are those of a O^ Jgeneral nature, attribute types in the second and third those specific to Ja Mphysical delivery. The fourth section encompasses domain-defined attributes.MDL is assigned one or more O/R addresses. An .I.gl:O/R address; isPb Nan attribute list that distinguishes one user from another and identifies the NS ?user's point of access to the MHS or the DL's expansion point.?d PAn O/R address may take any of the forms summarized in Table 10/X.402. The firstPd Pcolumn of the table identifies the attributes available for the construction of P^ JO/R addresses. For each Oracters in attribute values, the case of letters in such values, or the KA-relative order of domain-defined attributes.-c O2. As a national matter, MDs may impose additional equivalence rules regarding Ob Nstandard attributes whose values are given as Teletex Strings, in particular, NM 9the rules for deriving the equivalent Printable Strings.9+ 18.5O/R Address Formsd PEvery user or Me)In a domain-defined attribute type or value, or in a standard attribute Mb Nvalue, all leading, all trailing, and all but one consecutive embedded spaces N7 #shall be considered insignificant.# Notesd P1. An MD may impose additional equivalence rules upon the attributes it assigns Pb Nto its own users and DLs. It might define, e.g., rules concerning punctuation N_ Kchahem shall be considered I# insignificant._ Kc)Where the value of a standard attribute may be a Printable String, an KcJ Oequivalent Teletex String, or both, the choice between the three possibilities O7 #shall be considered insignificant.#c Od)Where the value of a standard attribute may contain letters, the cases of ODDJ0those letter shall be considered insignificant.0a O/R addresses, and thus several attribute lists, may denote the same Md Puser or DL. This multiplicity of O/R addresses results in part (but not in full)PI 5from the following attribute list equivalence rules:5U Aa)The relative order of standard attributes is insignificant.A_JMKb)Where the value of a standard attribute may be a Numeric String or an K] Iequivalent Printable String, the choice between tme; is a standard attribute that identifies the point ofPd Pdelivery, other than that denoted by a street-address, post-office-box-address, PaMor poste-restante-address, (e.g., a building or hamlet) of a user's physical M  messages. ` LThe value of a unique-postal-name is a Printable String, Teletex String, or L both.4  18.4Attribute List Equivalence a MSeveralAn .I.gl:unformatted-postal-address; is a standard attribute that specifies a N8 $user's postal address in free form.$c OThe value of an unformatted-postal-address is a sequence of Printable Strings, Od Peach representing a line of text; a single Teletex String, lines being separatedP= )as prescribed for such strings; or both.)1 18.3.26Unique-postal-named PA .I.gl:unique-postal-na :The value of a terminal-identifier is a Printable String.:, 18.3.24Terminal-type\J HA .I.gl:terminal-type; is a standard attribute that gives the type of a H  terminal. a MThe value of a terminal-type is any one of the following: Telex, Teletex, G3 MI 5facsimile, G4 facsimile, IA5 terminal, and Videotex.59 %18.3.25Unformatted-postal-address%bDJNumber and street name and type (e.g., "Road")) at which a P> *user takes delivery of physical messages.*T @The value of a street-address is a Printable or Teletex String.@2 18.3.23Terminal-identifiera MA .I.gl:terminal-identifier; is a standard attribute that gives the terminal M^JMJidentifier of a terminal (e.g., a Telex answer back or a Teletex terminal J!  identifier). Nthat is administered for this purpose by the O+ ADMD alluded to above. ^ HNote - In countries choosing country-wide unique PRMD names, a national DQ =registration authority for private-domain-names is required.= -18.3.22Street-address^ JA .I.gl:street-address; is a standard attribute that specifies the street Jd Paddress (e.g., house n attribute that identifies a PRMD. AsPa Ma national matter, this identification may be either relative to the country Md Pdenoted by a country-name (so that PRMD names are unique within the country), orPVBrelative to the ADMD identified by an administration-domain-name.B` L^^^^^^^^The value of a private-domain-name is a Numeric or Printable String Lc Ochosen from a set of such strings ct the physical messages M0 that await delivery to him.d PThe value of a poste-restante-address is a Printable String, Teletex String, or PcDJOboth chosen from the set of such strings assigned for this purpose by the post OQ =office denoted by a physical-delivery-office-name attribute.=2 18.3.21Private-domain-name d P^^^^^^^^A private-domain-name is a standardable String chosen from the set P` Lof such strings that is maintained and standardized for this purpose by the LIJ 5postal administration of the country identified by a 5> *physical-delivery-country-name attribute.*5 !18.3.20Poste-restante-address!d PA .I.gl:poste-restante-address; is a standard attribute that specifies the code Pa Mthat a user gives to a post office in order to colle orPc Oboth chosen from the set of such strings assigned for this purpose by the post OQ =office denoted by a physical-delivery-office-name attribute.=* 18.3.19Postal-codedJMPA .I.gl:postal-code; is a standard attribute that specifies the postal code for P_ Kthe geographical area in which a user takes delivery of physical messages.Kd PThe value of a postal-code is a Numeric or Printlue of a physical-delivery-personal-name is a Printable String, Teletex N% String, or both.6 "18.3.18Post-office-box-address"` LA .I.gl:post-office-box-address; is a standard attribute that specifies the L] Inumber of the post office box by means of which a user takes delivery of I'physical messages.d PThe value of a post-office-box-address is a Printable String, Teletex String,delivery-organization-name; is a standard attribute that J? +identifies a postal patron's organization.+^ JThe value of a physical-delivery-organization-name is a Printable String, J- Teletex String, or both.>DJ*18.3.17Physical-delivery-personal-name*d PA .I.gl:physical-delivery-personal-name; is a standard attribute that identifiesP% a postal patron.b NThe va-delivery-office-number*Z FA .I.gl:physical-delivery-office-number; is a standard attribute that FQJ =distinguishes among several post offices denoted by a single =3 physical-delivery-office-name.b NThe value of a physical-delivery-office-number is a Printable String, Teletex N% String, or both.B .18.3.16Physical-delivery-organization-name.^ JA .I.gl:physical-< (18.3.14Physical-delivery-office-name(cOA .I.gl:physical-delivery-office-name; is a standard attribute that identifies Oa Mthe city, village, etc. in which is situated the post office through which a M> *user takes delivery of physical messages.*`JMLThe value of a physical-delivery-office-name is a Printable String, Teletex L% String, or both.> *18.3.15Physicaln is supplied as Printable Strings, Teletex Strings, or L both.= )18.3.13Physical-delivery-country-name)d PA .I.gl:physical-delivery-country-name; is a standard attribute that identifies PU Athe country in which a user takes delivery of physical messages.Ad PThe value of a physical-delivery-country-name is subject to the same constraintsP7 #as is the value of a country-name.#ted by another attribute (e.g., an organization-name).Id PThe value of a personal-name comprises the following four pieces of information,P> *the first mandatory, the others optional:*/ a)The person's surname.2 b)The person's given name.K 7c)The initials of all of his names but his surname.77 #d)His generation (e.g., "Jr.").#`DJLThe above informatiotifies a PDS NS ?relative to the ADMD denoted by an administration-domain-name.?dJ PThe value of a PDS-name is a Printable String chosen from a set of such strings PX Dthat is administered for this purpose by the ADMD alluded to above.D , 18.3.12Personal-named PA .I.gl:personal-name; is a standard attribute that identifies a person relativeP] Ito the entity deno OStrings, an ordered sequence of Teletex Strings, or both. Whether Printable or Oc OTeletex, each string is chosen from a set of such strings that is administered OdPfor this purpose (and perhaps others) by the organization (or encompassing unit)P&JMalluded to above.= )18.3.11Physical-delivery service-name) b N^^^^^^^A Physical-delivery-name is a standard attribute that idenganizational-unit-names$d PAn .I.gl:organizational-unit-names; is a standard attribute that identifies one Pd Por more units (e.g., divisions or departments) of the organization denoted by anPc Oorganization-name, each unit but the first being a sub-unit of the units whose O7 #names precede it in the attribute.#b NThe value of an organizational-unit-names is an ordered sequence of Printable Nc Oor both. Whether Printable or Teletex, the string is chosen from a set of such O^ Jstrings that is administered for this purpose (and perhaps others) by the J. country alluded to above. f PNote - In countries choosing country-wide unique organization-names, a national LO ;registration authority for organization-names is required.; 8DJ$18.3.10OrGc Oorganization. As a national matter, this identification may be either relative Od Pto the country denoted by a country-name (so that organization names are unique Pd Pwithin the country), or relative to the MD identified by a private-domain-name, P? +or an administration-domain-name, or both.+ d P^^^^^^^The value of an organization-name is a Printable String, Teletex String, Pc Jsuch strings that is administered for this purpose by the ADMD alluded to J above. f PNote - In countries choosing country-wide unique organization-names, a national LO ;registration authority for organization-names is required.; 0 18.3.9Organization-name [ G^^^^^^^An organization-name is a standard attribute that identifies an ecommendation X.121 is a Telex number H< (preceded by the Telex escape digit (8).(6 "18.3.8Numeric-user-identifier"^J JA .I.gl:numeric-user-identifier; is a standard attribute that numerically JI 5identifies a user relative to the ADMD denoted by an 50 administration-domain-name.d PThe value of a numeric-user-identifier is a Numeric String chosen from a set of P^ sdDJPA .I.gl:network-address; is a standard attribute that gives the network address P# of a terminal.P <The value of a network-address is any one of the following:<L 8a)A Numeric String governed by Recommendation X.121.8Z Fb)Two Numeric Strings governed by Recommendations E.163 and E.164.F+JMc) A PSAP address.bLNote - Among the strings admitted by Rbutes"a MA .I.gl:local-postal-attributes; is a standard attribute that identifies the MH 4locus of distribution, other than that denoted by a 4d Pphysical-delivery-office-name attribute (e.g., a geographical area), of a user'sP' physical messages.d PThe value of a local-postal-attributes is a Printable String, Teletex String, orP both.. 18.3.7Network-addresnsion-physical-delivery-address-components; is a standard attributeP] Ithat specifies, in a postal address, additional information necessary to Ib Nidentify the exact point of delivery (e.g., room and floor numbers in a large N  building). b NThe value of an extension-physical-delivery-address-components is a Printable N5 !String, Teletex String, or both.!6 "18.3.6Local-postal-attri^^^^^^An extension-postal-O/R-address-components; is a standard attribute that Pd Pprovides, in a postal address, additional information necessary to identify the P>JM*addressee (e.g., an organizational unit).*d PThe value of an extension-O/R-address-components is a Printable String, Teletex P%String, or both.MJ 918.3.5Extension-physical-delivery-address-components9d PAn .I.gl:exte+ 18.3.3Country-name] IA .I.gl:country-name; is a standard attribute that identifies a country.IcDJOThe value of a country-name is a Numeric String that gives the number assigned Oa Mto the country by Recommendation X.121, or a Printable String that gives the MH 4character pair assigned to the country by ISO 3166.4? +18.3.4Extension-O/R-address-components+d P^_ KThe value of a common-name is a Printable String, Teletex String, or both. Kb NWhether Printable or Teletex, the string is chosen from a set of such strings Nd Pthat is administered for this purpose (and perhaps others) by the entity alludedP  to above. [ GNote Among many other possibilities, a common-name might identify an GI 5organizational role (e.g., "Director of Marketing").5rejects the note and ISO elects to Pb Ninclude it in its corresponding International Standard, as is likely, a major N^ Jdifference between the CCITT Recommendation and ISO Standard will result.J* 18.3.2Common-name^ JA .I.gl:common-name; is a standard attribute that identifies a user or DL JR >relative to the entity denoted by another attribute (e.g., an >( organization-name).n the country indiscriminantly, andPd Prequires that the ADMDs within the country interconnect themselves in such a wayP_ Kthat the messages, probes, and reports are conveyed to their destinations.KbJ NTemporary note The inclusion of the above note is tentative, subject to the NcOapproval of Administrations. The note would resolve a long-standing difference Od Pbetween CCITT and ISO in this area. If CCITT eports to and among the ADMDs of that L_DJKcountry. Regarding the former, it requires that the O/R addresses of users Kd Pwithin the country be chosen so as to ensure their unambiguousness, even in the P^ Jabsence of the actual names of the users' ADMDs. Regarding the latter, it JdJMPpermits both PRMDs within, and ADMDs outside of the country, to route messages, Pd Pprobes, and reports to any of the ADMDs withi country alluded to above.d PNote The attribute value comprising a single space (" ") shall be reserved forPc Othe following purpose. If permitted by the country denoted by the country-name O_ Kattribute, a single space shall designate any (i.e., all) ADMDs within the Kb Ncountry. This affects both the identification of users within the country and N` Lthe routing of messages, probes, and r8 $and described in the clauses below.$9 %18.3.1Administration-domain-name%d PAn .I.gl:administration-domain-name; is a standard attribute that identifies an PL 8ADMD relative to the country denoted by a country-name.8` LThe value of an administration-domain-name is a Numeric or Printable String Lc Ochosen from a set of such strings that is administered for this purpose by the O.Bc O+------------------------------------------------+----------------+ +- Legend OdP------------------------------------+ | NUM numeric x permitted Pd P | | PRT printable * Under prescribed circum- | | TTX teletex stancesPY Ea Printable String | +---------------------------------------------+Ed PThe standard attribute types, summarized in the table, are individually defined Pery-personal-name | - x x | | DX Dpost-office-box-address | - x x | | DX Dposte-restante-address | - x x | | DX Dstreet-address | - x x | | DXJ Dunformatted-postal-address | - x x | | DV Bunique-postal-name | - x x | x x | | DX Dextension-physical-delivery-address-components | - x x | | DX Dlocal-postal-attributes | - x x | | DX Dphysical-delivery-office-name | - x x | | DX Dphysical-delivery-office-number | - x x | | DXDJDphysical-delivery-organization-name | - x x | | DXJMDphysical-deliv PRouting -------------------------------+----------------+ | PDS-name Pd P | - x - | | physical-delivery-country-name Pd P | x x - | | postal-code P? + | x x - | +- Postal Addressing +E 1----------------------------+----------------+ | 1X Dextension-O/R-address-components | - | - x xP^ J | | organizational-unit-names | - x x | | JX Dpersonal-name | - x x | | DX Dprivate-domain-name | x x - | | DX Dterminal-identifier | - x - | | D` Lterminal-type | - - - | +- Postal Ld --------+ | ;d Padministration-domain-name | x x - | | common-name Pd P | - x x | | country-name Pd P | x x - | | network-address Pd P | x(*) - - | | numeric-user-identifier |PdP x - - | | organization-name /: &Table .T.:9/X.402 Standard Attributes&dJMP+------------------------------------------------+----------------+ | PdDJP | Character Sets | | Pd P +----------------+ | Standard Attribute Type P? + | NUM PRT TTX | +- General +OJ ;--------------------------------------+--------listed in the first column of Table 9/X.402. Nc OFor each listed type, the second column indicates the character sets--numeric, OV Bprintable, and teletex--from which attribute values may be drawn.B` LThe table has three sections. Attribute types in the first are of a general Lc Onature, those in the second have to do with routing to a PDS, and those in the OC /third have to do with addressing within a PDS.ttribute values to allow inclusion, e.g., OP <of the accented characters commonly used in many countries.<d P2. Not all input/output devices permit the entry and display, e.g., of accented Pc Ocharacters. Printable Strings are required internationally to ensure that such OE 1device limitations do not prevent communication.1- 18.3Standard Attributesb NThe standard attribute types are P convey the same information so that eiher of them can be safely ignored P(  upon receipt. d PThe length of each string and of each sequence of strings in an attribute shall P` Lbe limited as indicated in the more detailed (i.e., ASN.1) specification of L8$attributes in Recommendation X.411.$ Notesc O1. Teletex Strings are permitted in aKP <either variety (but not both) may be supplied equivalently.<d Pb) Wherever both Printable and Teletex Strings are permitted, strings of Pd P either or both varieties may be supplied, but Printable Strings shall be Pd P supplied as a minimum whenever attributes are conveyed internationally. Pd P If both Printable and Teletex Strings are supplied, the two should Pdone attribute to another (see clause 18.3).1`JMLThe value of an attribute comprises strings of one of the following sets of La Mvarieties depending upon its type: Numeric only, Printable only, Numeric and Md PPrintable, and Printable and Teletex. With respect to this, the following rules P;DJ'govern each instance of communication:'_J Ka)Wherever both Numeric and Printable Strings are permitted, strings of le, and Teletex Strings as follows:E] Ia)The type or value of a particular domain-defined attribute may be a Ic OPrintable String, a Teletex String, or both. The same choice shall be made for O- both the type and value.Z Fb)The kinds of strings from which standard attribute values may be Fd Pconstructed and the manner of construction (e.g., as one string or several) varyPE 1from s to permit an MD to retain its existing, native Ld Paddressing conventions for a time. It is intended, however, that all MDs migratePa Mtoward the use of standard attributes, and that domain-defined attributes be M5 !used only for an interim period.!( 18.2Character Sets` LStandard attribute values and domain-defined attribute types and values are LY Econstructed from Numeric, Printabion by an MD.b NBoth the type and value of every domain-defined attribute are strings or N, collections of strings.d PNote The widespread use of standard attributes produces more uniform and thus Pb Nmore user-friendly O/R addresses. However, it is anticipated that not all MDs NW Cwill be able to employ such attributes immediately. The purpose of C`Ldomain-defined attributes i +Attributes are of the following two kinds:+c Oa).I.gl:standard attribute;: An attribute whose type is bound to a class of O8 $information by this Recommendation.$`J LThe value of every standard attribute except terminal-type is either a L7DJ#string or a collection of strings.#` Lb).I.gl:domain-defined attribute;: An attribute whose type is bound to a L3 class of informatof N< (the MHS (or the network underlying it).(: &An attribute has the following parts:&d Pa).I.gl:attribute type; (or .I.gl:type;): An identifier that denotes a class P; 'of information (e.g., personal names).'_ Kb).I.gl:attribute value; (or .I.gl:value;): An instance of the class of K_JMKinformation the attribute type denotes (e.g., a particular personal name).K? N]Ithe data structures by means of which all such location is accomplished.I) 18.1Attribute Listsd PThe O/R addresses of both users and DLs are attribute lists. An .I.gl:attribute P; 'list; is an ordered set of attributes.'d PAn .I.gl:attribute; is an information item that describes a user or DL and that Pb Nmay also locate it in relation to the physical or organizational structure ttribute lists are equivalent and for the P` Linclusion of conditional attributes in such lists, and defines the standard L8 $attributes that may appear in them.$d PTo convey a message, probe, or report to a user, or to expand a DL specified as Pd Pa potential recipient of a message or probe, the MTS must locate the user or DL Pb Nrelative to its own physical and organizational structures. O/R addresses are r MS at PZJ Fdelivery, O/R names the UA or MS did not supply at direct submission.F$ 18.Addressingd PThis clause specifies how users and DLs are addressed. It defines O/R addresses,PdDJPdescribes the structure of the attribute lists from which they are constructed, P` Ldiscusses the character sets from which individual attributes are composed, Ld Pgives rules for determining that two aP At delivery the MTS includes an O/R address and possibly a Directory name Pd Pin each O/R name it supplies to a message's recipient or to the originator of a P] Ireport's subject message or probe. The Directory name is included if the Ic Ooriginator supplied it or if it was specified as the the member of an expanded O DL.d PNote Redirection or DL expansion may cause the MTS to convey to a UA ohe O/R Kb Naddress is omitted, the MTS obtains it from the Directory using the Directory Na Mname. If the Directory name is omitted, the MTS does without it. If both are Md Pincluded, the MTS relies firstly upon the O/R address. Should it determine that Pc Othe O/R address is invalid (e.g., obsolete), it proceeds as if the O/R address OG 3had been omitted, relying upon the Directory name.3d ame, an O/R address, or both. If Kc Opresent, the directory name (if valid) unambiguously identifies the user or DL Oa M(but is not necessarily the only name that would do so). If present, the O/R ML 8address does the same and more (again see clause 18.5).8c OAt direct submission, the UA or MS of the originator of a message or probe may O_ Kinclude either or both components in each O/R name it supplies. If tdDJPEvery user or DL has one or more O/R names. An .I.gl:O/R name; is an identifier Pb Nby means of which a user can be designated as the originator, or a user or DL N[ Gdesignated as a potential recipient of a message or probe. An O/R name Ga Mdistinguishes one user or DL from another and may also identify its point of M' access to the MHS._ TK^^^^^^^An O/R name comprises a Directory nly couched in terms of the Na Morganizational or physical structure of the MHS while the former need not be.MaJ MTherefore, it is intended that over time, Directory names become the primary M` Lmeans by which users and DLs are identified outside the MTS (i.e., by other Ld Pusers), and that the use of O/R addresses be largely confined to the MTS (i.e., P% to use by MTAs).# 17.2O/R Namesmmunication systems.Y E2. Users and DLs may be assigned Directory names even before a fully Ed Pinterconnected, distributed Directory has been put in place by pre-establishing P\ Hthe naming authorities upon which the Directory will eventually depend.H a M3. The typical Directory name is more user-friendly and more stable than the Mb Ntypical O/R address because the latter is necessariNNot every user or DL is registered in the Directory and, therefore, not every N; 'user or DL possesses a Directory name.'Notesb N1. Many users and DLs will lack Directory names until the Directory is widely Nc Oavailable as an adjunct to the MHS. Many indirect users (e.g., postal patrons) Ob Nwill lack such names until the Directory is widely available as an adjunct to N1 other coy NDDJ0means of which such identification is achieved.0) 17.1Directory Namesd PA Directory name is one component of an O/R name. A Directory name identifies anPd Pobject to the Directory. By presenting such a name to the Directory, the MHS canPa Maccess a user's or DL's Directory entry. From that entry the MTS can obtain, M: &e.g., the user's or DL's O/R address.&b for the purposes of Message Nd PHandling in general and Message Transfer in particular. It defines O/R names andPJ 6describes the role that Directory names play in them.6d PWhen it directly submits a message or probe, a UA or MS identifies its potentialP^ Jrecipients to the MTS. When the MTS delivers a message, it identifies the Jb Noriginator to each recipient's UA or MS. O/R names are the data structures bs " 16.Overview^ JThis section describes the naming and addressing of users and DLs and the J< (routing of information objects to them.(>JM*This section covers the following topics:*  a)Naming $ b)Addressing!  c)Routing  J  17.Naming b NThis clause specifies how users and DLs are named