Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools


Network Working Group P. Barker Request for Comments: 1617 University College London RARE Technical Report: 11 S. Kille Obsoletes: 1384 ISODE Consortium Category: Informational T. Lenggenhager

                                                              May 1994
    Naming and Structuring Guidelines for X.500 Directory Pilots

Status of this Memo

 This memo provides information for the Internet community.  This memo
 does not specify an Internet standard of any kind.  Distribution of
 this memo is unlimited.


 Deployment of a Directory will benefit from following certain
 guidelines. This document defines a number of naming and structuring
 guidelines focused on White Pages usage. Alignment to these
 guidelines is recommended for directory pilots. The final version of
 this document will replace RFC 1384.

Table of Contents

  1. Introduction                                                2
  2. DIT Structure                                               3
  2.1. Structure Rules                                           3
  2.2. The Top Level of the DIT                                  3
  2.3. Countries                                                 4
  2.4. Organisations                                             5
  2.4.1. Directory Manager, Postmaster & Secretary               5
  2.4.2. Depth of tree                                           6
  2.4.3. Real World Organisational Structure                     7
  2.5. Multi-National Organisations                              7
  2.5.1. The Multi-National as a Single Entity                   7
  2.5.2. The Multi-National as a Loose Confederation             8
  2.5.3. Loosely Linked DIT Sub-Trees                            9
  2.5.4. Summary of Advantages and Disadvantages of the
         Above Approaches                                        9
  3. Naming Style                                               10
  3.1. Multi-Component Relative Distinguished Names             11
  3.2. National Guidelines for Naming                           11
  3.3. Naming Organisation and Organisational Unit Names        11
  3.4. Naming Human Users                                       12
  3.5. Application Entities                                     13

RARE Working Group on Network Applications Support (WG-NAP) [Page 1] RFC 1617 Naming and Structuring Guidelines for X.500 May 1994

  4. Attribute Values                                           13
  4.1. Basic Attribute Syntaxes                                 13
  4.1.1. Printable String                                       14
  4.1.2. IA5 String - T.50                                      14
  4.1.3. Teletex String - T.61                                  14
  4.1.4. Case Ignore String                                     14
  4.1.5. Distinguished Name                                     14
  4.2. Languages & Transliteration                              14
  4.2.1. Languages other than English                           15
  4.2.2. Transliteration                                        15
  4.3. Access control                                           15
  4.4. Selected Attributes                                      16
  4.4.1. Personal Attributes                                    16
  4.4.2. Organisational Attributes                              18
  4.4.3. Local Attributes                                       19
  4.4.4. Miscellaneous Attributes                               20
  4.4.5. MHS Attributes                                         21
  4.4.6. Postal Attributes                                      21
  4.4.7. Telecom Attributes                                     22
  5. Miscellany                                                 22
  5.1. Schema consistency of aliases                            22
  5.2. Organisational Units                                     23
  6. References                                                 23
  7. Security Considerations                                    23
  8. Authors' Addresses                                         24
  9. Appendix - Example Entries                                 25

1. Introduction

 The intended audience for this document are mainly data managers
 using X.500 Directory Services. With the help of these guidelines it
 should be easier for them to define the structure for the part of the
 Directory Information Tree they want to model, e.g., the
 representation of their organisation in the Directory. In addition,
 decisions like which data elements to store for each kind of entry
 shall be supported.
 These guidelines concentrate mainly on the White Pages use of the
 Directory, the X.500 application with most operational experience
 today, nonetheless many recommendations are also valid for other
 applications of the Directory.
 As a pre-requisite to this document, it is assumed that the COSINE
 and Internet X.500 Schema is followed [1].

RARE Working Group on Network Applications Support (WG-NAP) [Page 2] RFC 1617 Naming and Structuring Guidelines for X.500 May 1994

2. DIT Structure

 The majority of this document is concerned with DIT structure, naming
 and the usage of attributes for organisations, organisational units
 and personal entries.
 This section briefly notes five other key issues.

2.1 Structure Rules

 A DIT structure is suggested in Annex B of X.521 [2], and it is
 recommended that Directory Pilots for White Pages services should
 follow these guidelines. Some simple restrictions should be applied,
 as described below. For further usage of the Directory like e-mail
 routing with the Directory or storage of network information in the
 Directory it will be necessary to follow the guidelines specified in
 the respective documents.
 One of the few exceptions to the basic DIT structure is, that
 international organisations will be stored immediately under the root
 of the tree. Multi-national organisations will be stored within the
 framework outlined, but with some use of aliases and attributes such
 as seeAlso to help bind together the constituent parts of these
 organisations. This is discussed in more detail in section 2.5.
 A general rule for the depth of a subtree is as follows: When a
 subtree is mainly accessed via searching, it should be as flat as
 possible to improve the performance, when the access will be mainly
 through read operations, the depth of the subtree is not a
 significant parameter for performance.

2.2 The Top Level of the DIT

 The following information will be present at the top level of the
 Participating Countries
    According to the standard the RDN is the ISO 3166 country code. In
    addition, the entries should contain suitable values of the
    friendlyCountryName attribute specified in RFC 1274. Use of this
    attribute is described in more detail in section 4.4.4.
 International Organisations
    An international organisation is an organisation, such as the
    United Nations, which inherently has a brief and scope covering
    many nations.  Such organisations might be considered to be

RARE Working Group on Network Applications Support (WG-NAP) [Page 3] RFC 1617 Naming and Structuring Guidelines for X.500 May 1994

    supra-national and this, indeed, is the raison-d'etre of such
    organisations. Such organisations will almost all be governmental
    or quasi-governmental. A multi-national organisation is an
    organisation which operates in more than one country, but is not
    supra-national. This classification includes the large commercial
    organisations whose production and sales are spread throughout a
    large number of countries.
    International organisations may be registered at the top level.
    This will not be done for multi-national organisations. Currently
    three organisations are registered so far: Inmarsat, Internet and
    North Atlantic Treaty Organization.
    A few localities will be registered under the root. The chief
    purpose of these locality entries is to provide a "natural" parent
    node for organisations which are supra-national, and yet which do
    not have global authority in their particular field. Such
    organisations will usually be governmental or quasi-governmental.
    Example localities might include: Europe, Africa, West Indies.
    Example organisations within Europe might include: European Court
    of Justice, European Space Agency, European Commission.
 DSA Information
    Some information on DSAs may be needed at the top level.  This
    should be kept to a minimum.
 The only directory information for which there is a recognised top
 level registration authority is countries. Registration of other
 information at the top level may potentially cause problems. At this
 stage, it is argued that the benefit of limiting additional top level
 registrations outweighs these problems. However, this potential
 problem should be noted by anyone making use of such a registration.

2.3 Countries

 The national standardisation bodies will define national guidelines
 for the structure of the national part of the DIT. In the interim,
 the following simple structure should suffice. The country entry will
 appear immediately beneath the root of the tree. Organisations which
 have national significance should have entries immediately beneath
 their respective country entries. Smaller organisations which are
 only known in a particular locality should be placed underneath
 locality entries representing states or similar geographical
 divisions. Entry for private persons will be listed under the
 locality entries. An example plan evolving for the US is the work of

RARE Working Group on Network Applications Support (WG-NAP) [Page 4] RFC 1617 Naming and Structuring Guidelines for X.500 May 1994

 the North American Directory Forum [3]. Another example is the
 organisation of the X.500 namespace as standardized in Australia [4].

2.4 Organisations

 Large organisations will probably need to be sub-divided by
 organisational units to help in the disambiguation of entries for
 people with common names. Entries for people and roles will be stored
 beneath organisations or organisational units.
 The organisation entry itself shall contain the information necessary
 to contact the organisation: for example, postal address, telephone
 and fax numbers.
 Although the structure of organisations often changes considerably
 over time, the aim should be to minimise the number of changes to the
 DIT. Note that renaming a superior, department entry has the effect
 of changing the DN of all subordinate entries. This has an
 undesirable impact on the service for several reasons. Alias entries
 and certain attributes or ordinary entries such as seeAlso, secretary
 and roleOccupant use DNs to maintain links with other entries. These
 references are one-way only and the Directory standard offers no
 support to automatically update all references to an entry once its
 DN changes.

2.4.1 Directory Manager, Postmaster & Secretary

 Similar to messaging, where every domain has its postmaster address
 it is highly recommended that each organisation in the X.500
 Directory has two entries: Postmaster and Directory Manager. In
 addition, Secretary entries for an organisation and its units should
 be listed. If this guidance is followed, users will benefit because
 it will be straightforward to find the right contacts for questions
 or problems with the service.
 These entries should use the object class organizationalRole with the
 roleOccupant attributes containing the distinguished names of the
 persons in charge of this role. The values
    CN=Directory Manager
 should be added as additional values whenever another language than
 English is used for the name of the entries.

RARE Working Group on Network Applications Support (WG-NAP) [Page 5] RFC 1617 Naming and Structuring Guidelines for X.500 May 1994

2.4.2 Depth of tree

 The broad recommendation for White Pages is that the DIT should be as
 flat as possible. A flat tree means that Directory names will be
 relatively short, and probably somewhat similar in length and
 component structure to paper mail addresses. A deep DIT would imply
 long Directory names, with somewhat arbitrary component parts, with a
 result which it is argued seems less natural. Any artificiality in
 the choice of names militates against successful querying.
 A presumption behind this style of naming is that most querying will
 be supported by the user specifying convenient strings of characters
 which will be mapped onto powerful search operations.  The
 alternative approach of the user browsing their way down the tree and
 selecting names from large numbers of possibilities may be more
 appropriate in some cases, and a deeper tree facilitates this.
 However, these guidelines recommend a shallow tree, and implicitly a
 search oriented approach.
 It may be considered that there are two determinants of DIT depth:
 first, how far down the DIT an organisation is placed; second, the
 structure of the DIT within organisations.
 The structure of the upper levels of the tree will be determined in
 due course by various registration authorities, and the pilot will
 have to work within the given structure. However, it is important
 that the various pilots are cognisant of what the structures are
 likely to be, and move early to adopt these structures.
 The other principal determinant of DIT depth is whether an
 organisation splits its entries over a number of organisational
 units, and if so, the number of levels. The recommendation here is
 that this sub-division of organisations is kept to a minimum. A
 maximum of two levels of organisational unit should suffice even for
 large organisations. Organisations with only a few tens or hundreds
 of employees should strongly consider not using organisational units
 at all. It is noted that there may be some problems with choice of
 unique RDNs when using a flat DIT structure. Multi-component RDNs can
 alleviate this problem: see section 3.1. The standard X.521
 recommends that an organizationalUnitName attribute can also be used
 as a naming attribute to disambiguate entries [2]. Further
 disambiguation may be achieved by the use of a personalTitle or
 userId attribute in the RDN.

RARE Working Group on Network Applications Support (WG-NAP) [Page 6] RFC 1617 Naming and Structuring Guidelines for X.500 May 1994

2.4.3 Real World Organisational Structure

 Another aspect on designing the DIT structure for an organisation is
 the administrative structure within a company. Using the same
 structure in the DIT might help in distributing maintenance authority
 to the different units. Please note comments on the stability of the
 DIT structure in section 2.4.

2.5 Multi-National Organisations

 The standard says that only international organisations may be placed
 under the root of the DIT. This implies that multi-national
 organisations must be represented as a number of separate entries
 underneath country or locality entries. This structure makes it more
 awkward to use X.500 within a multi-national to provide an internal
 organisational directory, as the data is now spread widely throughout
 the DIT, rather than all being grouped within a single sub-tree.
 Many people have expressed the view that this restriction is a severe
 limitation of X.500, and argue that the intentions of the standard
 should be ignored in this respect. This note argues, though, that the
 standard should be followed.
 No attempt to precisely define multinational organisation is essayed
 here. Instead, the observation is made that the term is applied to a
 variety of organisational structures, where an organisation operates
 in more than one country. This suggests that a variety of DIT
 structures may be appropriate to accommodate these different
 organisational structures. This document suggests three approaches,
 and notes some of the characteristics associated with each of these
 Before considering the approaches, it is worth bearing in mind again
 that a major aim in the choice of a DIT structure is to facilitate
 querying, and that approaches which militate against this should be
 avoided wherever possible.

2.5.1 The Multi-National as a Single Entity

 In many cases, a multi-national organisation will operate with a
 highly centralised structure. While the organisation may have large
 operations in a number of countries, the organisation is strongly
 controlled from the centre and the disparate parts of the
 organisation exist only as limbs of the main organisation. In such a
 situation, the model shown in figure 1 may be the best choice.

RARE Working Group on Network Applications Support (WG-NAP) [Page 7] RFC 1617 Naming and Structuring Guidelines for X.500 May 1994

                         / | \
                        /  |  \
                    C=GB  C=FR  C=US
                   /       |       \
                  /        |        \
                       /    |    \
                      /     |     \
                     /      |      \
               l=abc      ou=def     l=fgi
  1. –> means "alias to"
    Figure 1: The multi-national as a single entity
 The organisation's entries all exist under a single sub-tree. The
 organisational structure beneath the organisation entry should
 reflect the perceived structure of the organisation, and so no
 recommendations on this matter can be made here. To assist the person
 querying the directory, alias entries should be created under all
 countries where the organisation operates.

2.5.2 The Multi-National as a Loose Confederation

 Another common model of organisational structure is that where a
 multi-national consists of a number of national entities, which are
 in large part independent of both sibling national entities, and of
 any central entity. In such cases, the model shown in Figure 2 may be
 a better choice. Organisational entries exist within each country,
 and only that country's localities and organisational units appear
 directly beneath the appropriate organisational entry.

RARE Working Group on Network Applications Support (WG-NAP) [Page 8] RFC 1617 Naming and Structuring Guidelines for X.500 May 1994

                           / | \
                          /  |  \
                      C=GB C=FR C=US
                      /      |     \
                     /       |      \
            O=MultiNat   O=MultiNat   O=MultiNat
           /    |        /    |   \        |    \
          /     |       /     |    \       |     \
      L=FR    L=GB<---L=GB     |   L=US--->L=US   L=FR
        \                      |                 /
  1. –> means "alias to"
    Figure 2: The multi-national as a loose confederation
 Some binding together of the various parts of the organisation can be
 achieved by the use of aliases for localities and organisational
 units, and this can be done in a highly flexible fashion. In some
 cases, the national view might not contain all branches of the
 company, as illustrated in Figure 2.

2.5.3 Loosely Linked DIT Sub-Trees

 A third approach is to avoid aliasing altogether, and to use the
 looser binding provided by an attribute such as seeAlso. This
 approach treats all parts of an organisation as essentially separate.
 A unified view of the organisation can only be achieved by user
 interfaces choosing to follow the seeAlso links. This is a key
 difference with aliasing, where decisions to follow links may be
 specified within the protocol. (Note that it may be better to specify
 another attribute for this purpose, as seeAlso is likely to be used
 for a wide variety of purposes.)

2.5.4 Summary of Advantages and Disadvantages of the Above Approaches

 Providing an internal directory
    All the above methods can be used to provide an internal
    directory. In the first two cases, the linkage to other parts of
    the organisation can be followed by the protocol and thus
    organisation-wide searches can be achieved by single X.500

RARE Working Group on Network Applications Support (WG-NAP) [Page 9] RFC 1617 Naming and Structuring Guidelines for X.500 May 1994

    operations. In the last case, interfaces would have to "know" to
    follow the soft links indicated by the seeAlso attribute.
 Impact on naming
    In the single-entity model, all DNs within the organisation will
    be under one country. It could be argued that this will often
    result in rather "unnatural" naming. In the loose- confederation
    model, DNs are more natural, although the need to disambiguate
    between organisational units and localities on an international,
    rather than just a national, basis may have some impact on the
    choice of names. For example, it may be necessary to add in an
    extra level of organisational unit or locality information. In the
    loosely-linked model, there is no impact on naming at all.
 Views of the organisation
    The first method provides a unique view of the organisation.  The
    loose confederacy allows for a variety of views of the
    organisation. The view from the centre of the organisation may
    well be that all constituent organisations should be seen as part
    of the main organisation, whereas other parts of the organisation
    may only be interested in the organisation's centre and a few of
    its sibling organisations. The third model gives an equally
    flexible view of organisational structures.
 Lookup performance
    All methods should perform reasonably well, providing information
    is either held within a single DSA or it is replicated to the
    other DSAs.

3. Naming Style

 The first goal of naming is to provide unique identifiers for
 entries. Once this is achieved, the next major goal in naming entries
 should be to facilitate querying of the Directory. In particular,
 support for a naming structure which facilitates use of user friendly
 naming [5] is desirable. Other considerations, such as accurately
 reflecting the organisational structure of an organisation, should be
 disregarded if this has an adverse effect on normal querying. Early
 experience in the pilot has shown that a consistent approach to
 structure and naming is an aid to querying using a wide range of user
 interfaces, as interfaces are often optimised for DIT structures
 which appear prevalent. In addition, the X.501 standard notes that
 "RDNs are intended to be long-lived so that the users of the
 Directory can store the distinguished names of objects..." and "It is
 preferable that distinguished names of objects which humans have to

RARE Working Group on Network Applications Support (WG-NAP) [Page 10] RFC 1617 Naming and Structuring Guidelines for X.500 May 1994

 deal with be user-friendly." [2]
 Naming is dependent on a number of factors and these are now
 considered in turn.

3.1 Multi-Component Relative Distinguished Names

 According to the standard, relative distinguished names may have more
 than one component selected from the set of the attributes of the
 entry to be named. This is useful when there are, for example, two
 "John Smiths" in one department. The use of multi-component relative
 distinguished names allows one to avoid artificial naming values such
 as "John Smith 1" or "John Smith-2". Attributes which could be used
 as the additional naming attribute include: personalTitle,
 roomNumber, telephoneNumber, and userId.

3.2 National Guidelines for Naming

 Where naming is being done in a country which has established
 guidelines for naming, these guidelines should in general be
 followed. These guidelines might be based on an established
 registration authority, or may make use of an existing registration
 mechanism (e.g., company name registration).
 Where an organisation has a name which is nationally registered in an
 existing registry, this name is likely to be appropriate for use in
 the Directory, even in cases where there are no national guidelines.

3.3 Naming Organisation and Organisational Unit Names

 The naming of organisations in the Directory will ultimately come
 under the jurisdiction of official naming authorities. In the
 interim, it is recommended that pilots and organisations follow these
 guidelines. An organisation's RDN should usually be the full name of
 the organisation, rather than just a set of initials. This means that
 University College London should be preferred over UCL.  An example
 of the problems which a short name might cause is given by the
 proposed registration of AA for the Automobile Association.  This
 seems reasonable at first glance, as the Automobile Association is
 well known by this acronym. However, it seems less reasonable in a
 broader perspective when you consider that organisations such as
 Alcoholics Anonymous and American Airlines use the same acronym.
 Just as initials should usually be avoided for organisational RDNs,
 so should formal names which, for example, exist only on official
 charters and are not generally well known. There are two reasons for
 this approach:

RARE Working Group on Network Applications Support (WG-NAP) [Page 11] RFC 1617 Naming and Structuring Guidelines for X.500 May 1994

    1.   The names should be meaningful.
    2.   The names should uniquely identify the organisation, and be
         a name which is unlikely to be challenged in an open
         registration process. For example, UCL might well be
         challenged by United Carriers Ltd.
 The same arguments on naming style can be applied with even greater
 force to the choice of RDNs for organisational units. While
 abbreviated names will be in common parlance within an organisation,
 they will almost always be meaningless outside of that organisation.
 While many people in academic computing habitually refer to CS when
 thinking of Computer Science, CS may be given several different
 interpretations. It could equally be interpreted as Computing
 Services, Cognitive Science, Clinical Science or even Counselling
 For both organisations and organisational units, extra naming
 information should be stored in the directory as alternative values
 of the naming attribute. Thus, for University College London, UCL
 should be stored as an alternative organizationName attribute value.
 Similarly CS could be stored as an alternative organizationalUnitName
 value for Computer Science and any of the other departments cited
 earlier. In general, entries will be located by searching, and so it
 is not essential to have RDNs which are either the most memorable or
 guessable, although names should be recognisable. The need for users
 not to type long names may be achieved by use of carefully selected
 alternative values.

3.4 Naming Human Users

 A reasonably consistent approach to naming people is particularly
 critical as a large percentage of directory usage will be looking up
 information about people. User interfaces will be better able to
 assist users if entries have names conforming to a common format, or
 small group of formats. It is suggested that the RDN should follow
 such a format. Alternative values of the common name attribute should
 be used to store extra naming information. It seems sensible to try
 to ensure that the RDN commonName value is genuinely the most common
 name for a person as it is likely that user interfaces may choose to
 place greater weight on matches on the RDN than on matches on one of
 the alternative names.
 The choice of RDN for humans will be influenced by cultural
 considerations. In many countries the best choice will be of the form
 familiar-first-name surname. Thus, Steve Kille is preferred as the
 RDN choice for one of this document's co-authors, while Stephen E.
 Kille is stored as an alternative commonName value. Pragmatic choices

RARE Working Group on Network Applications Support (WG-NAP) [Page 12] RFC 1617 Naming and Structuring Guidelines for X.500 May 1994

 will have to be made for other cultures. The common name attribute
 should not be used to hold other attribute information such as
 telephone numbers, room numbers, or local codes. Such information
 should be stored within the appropriate attributes as defined in the
 COSINE and Internet X.500 Schema. Section 3.1 on multi-component RDNs
 shows how clashing names can be made unique.
 The choice of a naming strategy should not be made on the basis of
 the possibilities of the currently available user interface
 implementations. For example, it is inappropriate to use common names
 of the form 'surname firstname' merely because a user interface
 presents results in a more satisfactory order by so doing. Use the
 best structure for human names, and fix the user interface!
 More details on the use of commonName in section 4.4.1.

3.5 Application Entities

 The guidelines of X.521 should be followed, in that the application
 entity should always be named relative to an Organisation or
 Organisational Unit. The application process will often correspond to
 a system or host. In this case, the application entities should be
 named by Common Names which identify the service (e.g., "FTAM
 Service"). In cases where there is no useful distinction between
 application process and application entity, the application process
 may be omitted (This is often done for DSAs in the current pilot).

4. Attribute Values

 In general the attribute values should be used as documented in the
 standards. Sometimes the standard is not very precise about which
 attribute to use and how to represent a value.
 The following sections give recommendations how to use them in X.500
 pilot projects.

4.1 Basic Attribute Syntaxes

 Every attribute type has a definition of the attribute syntaxes its
 values may be use. Most attribute types make use the basic attribute
 syntaxes only.

RARE Working Group on Network Applications Support (WG-NAP) [Page 13] RFC 1617 Naming and Structuring Guidelines for X.500 May 1994

4.1.1 Printable String

 This most simple syntax uses a subset of characters from ISO 646 IRV.
  A-Z   a-z   0-9   '     (     )     +
  ,     -     .     /     :     ?     space
  Tab 1: Characters in PrintableString

4.1.2 IA5 String - T.50

 The International Alphabet No. 5 (IA5) is known from the X.400
 message handling service. It covers a wider range of characters than
 the printable string. The international reference version of IA5
 offers the same set of characters as ISO 646 IRV.

4.1.3 Teletex String - T.61

 The Teletex character set is a very unusual one in the computing
 environment because it uses mixed one and two octet character codes
 which are more difficult to handle than single octet codes. Most of
 the characters can be mapped to the more often supported 8-bit
 character set standard ISO 8859-1 (ISO Latin-1).

4.1.4 Case Ignore String

 Many attributes use this case insensitive syntax. It allows attribute
 values to be represented using a mixture of upper and lower case
 letters, as appropriate. Matching of attribute values, however, is
 performed such that no significance is given to case.

4.1.5 Distinguished Name

 A Distinguished Name should currently never contain a value in T.61
 string syntax because most users would not be able to view or type it
 correctly by lack of appropriate hardware/software configuration.
 Therefore, only the characters defined in printable string syntax
 should be used as part of a RDN. The correct representation of the
 name should be added as additional attribute value to match for
 search operations.

4.2 Languages & Transliteration

 The standard as available has no support at all for the use of
 different languages in the Directory. It is e.g., not possible to add
 a language qualifier to a description attribute nor is it possible to
 use characters beyond the Teletex character set.

RARE Working Group on Network Applications Support (WG-NAP) [Page 14] RFC 1617 Naming and Structuring Guidelines for X.500 May 1994

4.2.1 Languages other than English

 Many countries have more than one national language and a world-wide
 Directory must be able to support non-English-speaking users.
 Until the standard provides a solution for this problem it is
 possible to make use of multi-valued attributes to specify a value
 not only in the local languages but also in English.
 In particular the friendlyCountryName, stateOrProvinceName and
 localityName attributes should use the most often used translations
 of its original value to increase the chance for successful searches
 also for users with a foreign language. Other attributes like
 description, organizationName and organizationalUnitName attributes
 should provide multi-lingual values where appropriate.
 The drawback of this solution is, that the user interfaces present
 much redundant information because they are not able to know the
 language of the values and make an automatic selection.
 Note:   The sequence of multi-valued attribute values in an entry
         cannot be defined. It is always up to the DSA to decide on
         which order to store them and return them as results, and
         to the DUA to decide on which order to display them.

4.2.2 Transliteration

 What measures can be taken to make sure all users are able to read an
 attribute, when a value uses one of the special characters from the
 T.61 character set? An interim solution is transliteration as used in
 earlier days with the typewriters, where e.g., the German 'a' with
 umlaut is written as 'ae'. Transliteration is not necessarily unique
 since it is dependent on the language, English speakers transliterate
 the 'a' with umlaut just to an 'a'. However, it is an improvement
 over just using the T.61 value since it may not be possible to
 display such a value at all. Whenever an attribute needs a character
 not in PrintableString and the attribute syntax allows the use of the
 T.61 character set, it is recommended that the attribute should be
 supplied as multi-valued attribute both in T.61 string and in a
 transliterated PrintableString notation.

4.3 Access control

 An entry's object class attribute, and any attribute(s) used for
 naming an entry are of special significance and may be considered to
 be "structural". Any inability to access these attributes will often
 militate against successful querying of the Directory. For example,
 user interfaces typically limit the scope of their searches by

RARE Working Group on Network Applications Support (WG-NAP) [Page 15] RFC 1617 Naming and Structuring Guidelines for X.500 May 1994

 searching for entries of a particular type, where the type of entry
 is indicated by its object class. Thus, unless the intention is to
 bar public access to an entry or set of entries, the object class and
 naming attributes should be publicly readable.

4.4 Selected Attributes

 The section lists attributes together with a short description what
 they should be used for and some examples. [6] The source of the
 attributes is given in brackets.
 Note that due to national legal restrictions on privacy issues it
 might be forbidden to use certain attributes or that the search on
 them is restricted. [7]

4.4.1 Personal Attributes

 commonName [X.520]
    It is proposed that pilots should ignore the standard's
    recommendations on storing personal titles, and letters indicating
    academic and professional qualifications within the commonName
    attribute, as this overloads the commonName attribute. A
    personalTitle attribute has already been specified in the COSINE
    and Internet Schema, and another attribute could be specified for
    information about qualifications.
    The choice of a name depends on the culture as discussed in
    section 3.4. When a commonName is selected as (part of) a RDN the
    most often used form of the name should be selected. A firstname
    should never be supplied only as an initial (unless, of course,
    the source data does not include forenames). It is very important
    to have its full value in order to be able to distinguish between
    two similar entries. Sets of initials should not be concatenated
    into a single "word", but be separated by spaces and/or "."
       Format:    Firstname [Initials] Lastname
       Example:   Steve Kille
                  Stephen E. Kille
                  S.E. Kille

RARE Working Group on Network Applications Support (WG-NAP) [Page 16] RFC 1617 Naming and Structuring Guidelines for X.500 May 1994

    The use of 'Lastname Firstname' is deprecated as explained in
    section 3.4.
 favouriteDrink [RFC 1274]
    The intention of this attribute is that it provides at least one
    benign attribute which any user can create or modify, given a
    suitable user interface, without having the unfortunate impact on
    the directory service that follows from modifying an attribute
    such as an e-mail address or telephone number.
    Example: Pure Crystal Water
 organizationalStatus [RFC 1274]
    The Organisational Status attribute type specifies a category by
    which a person is often referred to in an organisation. Examples
    of usage in academia might include undergraduate student,
    researcher, lecturer, etc.
    A Directory administrator should consider carefully the
    distinctions between this and the title and description
    Example: undergraduate student
 personalTitle [RFC 1274]
    The usually used titles, especially academic ones. Excessive use
    should be avoided.
    Example: Prof. Dr.
 roomNumber [RFC 1274]
    The room where the person works, it will mostly be locally defined
    how to write the room number, e.g., Building Floor Room.
    Example: HLW B12
 secretary [RFC 1274]
    The secretary of the person. This is the Distinguished Name (DN)
    of the secretary.
    Example: CN=Beverly Pyke, O=ISODE Consortium, C=GB

RARE Working Group on Network Applications Support (WG-NAP) [Page 17] RFC 1617 Naming and Structuring Guidelines for X.500 May 1994

 surname [X.520]
    Like with commonName it is a matter of culture what to use for
    surname in case of a noble name, e.g., de Stefani, von Gunten.
    Example: Kille
 title [X.520]
    Title describing the position, job title or function of an
    organisational person.
    Example: Manager - International Sales
 userId [RFC 1274]
    When an organisation has centrally managed user ids, it might make
    sense to include it into the entry. It might also be used to form
    a unique RDN for the person.
    Example: skille
 userPassword [X.520]
    The password of the entry which allows the modification of the
    entry, provided that the access control permits it. The password
    should not be the same as any system password, unless it is sure
    that nobody can read it. With the current implementations this is
    mostly not guaranteed.
    Example: 8kiu8z7e

4.4.2 Organisational Attributes

 associatedDomain [RFC 1274]
    The Internet domain name for an organisation or one of its units.
 businessCategory [X.520]
    Type of business an organisation, an organisational unit or
    organisational person is involved in. The values could be chosen
    from a thesaurus.
    Example: Software Development

RARE Working Group on Network Applications Support (WG-NAP) [Page 18] RFC 1617 Naming and Structuring Guidelines for X.500 May 1994

 organizationName [X.520]
    The name of the organisation. The value for the RDN should be
    chosen according to section 3.3. Additional names like
    abbreviations should be used for better search results.
    Example:    Uni Lausanne
                Universite de Lausanne
                Universit\c2e Lausanne (with a T.61 encoded umlaut)
                University of Lausanne
 organizationalUnitName [X.520]
    The name of a part of the organisation. The value for the RDN
    should be chosen according to section 3.3. Additional names like
    abbreviations should be provided for better search results.
    Example:    Institut fuer Angewandte Mathematik
 roleOccupant [X.520]
    The person(s) in that role. This is the Distinguished Name of the
    entry of the person(s).
    Example: CN=Beverly Pyke, O=ISODE Consortium, C=GB
 searchGuide [X.520]
    The currently available DUAs make no use this attribute. It seems
    that it is not powerful enough for real usage. Experience is
    needed before being able to give recommendations on how to
    configure it.

4.4.3 Local Attributes

 localityName [X.520]
    Name of the place, village or town with values in local and other
    languages as useful.
    Example:    Bale
                B\c3ale (with a T.61 encoded accented character) Basel

RARE Working Group on Network Applications Support (WG-NAP) [Page 19] RFC 1617 Naming and Structuring Guidelines for X.500 May 1994

 stateOrProvinceName [X.520]
    Name of the canton, county, department, province or state with
    values in local and other languages as useful. If official and
    commonly used abbreviations exist for the states, they should be
    supplied as additional values
    Example:    Ticino

4.4.4 Miscellaneous Attributes

 audio [RFC 1274]
    The audio attribute uses a u-law encoded sound file as used by the
    "play" utility on a Sun 4. According to RFC 1274 it is an interim
    format. It may be useful to listen to the pronunciation of a name
    which is otherwise unknown.
 description [X.520]
    A short informal explanation of special interests of a person or
    organisation. Overlap with businessCategory, organizationalStatus
    and title should be avoided.
    Example: Networking, distributed systems, OSI, implementation.
 friendlyCountryName [RFC 1274]
    The friendlyCountryName attribute type specifies names of
    countries in human readable format. Especially the country name as
    used in the major languages should be included as additional
    values to help foreign users.
 jpegPhoto [RFC 1488] [8]
    A colour or grayscale picture encoded according to JPEG File
    Interchange Format (JFIF). Thanks to compression the size of the
    pictures is moderate. For persons it may show a portrait, for
    organisations the company logo or a map on how to get there.
 photo [RFC 1274]
    The photo attribute is a b/w G3 fax encoded picture of an object.
    The size of the photo should be in a sensible relation to the
    informational value of it. This attribute will be replaced by

RARE Working Group on Network Applications Support (WG-NAP) [Page 20] RFC 1617 Naming and Structuring Guidelines for X.500 May 1994

 seeAlso [X.520]
    Reference to another closely related entry in the DIT, e.g., from
    a room to the person using that room. It is the Distinguished Name
    of the entry.
    Example: CN=Beverly Pyke, O=ISODE Consortium, C=GB

4.4.5 MHS Attributes

 mhsORAddresses [X.411]
    The attribute uses internally an ASN.1 structure. The string
    notation used for display purposes is implementation dependent.
    This attribute is especially useful for an integrated X.400 user
    agent since it gets the address in a directly usable format.
 rfc822mailbox [RFC 1274]
    E-Mail address in RFC 822 notation
 textEncodedORAddress [RFC 1274]
    X.400 e-mail address in string notation. The F.401 notation should
    be used. This attribute shall disappear once the majority of the
    DUAs support the mhsORAddresses attribute. The advantage of the
    latter attribute is, that a configurable DUA could adjust the
    syntax to the one needed by the local mailer, where
    textencodedORAddress is just a string which will mostly have a
    different syntax than the mailer expects.
    Example:    G=thomas; S=lenggenhager; OU1=gate; O=switch; \
                P=switch; A=arcom; C=ch;

4.4.6 Postal Attributes

 postalAddress [X.520]
    The full postal address (but not including the name) in
    international notation, with up to 6 lines with 30 characters
    Example:    SWITCH
                Limmatquai 13
                CH-8001 Zurich

RARE Working Group on Network Applications Support (WG-NAP) [Page 21] RFC 1617 Naming and Structuring Guidelines for X.500 May 1994

 postalCode [X.520]
    The postalCode will be the same as used in the postalAddress (in
    international notation).
    Example: CH-8001
 streetAddress [X.520]
    It shall be the street where the person has its office. Mostly, it
    will be the street part of the postalAddress.
    Example: Limmatquai 138

4.4.7 Telecom Attributes

 telephoneNumber, facsimileTelephoneNumber & iSDNAddress [X.520]
    The phone number in the international notation according to CCITT
    E.123. The separator '-' instead of space may be used according to
    the local habit, it should be used consistently within a country.
    Format: "+" <country code> <national number> ["x" <extension>]
    Example: +41 1 268 1540
 telexNumber [X.520]
    The telex number in the international notation
    Example: 817379, ch, ehhg

5. Miscellany

 This section draws attention to two areas which frequently provoke
 questions, and where it is felt that a consistent approach will be

5.1 Schema consistency of aliases

 According to the letter of the standard, an alias may point at any
 entry. It is beneficial for aliases to be 'schema consistent'.
 The following two checks should be made:
    1.   The Relative Distinguished Name of the alias should use an
         attribute type normally used for naming entries of the
         object class of the main entry.

RARE Working Group on Network Applications Support (WG-NAP) [Page 22] RFC 1617 Naming and Structuring Guidelines for X.500 May 1994

    2.   If the entry (aliased object) were placed where the alias
         is, there should be no schema violation.

5.2 Organisational Units

 There is a problem that many organisations can be either
 organisations or organisational units, dependent on the location in
 the DIT (with aliases giving the alternate names). For example, an
 organisation may be an independent national organisation and also an
 organisational unit of a parent organisation. To achieve this, it is
 important to allow an entry to be of both object class organisation
 and of object class organisational unit.

6. References

 [1] Barker, P., and S. Hardcastle-Kille, "The COSINE and Internet
     X.500 schema", RFC 1274, Department of Computer Science,
     University College London, November 1991.
 [2] "The Directory --- Overview of concepts, models and services",
     CCITT X.500 Series Recommendations, December 1988.
 [3] The North American Directory Forum. "A Naming Scheme for C=US",
     RFC 1255, NADF-175, NADF, September 1991.
 [4] Michaelson, G., and M. Prior, "Naming Guidelines for the AARNet
     X.500 Directory Service", RFC 1562, AEN-001, The University of
     Queensland, The University of Adelaide, December 1993.
 [5] Hardcastle-Kille, S., "Using the OSI Directory to achieve user
     friendly naming", RFC 1484, Department of Computer Science,
     University College London, July 1993.
 [6] Barker, P., "Preparing data for inclusion in an X.500 Directory",
     Research Note RN/92/41, Department of Computer Science,
     University College London, May 1992.
 [7] Jeunink, E., and E. Huizer, "Directory Services and Privacy
     Issues", RARE WG-DATMAN, TF-LEGAL, Work in Progress, May 1993.
 [8] Howes, T., Kille, S., Yeong, W., and C. Robbins, "The X.500
     String Representation of Standard Attribute Syntaxes", RFC 1488,
     University of Michigan, ISODE Consortium, Performance Systems
     International, NeXor Ltd., July 1993.

7. Security Considerations

 Security issues are not substantially discussed in this memo.

RARE Working Group on Network Applications Support (WG-NAP) [Page 23] RFC 1617 Naming and Structuring Guidelines for X.500 May 1994

8. Authors' Addresses

 Paul Barker
 Department of Computer Science
 University College London
 Gower Street
 London WC1E 6BT
 Phone: +44 71 380 7366
 DN:  CN=Paul Barker, OU=Computer Science, O=University College
      London, C=GB
 UFN: Paul Barker, Computer Science, UCL, GB
 Steve Kille
 ISODE Consortium
 The Dome
 The Square
 Richmond TW9 1DT
 Phone: +44 81 332 9091
 DN:  CN=Steve Kille, O=ISODE Consortium, C=GB
 UFN: S. Kille, ISODE   Consortium, GB
 Thomas Lenggenhager
 Limmatquai 138
 CH-8001 Zurich
 Phone: +41 1 268 1540
 DN:  CN=Thomas Lenggenhager, O=SWITCH, C=CH
 UFN: Thomas Lenggenhager, SWITCH, CH

RARE Working Group on Network Applications Support (WG-NAP) [Page 24] RFC 1617 Naming and Structuring Guidelines for X.500 May 1994

9. Appendix - Example Entries

9.1 Country

  DN: C=CH
  objectClass=top & country & domainRelatedObject & friendlyCountry
  friendlyCountryName=Confoederatio Helvetica

9.2 Organisation

  objectClass=top & organization & mhsUser & domainRelatedObject
  description=Swiss Academic and Research Network
  organizationName=SWIss TeleCommunication system for Higher
  education\and research
  organizationName=Swiss Academic and Research Network
                Limmatquai 138
                CH-8001 Zurich
  streetAddress=Limmatquai 138
  telephoneNumber=+41 1 268 1515
  facsimileTelephoneNumber=+41 1 268 1568
  seeAlso=CN=Postmaster, O=SWITCH, C=CH
  mhsORAddresses=S=postmaster, O=switch; P=switch; A=arcom; C=ch;

RARE Working Group on Network Applications Support (WG-NAP) [Page 25] RFC 1617 Naming and Structuring Guidelines for X.500 May 1994

9.3 Organisation Unit

  DN: OU=SWITCHdirectory, O=SWITCH, C=CH
  objectClass=top & organizationalUnit
  description=The SWITCH X.500 pilot project
                Limmatquai 138
                CH-8001 Zurich
  streetAddress=Limmatquai 138
  telephoneNumber=+41 1 268 1540
  facsimileTelephoneNumber=+41 1 268 1568

9.4 Organizational Role

  DN: CN=Directory Manager, O=SWITCH, C=CH
  objectClass=top & organizationalRole & mhsUser
  commonName=Directory Manager
  description=SWITCH Directory Managers
  roleOccupant=CN=Martin Berli, O=SWITCH, C=CH
  roleOccupant=CN=Thomas Lenggenhager, O=SWITCH, C=CH
                Limmatquai 138
                CH-8001 Zurich
  streetAddress=Limmatquai 138
  telephoneNumber=+41 1 268 1540
  facsimileTelephoneNumber=+41 1 268 1568
  mhsORAddresses=S=switchinfo; O=switch; P=switch; A=arcom; C=ch;

RARE Working Group on Network Applications Support (WG-NAP) [Page 26] RFC 1617 Naming and Structuring Guidelines for X.500 May 1994

  DN: CN=Postmaster, O=SWITCH, C=CH
  objectClass=top & organizationalRole & mhsUser
  roleOccupant=CN=Christoph Graf, O=SWITCH, C=CH
  roleOccupant=CN=Felix Kugler, O=SWITCH, C=CH
  roleOccupant=CN=Marcel Parodi, O=SWITCH, C=CH
  roleOccupant=CN=Marcel Schneider, O=SWITCH, C=CH
  telephoneNumber=+41 1 268 1520
  facsimileTelephoneNumber=+41 1 268 1568
  mhsORAddresses=S=postmaster; O=switch; P=switch; A=arcom; C=ch;
  DN: CN=Secretary, O=SWITCH, C=CH
  objectClass=top & organizationalRole & quipuObject
  roleOccupant=CN=Franziska Remund, O=SWITCH, C=CH

RARE Working Group on Network Applications Support (WG-NAP) [Page 27] RFC 1617 Naming and Structuring Guidelines for X.500 May 1994

9.5 Person

  DN: CN=Thomas Lenggenhager, O=SWITCH, C=CH
  objectClass=top & person & organizationalPerson & mhsUser &
  pilotObject & newPilotPerson
  commonName=Thomas Lenggenhager
  commonName=T. Lenggenhager
  description=SWITCHinfo, Project Leader
                Limmatquai 138
                CH-8001 Zurich
  streetAddress=Limmatquai 138
  telephoneNumber=+41 1 268 1540
  facsimileTelephoneNumber=+41 1 268 1568
  mhsORAddresses=S=lenggenhager; O=switch; P=switch; A=arcom; C=ch;
  textEncodedORaddress={T.61}S=lenggenhager; O=switch; P=switch; \
                                A=arcom; C=ch;
  secretary=CN=Franziska Remund, O=SWITCH, C=CH

RARE Working Group on Network Applications Support (WG-NAP) [Page 28]

/data/webs/external/dokuwiki/data/pages/rfc/rfc1617.txt · Last modified: 1994/05/23 20:28 by

Donate Powered by PHP Valid HTML5 Valid CSS Driven by DokuWiki