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'SASL' -- No information found for draft-ietf-ldapbis-syntaxes-xx - is the name correct? -- Possible downref: Normative reference to a draft: ref. 'Syntaxes' -- No information found for draft-ietf-ldapbis-user-schema-xx - is the name correct? -- Possible downref: Normative reference to a draft: ref. 'Schema' -- Possible downref: Non-RFC (?) normative reference: ref. 'Unicode' Summary: 7 errors (**), 0 flaws (~~), 5 warnings (==), 30 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 INTERNET-DRAFT Editor: Kurt D. Zeilenga 3 Intended Category: Standard Track OpenLDAP Foundation 4 Expires in six months 4 June 2004 5 Obsoletes: RFC 2251, RFC 2252, RFC 2256 7 LDAP: Directory Information Models 8 10 Status of this Memo 12 This document is intended to be published as a Standard Track RFC. 13 Distribution of this memo is unlimited. Technical discussion of this 14 document will take place on the IETF LDAP Revision Working Group 15 mailing list . Please send editorial 16 comments directly to the editor . 18 By submitting this Internet-Draft, I accept the provisions of Section 19 4 of RFC 3667. By submitting this Internet-Draft, I certify that any 20 applicable patent or other IPR claims of which I am aware have been 21 disclosed, and any of which I become aware will be disclosed, in 22 accordance with RFC 3668. 24 Internet-Drafts are working documents of the Internet Engineering Task 25 Force (IETF), its areas, and its working groups. Note that other 26 groups may also distribute working documents as Internet-Drafts. 28 Internet-Drafts are draft documents valid for a maximum of six months 29 and may be updated, replaced, or obsoleted by other documents at any 30 time. It is inappropriate to use Internet-Drafts as reference material 31 or to cite them other than as "work in progress." 33 The list of current Internet-Drafts can be accessed at 34 http://www.ietf.org/ietf/1id-abstracts.txt. The list of 35 Internet-Draft Shadow Directories can be accessed at 36 http://www.ietf.org/shadow.html. 38 Copyright (C) The Internet Society (2004). All Rights Reserved. 40 Please see the Full Copyright section near the end of this document 41 for more information. 43 Abstract 45 The Lightweight Directory Access Protocol (LDAP) is an Internet 46 protocol for accessing distributed directory services which act in 47 accordance with X.500 data and service models. This document 48 describes the X.500 Directory Information Models, as used in LDAP. 50 Table of Contents 52 Status of this Memo 1 53 Abstract 2 54 Table of Contents 55 1. Introduction 3 56 1.1. Relationship to Other LDAP Specifications 57 1.2. Relationship to X.501 4 58 1.3. Conventions 59 1.4. Common ABNF Productions 60 2. Model of Directory User Information 6 61 2.1. The Directory Information Tree 7 62 2.2. Structure of an Entry 63 2.3. Naming of Entries 8 64 2.4. Object Classes 9 65 2.5. Attribute Descriptions 12 66 2.6. Alias Entries 15 67 3. Directory Administrative and Operational Information 17 68 3.1. Subtrees 69 3.2. Subentries 70 3.3. The 'objectClass' attribute 18 71 3.4. Operational attributes 19 72 4. Directory Schema 20 73 4.1. Schema Definitions 23 74 4.2. Subschema Subentries 30 75 4.3. 'extensibleObject' 35 76 4.4. Subschema Discovery 77 5. DSA (Server) Informational Model 36 78 5.1. Server-specific Data Requirements 79 6. Other Considerations 39 80 6.1. Preservation of User Information 40 81 6.2. Short Names 82 6.3. Cache and Shadowing 41 83 7. Implementation Guidelines 84 7.1. Server Guidelines 85 7.2. Client Guidelines 86 8. Security Considerations 42 87 9. IANA Considerations 88 10. Acknowledgments 43 89 11. Editor's Address 90 12. References 44 91 12.1. Normative References 92 12.2. Informative References 45 93 Appendix A. Changes 94 Intellectual Property Rights 50 95 Full Copyright 97 1. Introduction 99 This document discusses the X.500 Directory Information Models 100 [X.501], as used by the Lightweight Directory Access Protocol (LDAP) 101 [Roadmap]. 103 The Directory is "a collection of open systems cooperating to provide 104 directory services" [X.500]. The information held in the Directory is 105 collectively known as the Directory Information Base (DIB). A 106 Directory user, which may be a human or other entity, accesses the 107 Directory through a client (or Directory User Agent (DUA)). The 108 client, on behalf of the directory user, interacts with one or more 109 servers (or Directory System Agents (DSA)). A server holds a fragment 110 of the DIB. 112 The DIB contains two classes of information: 114 1) user information (e.g., information provided and administrated 115 by users). Section 2 describes the Model of User Information. 117 2) administrative and operational information (e.g., information 118 used to administer and/or operate the directory). Section 3 119 describes the model of Directory Administrative and Operational 120 Information. 122 These two models, referred to as the generic Directory Information 123 Models, describe how information is represented in the Directory. 124 These generic models provide a framework for other information models. 125 Section 4 discusses the subschema information model and subschema 126 discovery. Section 5 discusses the DSA (Server) Informational Model. 128 Other X.500 information models, such as access control distribution 129 knowledge, and replication knowledge information models, may be 130 adapted for use in LDAP. Specification of how these models apply to 131 LDAP is left to future documents. 133 1.1. Relationship to Other LDAP Specifications 135 This document is a integral part of the LDAP technical specification 136 [Roadmap] which obsoletes the previously defined LDAP technical 137 specification, RFC 3377, in its entirety. 139 This document obsoletes RFC 2251 sections 3.2 and 3.4, as well as 140 portions of sections 4 and 6. Appendix A.1 summaries changes to these 141 sections. The remainder of RFC 2251 is obsoleted by the [Protocol], 142 [AuthMeth], and [Roadmap] documents. 144 This document obsoletes RFC 2252 sections 4, 5 and 7. Appendix A.2 145 summaries changes to these sections. The remainder of RFC 2252 is 146 obsoleted by [Syntaxes]. 148 This document obsoletes RFC 2256 sections 5.1, 5.2, 7.1 and 7.2. 149 Appendix A.3 summarizes changes to these sections. The remainder of 150 RFC 2256 is obsoleted by [Schema] and [Syntaxes]. 152 1.2. Relationship to X.501 154 This document includes material, with and without adaptation, from 155 [X.501]. The material in this document takes precedence over that in 156 [X.501]. 158 1.3. Conventions 160 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 161 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 162 document are to be interpreted as described in BCP 14 [RFC2119]. 164 Schema definitions are provided using LDAP description formats (as 165 defined in Section 4.1). Definitions provided here are formatted 166 (line wrapped) for readability. Matching rules and LDAP syntaxes 167 referenced in these definitions are specified in [Syntaxes]. 169 1.4. Common ABNF Productions 171 A number of syntaxes in this document are described using Augmented 172 Backus-Naur Form (ABNF) [RFC2234]. These syntaxes (as well as a 173 number of syntaxes defined in other documents) rely on the following 174 common productions: 176 keystring = leadkeychar *keychar 177 leadkeychar = ALPHA 178 keychar = ALPHA / DIGIT / HYPHEN 179 number = DIGIT / ( LDIGIT 1*DIGIT ) 181 ALPHA = %x41-5A / %x61-7A ; "A"-"Z" / "a"-"z" 182 DIGIT = %x30 / LDIGIT ; "0"-"9" 183 LDIGIT = %x31-39 ; "1"-"9" 184 HEX = DIGIT / %x41-46 / %x61-66 ; "0"-"9" / "A"-"F" / "a"-"f" 186 SP = 1*SPACE ; one or more " " 187 WSP = 0*SPACE ; zero or more " " 189 NULL = %x00 ; null (0) 190 SPACE = %x20 ; space (" ") 191 DQUOTE = %x22 ; quote (""") 192 SHARP = %x23 ; octothorpe (or sharp sign) ("#") 193 DOLLAR = %x24 ; dollar sign ("$") 194 SQUOTE = %x27 ; single quote ("'") 195 LPAREN = %x28 ; left paren ("(") 196 RPAREN = %x29 ; right paren (")") 197 PLUS = %x2B ; plus sign ("+") 198 COMMA = %x2C ; comma (",") 199 HYPHEN = %x2D ; hyphen ("-") 200 DOT = %x2E ; period (".") 201 SEMI = %x3B ; semicolon (";") 202 LANGLE = %x3C ; left angle bracket ("<") 203 EQUALS = %x3D ; equals sign ("=") 204 RANGLE = %x3E ; right angle bracket (">") 205 ESC = %x5C ; backslash ("\") 206 USCORE = %x5F ; underscore ("_") 207 LCURLY = %x7B ; left curly brace "{" 208 RCURLY = %x7D ; right curly brace "}" 210 ; Any UTF-8 [UTF-8] encoded Unicode [Unicode] character 211 UTF8 = UTF1 / UTFMB 212 UTFMB = UTF2 / UTF3 / UTF4 213 UTF0 = %x80-BF 214 UTF1 = %x00-7F 215 UTF2 = %xC2-DF UTF0 216 UTF3 = %xE0 %xA0-BF UTF0 / %xE1-EC 2(UTF0) / 217 %xED %x80-9F UTF0 / %xEE-EF 2(UTF0) 218 UTF4 = %xF0 %x90-BF 2(UTF0) / %xF1-F3 3(UTF0) / 219 %xF4 %x80-8F 2(UTF0) 221 OCTET = %x00-FF ; Any octet (8-bit data unit) 223 Object identifiers (OIDs) [X.680] are represented in LDAP using a 224 dot-decimal format conforming to the ABNF: 226 numericoid = number 1*( DOT number ) 228 Short names, also known as descriptors, are used as more readable 229 aliases for object identifiers. Short names are case insensitive and 230 conform to the ABNF: 232 descr = keystring 234 Where either an object identifier or a short name may be specified, 235 the following production is used: 237 oid = descr / numericoid 239 While the form is generally preferred when the usage is 240 restricted to short names referring to object identifiers which 241 identify like kinds of objects (e.g., attribute type descriptions, 242 matching rule descriptions, object class descriptions), the 243 form should be used when the object identifiers may 244 identify multiple kinds of objects or when an unambiguous short name 245 (descriptor) is not available. 247 Implementations SHOULD treat short names (descriptors) used in an 248 ambiguous manner (as discussed above) as unrecognized. 250 Short Names (descriptors) are discussed further in Section 6.2. 252 2. Model of Directory User Information 254 As [X.501] states: 256 The purpose of the Directory is to hold, and provide access to, 257 information about objects of interest (objects) in some 'world'. 258 An object can be anything which is identifiable (can be named). 260 An object class is an identified family of objects, or conceivable 261 objects, which share certain characteristics. Every object belongs 262 to at least one class. An object class may be a subclass of other 263 object classes, in which case the members of the former class, the 264 subclass, are also considered to be members of the latter classes, 265 the superclasses. There may be subclasses of subclasses, etc., to 266 an arbitrary depth. 268 A directory entry, a named collection of information, is the basic 269 unit of information held in the Directory. There are multiple kinds 270 of directory entries. 272 An object entry represents a particular object. An alias entry 273 provides alternative naming. A subentry holds administrative and/or 274 operational information. 276 The set of entries representing the DIB are organized hierarchically 277 in a tree structure known as the Directory Information Tree (DIT). 279 Section 2.1 describes the Directory Information Tree 280 Section 2.2 discusses the structure of entries. 281 Section 2.3 discusses naming of entries. 282 Section 2.4 discusses object classes. 283 Section 2.5 discusses attribute descriptions. 284 Section 2.6 discusses alias entries. 286 2.1. The Directory Information Tree 288 As noted above, the DIB is composed of a set of entries organized 289 hierarchically in a tree structure known as the Directory Information 290 Tree (DIT). Specifically, a tree where vertices are the entries. 292 The arcs between vertices define relations between entries. If an arc 293 exists from X to Y, then the entry at X is the immediate superior of Y 294 and Y is the immediate subordinate of X. An entry's superiors are the 295 entry's immediate superior and its superiors. An entry's subordinates 296 are all of its immediate subordinates and their subordinates. 298 Similarly, the superior/subordinate relationship between object 299 entries can be used to derive a relation between the objects they 300 represent. DIT structure rules can be used to govern relationships 301 between objects. 303 Note: An entry's immediate superior is also known as the entry's 304 parent and an entry's immediate subordinate is also known as the 305 entry's child. Entries which have the same parent are known as 306 siblings. 308 2.2. Structure of an Entry 310 An entry consists of a set of attributes which hold information about 311 the object which the entry represents. Some attributes represent user 312 information and are called user attributes. Other attributes 313 represent operational and/or administrative information and are called 314 operational attributes. 316 An attribute is an attribute description (a type and zero or more 317 options) with one or more associated values. An attribute is often 318 referred to by its attribute description. For example, the 319 'givenName' attribute is the attribute which consists of the attribute 320 description 'givenName' (the 'givenName' attribute type [Schema] and 321 zero options) and one or more associated values. 323 The attribute type governs whether the attribute can have multiple 324 values, the syntax and matching rules used to construct and compare 325 values of that attribute, and other functions. Options indicate 326 subtypes and other functions. 328 Attribute values conform to the defined syntax of the attribute type. 330 No two values of an attribute may be equivalent. Two values are 331 considered equivalent only if they would match according to the 332 equality matching rule of the attribute type. If the attribute type 333 is defined with no equality matching rule, two values are equivalent 334 if and only if they are identical. 336 For example, a 'givenName' attribute can have more than one value, 337 they must be Directory Strings, and they are case insensitive. A 338 'givenName' attribute cannot hold both "John" and "JOHN" as these are 339 equivalent values per the equality matching rule of the attribute 340 type. 342 When an attribute is used for naming of the entry, one and only one 343 value of the attribute is used in forming the Relative Distinguished 344 Name. This value is known as a distinguished value. 346 2.3. Naming of Entries 348 2.3.1. Relative Distinguished Names 350 Each entry is named relative to its immediate superior. This relative 351 name, known as its Relative Distinguished Name (RDN) [X.501], is 352 composed of an unordered set of one or more attribute value assertions 353 (AVA) consisting of an attribute description with zero options and an 354 attribute value. These AVAs are chosen to match attribute values 355 (each a distinguished value) of the entry. 357 An entry's relative distinguished name must be unique among all 358 immediate subordinates of the entry's immediate superior (i.e., all 359 siblings). 361 The following are examples of string representations of RDNs [LDAPDN]: 363 UID=12345 364 OU=Engineering 365 CN=Kurt Zeilenga+L=Redwood Shores 367 The last is an example of a multi-valued RDN. That is, an RDN 368 composed of multiple AVAs. 370 2.3.2. Distinguished Names 372 An entry's fully qualified name, known as its Distinguished Name (DN) 373 [X.501], is the concatenation of its RDN and its immediate superior's 374 DN. A Distinguished Name unambiguously refers to an entry in the 375 tree. The following are examples of string representations of DNs 376 [LDAPDN]: 378 UID=nobody@example.com,DC=example,DC=com 379 CN=John Smith,OU=Sales,O=ACME Limited,L=Moab,ST=Utah,C=US 381 2.3.3. Alias Names 383 An alias, or alias name, is "an name for an object, provided by the 384 use of alias entries" [X.501]. Alias entries are described in Section 385 2.6. 387 2.4. Object Classes 389 An object class is "an identified family of objects (or conceivable 390 objects) which share certain characteristics" [X.501]. 392 As defined in [X.501]: 394 Object classes are used in the Directory for a number of purposes: 396 - describing and categorising objects and the entries that 397 correspond to these objects; 399 - where appropriate, controlling the operation of the Directory; 401 - regulating, in conjunction with DIT structure rule 402 specifications, the position of entries in the DIT; 404 - regulating, in conjunction with DIT content rule 405 specifications, the attributes that are contained in entries; 407 - identifying classes of entry that are to be associated with a 408 particular policy by the appropriate administrative authority. 410 An object class (a subclass) may be derived from an object class 411 (its direct superclass) which is itself derived from an even more 412 generic object class. For structural object classes, this process 413 stops at the most generic object class, 'top' (defined in Section 414 2.4.1). An ordered set of superclasses up to the most superior 415 object class of an object class is its superclass chain. 417 An object class may be derived from two or more direct 418 superclasses (superclasses not part of the same superclass chain). 419 This feature of subclassing is termed multiple inheritance. 421 Each object class identifies the set of attributes required to be 422 present in entries belonging to the class and the set of attributes 423 allowed to be present in entries belonging to the class. As an entry 424 of a class must meet the requirements of each class it belongs to, it 425 can be said that an object class inherits the sets of allowed and 426 required attributes from its superclasses. A subclass can identify an 427 attribute allowed by its superclass as being required. If an 428 attribute is a member of both sets, it is required to be present. 430 Each object class is defined to be one of three kinds of object 431 classes: Abstract, Structural, or Auxiliary. 433 Each object class is identified by an object identifier (OID) and, 434 optionally, one or more short names (descriptors). 436 2.4.1. Abstract Object Classes 438 An abstract object class, as the name implies, provides a base of 439 characteristics from which other object classes can be defined to 440 inherit from. An entry cannot belong to an abstract object class 441 unless it belongs to a structural or auxiliary class which inherits 442 from that abstract class. 444 Abstract object classes can not derive from structural nor auxiliary 445 object classes. 447 All structural object classes derive (directly or indirectly) from the 448 'top' abstract object class. Auxiliary object classes do not 449 necessarily derive from 'top'. 451 The following is the object class definition (see Section 4.1.1) for 452 the 'top' object class: 454 ( 2.5.6.0 NAME 'top' ABSTRACT MUST objectClass ) 456 All entries belong to the 'top' abstract object class. 458 2.4.2. Structural Object Classes 460 As stated in [X.501]: 462 An object class defined for use in the structural specification of 463 the DIT is termed a structural object class. Structural object 464 classes are used in the definition of the structure of the names 465 of the objects for compliant entries. 467 An object or alias entry is characterised by precisely one 468 structural object class superclass chain which has a single 469 structural object class as the most subordinate object class. 470 This structural object class is referred to as the structural 471 object class of the entry. 473 Structural object classes are related to associated entries: 475 - an entry conforming to a structural object class shall 476 represent the real-world object constrained by the object 477 class; 479 - DIT structure rules only refer to structural object classes; 480 the structural object class of an entry is used to specify the 481 position of the entry in the DIT; 483 - the structural object class of an entry is used, along with an 484 associated DIT content rule, to control the content of an 485 entry. 487 The structural object class of an entry shall not be changed. 489 Each structural object class is a (direct or indirect) subclass of the 490 'top' abstract object class. 492 Structural object classes cannot subclass auxiliary object classes. 494 Each entry is said to belong to its structural object class as well as 495 all classes in its structural object class's superclass chain. 497 2.4.3. Auxiliary Object Classes 499 Auxiliary object classes are used augment the characteristics of 500 entries. They are commonly used to augment the sets of attributes 501 required and allowed to be present in an entry. They can be used to 502 describe entries or classes of entries. 504 Auxiliary object classes cannot subclass structural object classes. 506 An entry can belong to any subset of the set of auxiliary object 507 classes allowed by the DIT content rule associated with the structural 508 object class of the entry. If no DIT content rule is associated with 509 the structural object class of the entry, the entry cannot belong to 510 any auxiliary object class. 512 The set of auxiliary object classes which an entry belongs to can 513 change over time. 515 2.5. Attribute Descriptions 517 An attribute description is composed of an attribute type (see Section 518 2.5.1) and a set of zero or more attribute options (see Section 519 2.5.2). 521 An attribute description is represented by the ABNF: 523 attributedescription = attributetype options 524 attributetype = oid 525 options = *( SEMI option ) 526 option = 1*keychar 528 where identifies the attribute type and each