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Internet Draft P. Barker Expires: April 1994 University College London S.E. Kille ISODE Consortium T. Lenggenhager SWITCH October 1993 Naming and Structuring Guidelines for X.500 Directory Pilots <draft-rare-nap-x500naming-00.txt> Status of this Memo This document is an Internet Draft. Internet Drafts are working documents of the Internet Engineering Task Force (IETF), its Areas, and its Working Groups. Note that other groups may also distribute working documents as Internet Drafts. Internet Drafts are draft documents valid for a maximum of six months. Internet Drafts may be updated, replaced, or obsoleted by other documents at any time. It is not appropriate to use Internet Drafts as reference material or to cite them other than as a "working draft" or "work in progress." Please check the I-D abstract listing contained in each Internet Draft directory to learn the current status of this or any other Internet Draft. Abstract 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. Barker, Kille & Lenggenhager Expires: April 1994 [Page 1] Internet Draft X.500 Naming Guidelines October 1993 Table Of Contents 1 Introduction ................................................. 2 2 DIT Structure ................................................ 2 2.1 Structure Rules ......................................... 2 2.2 The Top Level of the DIT ................................ 3 2.3 Countries ............................................... 4 2.4 Organisations ........................................... 4 2.5 Multinational Organisations ............................. 5 2.6 Organizational Roles .................................... 8 3 Naming Style ................................................. 9 3.1 National Guidelines for Naming .......................... 9 3.2 Naming Organisation and Organisational Unit Names ....... 9 3.3 Naming Human Users ...................................... 10 3.4 Application Entities .................................... 11 4 Attribute Values ............................................. 11 4.1 Basic Attribute Syntaxes ................................ 11 4.2 Languages & Transliteration ............................. 12 4.3 Access control .......................................... 13 4.4 Selected Attributes .................................... 14 5 Miscellany .................................................. 19 5.1 Schema consistency of aliases .......................... 19 5.2 Organisational Units ................................... 20 6 References .................................................. 20 1 Introduction As a pre-requisite to this document, it is assumed that the COSINE and Internet X.500 Schema is followed [1]. 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 three 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. Barker, Kille & Lenggenhager Expires: April 1994 [Page 2] Internet Draft X.500 Naming Guidelines October 1993 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. 2.2 The Top Level of the DIT The following information will be present at the top level of the DIT: Participating Countries According to the standard the RDN is the ISO 3166 country code [3]. 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 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. This is not a formal registration, but is adopted for the Internet Directory Service. Localities 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. Barker, Kille & Lenggenhager Expires: April 1994 [Page 3] Internet Draft X.500 Naming Guidelines October 1993 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 limited 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 standardization 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 the North American Directory Forum [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 structure of an organisation changes considerably over time, the structure of the DIT however should be as stable as possible. Changing the structure implies the change of the DNs of the entries. This may be disrupt the user service because alias entries, seeAlso attribute values but also personal alias references stored in preference files of user interfaces use the DN as reference to the original entry. 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 Depth of tree The broad recommendation 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. Barker, Kille & Lenggenhager Expires: April 1994 [Page 4] Internet Draft X.500 Naming Guidelines October 1993 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. Multiple component RDNs can alleviate this problem. 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. 2.4.2 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 Multinational 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. Barker, Kille & Lenggenhager Expires: April 1994 [Page 5] Internet Draft X.500 Naming Guidelines October 1993 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 approaches. 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 ROOT / | \ / | \ C=GB C=FR C=US / | \ / | \ O=MultiNat---->O=MultiNat<----O=MultiNat / | \ / | \ / | \ l=abc ou=def l=fgi ---> means "alias to" Figure 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. 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 for all countries where the organisation operates. Barker, Kille & Lenggenhager Expires: April 1994 [Page 6] Internet Draft X.500 Naming Guidelines October 1993 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. 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. ROOT / | \ / | \ C=GB C=FR C=US / | \ / | \ O=MultiNat O=MultiNat O=MultiNat / | / | \ | \ / | / | \ | \ L=FR L=GB<----L=GB | L=US---->L=US L=FR \ | / ------------------->L=FR<---------------- ---> means "alias to" Figure 2: The multi-national as a loose confederation 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.) Barker, Kille & Lenggenhager Expires: April 1994 [Page 7] Internet Draft X.500 Naming Guidelines October 1993 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 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. 2.6 Organizational Roles Entries with an object class of Organizational Role should be used to represent role information, such as secretaries, postmasters and directory managers. Creating separate entries for important roles makes this information more visible than it would be by simply assigning descriptive information using attributes of personal entries. Barker, Kille & Lenggenhager Expires: April 1994 [Page 8] Internet Draft X.500 Naming Guidelines October 1993 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 deal with be user-friendly." [2] Naming is dependent on a number of factors and these are now considered in turn. 3.1 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 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. 3.2 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. Barker, Kille & Lenggenhager Expires: April 1994 [Page 9] Internet Draft X.500 Naming Guidelines October 1993 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: 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 Services. 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. 3.3 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. Barker, Kille & Lenggenhager Expires: April 1994 [Page 10] Internet Draft X.500 Naming Guidelines October 1993 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 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. If such attributes have to be used to disambiguate entries, multi-component RDNs should be used, such that other attribute(s) be used for naming in addition to a common name. More details on the use of commonName in section 4.4.1. 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! 3.4 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 in 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. Barker, Kille & Lenggenhager Expires: April 1994 [Page 11] Internet Draft X.500 Naming Guidelines October 1993 4.1.1 Printable String This most simple syntax uses only characters from ISO 646 IRV. A-Z a-z 0-9 ( ) + , - . / : ? space Tab 1: Characters in PrintableString 4.1.2 Teletex String - T.61 [6] 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 8bit character set standard ISO 8859-1 (ISO Latin-1). [7] 4.1.3 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. 4.1.4 Distinguished Name A Distinguished Name should never contain a value in T.61 string syntax because many users would not be able to view or type it correctly by lack of appropriate HW/SW configuration. Therefore, only the characters defined in printable string syntax should be used as part of a RDN. 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. 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. Barker, Kille & Lenggenhager Expires: April 1994 [Page 12] Internet Draft X.500 Naming Guidelines October 1993 In particular the friendlyCountry, state and locality 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, organization and organizationalUnit 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 read an attribtue, 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 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. Barker, Kille & Lenggenhager Expires: April 1994 [Page 13] Internet Draft X.500 Naming Guidelines October 1993 4.4 Selected Attributes The section lists attributes together with a short description what they should be used for and some examples. The source of the attributes is given in brackets. [8] 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 3.3. 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 "." characters. Format: Firstname [Initials] Lastname Example: Steve Kille Stephen E. Kille S.E. Kille The use of 'Lastname Firstname' is deprecated as explained in section 3.3. favouriteDrink [RFC 1274] This is an attribute type every user may set to a value of his choice (when given modification access to the entry). It is an example of the possibilities provided by the Directory Service to expand its purpose beyond mere communication related attributes. 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. Barker, Kille & Lenggenhager Expires: April 1994 [Page 14] Internet Draft X.500 Naming Guidelines October 1993 A Directory administrator should probably consider carefully the distinctions between this and the title and description attributes. 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 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 organizational 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 List (ACL) permits it. The password should not be the same as any system password, unless it is sure that Barker, Kille & Lenggenhager Expires: April 1994 [Page 15] Internet Draft X.500 Naming Guidelines October 1993 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 organization or an organizationalUnit. Example: isode.com businessCategory [X.520] Type of business an organization, organizationalUnit or organizationalPerson is involved in. Example: Software Development organization [X.520] The name of the organization. The value for the RDN should be chosen according to section 3.2. Additional names like abbreviations should be used for better search results. Example: Uni Bern Universite de Berne Universitaet Bern University of Berne unibe organizationalUnit [X.520] The name of a part of the organization. The value for the RDN should be chosen according to section 3.2. Additional names like should be provided for better search results. Example: Institut fuer Angewandte Mathematik Mathematik iam 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 do not use this attribute. It seems that it is not powerful enough for real usage. Therefore, it is of not much use to define it. Barker, Kille & Lenggenhager Expires: April 1994 [Page 16] Internet Draft X.500 Naming Guidelines October 1993 4.4.3 Locale Attributes locality [X.520] Name of the place, village or town with values in local and other languages as useful. Example: Bale Basel Basilea Basle stateOrProvinceName [X.520] Name of the canton, county, department, province or state with values in local and other languages as useful. Example: Ticino Tessin 4.4.4 Miscellenious 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 pronounciation of a name which is otherwise unknown. description [X.520] A short explanation of the function or special interests of a person or organization. Overlap between description, organizational status and title should be avoided. Example: Expert for OSI applications. # Again this overlaps with title. 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] A color 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. Barker, Kille & Lenggenhager Expires: April 1994 [Page 17] Internet Draft X.500 Naming Guidelines October 1993 photo [RFC 1274] The photo attribute is a b/w or grayscale G3 fax encoded picture for 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 jpegPhoto. 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] [9] 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 Example: S.Kille@ISODE.com textEncodedORAdress [RFC 1274] X.400 e-mail address in string notation. The F.401 notation should be used [10]. 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 each. Example: SWITCH Limmatquai 13 CH-8001 Zurich Barker, Kille & Lenggenhager Expires: April 1994 [Page 18] Internet Draft X.500 Naming Guidelines October 1993 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 contry. Format: "+" <country code> <national number> ["x" <extension>] Example: +41 1 268 1540 telexNumber [X.520] The telex number in the international notation Example: number: 817379, country: ch, answerback: 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 useful. 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 be a valid Relative Distinguished Name of the entry. 2. If the entry (aliased object) were placed where the alias is, there should be no schema violation. Barker, Kille & Lenggenhager Expires: April 1994 [Page 19] Internet Draft X.500 Naming Guidelines October 1993 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] P. Barker and S.E. Hardcastle-Kille. The COSINE and Internet X.500 schema. Request for Comments RFC 1274, Department of Computer Science, University College London, November 1991. [2] The Directory --- Overview of concepts, models and services, December 1988. CCITT X.500 Series Recommendations. [3] ISO 3166 Country Codes. [4] The North American Directory Forum. A Naming Scheme for C=US, September 1991. Also NADF-175. [5] S.E. Hardcastle-Kille. Using the OSI Directory to achieve user friendly naming. RFC 1484, Department of Computer Science, University College London, July 1993. [6] ISO Latin-1. [8] P. Barker. Preparing data for inclusion in an X.500 Directory. Research Note RN/92/41, Department of Computer Science, University College London, May 1992. [9] CCITT X.400 Series Recommendations. [10] CCITT F.400 Series Recommendations. Security Considerations Security issues are not substantially discussed in this memo. Barker, Kille & Lenggenhager Expires: April 1994 [Page 20] Internet Draft X.500 Naming Guidelines October 1993 Authors' Addresses Paul Barker Department of Computer Science University College London Gower Street WC1E 6BT England Phone:+44-71-380-7366 EMail: P.Barker@CS.UCL.AC.UK DN: CN=Paul Barker, OU=Computer Science, O=University College London, C=GB UFN: Paul Barker, Computer Science, UCL, GB Steve Kille ISODE Consortium P.O. Box 505 London SW11 1DX England Phone:+44-71-223-4062 EMail: S.Kille@ISODE.COM DN: CN=Steve Kille, O=ISODE Consortium, C=GB UFN: S. Kille, ISODE Consortium, GB Thomas Lenggenhager SWITCH Limmatquai 138 CH-8001 Zurich Switzerland Phone:+41-1-268-1540 EMail: Lenggenhager@SWITCH.CH DN: CN=Thomas Lenggenhager, O=SWITCH, C=CH UFN: Thomas Lenggenhager, SWITCH, CH Barker, Kille & Lenggenhager Expires: April 1994 [Page 21]