ÿWPCL ûÿ2BJ|xÐ ` ÐÐÌÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿàÀ @ øÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÌÐÐ °°°è ÐÑ c܈4 PŽ ÑÐ Å°6Ø'°6Ø'Å Ð Áà=ÁÓÓÃÃCONTENTSÄă Ð ( Ð ÃÃPageÄÄ Recommendation X.402 © Message handling systems: overall architecture ................................. 1 Recommendation X.403 © Message handling systems: conformance testing ...................................... 1 Recommendation X.407 © Message handling systems: abstract service definition conventions ....................... 1 ÃÃRecommendation X.402ÄÄ ÁàX4ÁMESSAGE HANDLING SYSTEMS OVERALL ARCHITECTUREƒ The establishment in various countries of telematic services and computer©based store©and©forward message services in association with public data networks creates a need to produce standards to facilitate international message exchange between subscribers to such services. The CCITT, considering (a)ÁÀÁthe need for Message Handling Systems; (b)ÁÀÁthe need to transfer and store messages of different types; Ð Ð Ð(c)ÁÀÁthat Recommendation X.200 defines the Reference Model of Open Systems Interconnection for CCITT applications; Ð x Ð(d)ÁÀÁthat Recommendations X.208, X.217, X.218, and X.219 provide the foundation for CCITT applications; (e)ÁÀÁthat the X.500©series Recommendations define Directory Systems; (f)ÁÀÁthat Message Handling Systems are defined in a series of Recommendations: X.400, X.402, X.403, X.407, X.408, X.411, X.413, and X.419; (g)ÁÀÁthat Interpersonal Messaging is defined in Recommendations X.420 and T.330, unanimously declares (1)ÁÀÁthat the abstract models of a Message Handling System are defined in section two; (2)ÁÀÁthat the configurations of a Message Handling System are defined in section three; (3)ÁÀÁthat naming, addressing, and routing within Message Handling Systems are defined in section four. (4)ÁÀÁthat the use of the Directory by Message Handling Systems is defined in section five. (5)ÁÀÁthat the OSI realization of a Message Handling System is specified in section six. Table of Contents Section One © IntroductionÁø1Á 0.ÁàÁIntroductionÁ@ Á 1.ÁàÁScopeÁ   Á1 2.ÁàÁReferencesÁ@ Á 2.1ÁÀÁOpen Systems InterconnectionÁ$ø1Á 2.2ÁÀÁDirectory SystemsÁø1Á3 2.3ÁÀÁMessage Handling SystemsÁ ø1Á 3.ÁàÁDefinitionsÁ@ Á4 3.1ÁÀÁOpen Systems InterconnectionÁ$ø1Á 3.2ÁÀÁDirectory SystemsÁø1Á6 3.3ÁÀÁMessage Handling SystemsÁ ø1Á 4.ÁàÁAbbreviationsÁ@ Á 5.ÁàÁConventionsÁ@ Á 5.1ÁÀÁASN.1Á @ Á 5.2ÁÀÁGradeÁ @ Á 5.3ÁÀÁTermsÁ @ Á Section Two © Abstract ModelsÁø1Á 6.ÁàÁOverviewÁ @ Á8 7.ÁàÁFunctional ModelÁ@ Á 7.1ÁÀÁPrimary Functional ObjectsÁ"ø1Á 7.1.1ÁÀÁThe Message Handling SystemÁ#ø1Á 7.1.2ÁÀÁUsersÁ @ Á 7.1.3ÁÀÁDistribution ListsÁø1Á 7.2ÁÀÁSecondary Functional ObjectsÁ$ø1Á 7.2.1ÁÀÁThe Message Transfer SystemÁ#ø1Á 7.2.2ÁÀÁUser Agents 7.2.3ÁÀÁMessage Stores 7.2.4ÁÀÁAccess Units 7.3ÁÀÁTertiary Functional Objects 7.3.1ÁÀÁMessage Transfer Agents 7.4ÁÀÁSelected AU Types 7.4.1ÁÀÁPhysical Delivery 7.4.2ÁÀÁTelematic 7.4.3ÁÀÁTelex 8.ÁàÁInformation Model 8.1ÁÀÁMessages 8.2ÁÀÁProbes 8.3ÁÀÁReports 9.ÁàÁOperational Model 9.1ÁÀÁTransmittal 9.2ÁÀÁTransmittal Roles 9.3ÁÀÁTransmittal Steps 9.3.1ÁÀÁOrigination 9.3.2ÁÀÁSubmission 9.3.3ÁÀÁImport 9.3.4ÁÀÁTransfer 9.3.5ÁÀÁExport 9.3.6ÁÀÁDelivery 9.3.7ÁÀÁRetrieva 9.3.8ÁÀÁReceipt 9.4ÁÀÁTransmittal Events 9.4.1ÁÀÁSplitting 9.4.2ÁÀÁJoining 9.4.3ÁÀÁName Resolution 9.4.4ÁÀÁDL Expansion 9.4.5ÁÀÁRedirection 9.4.6ÁÀÁConversion 9.4.7ÁÀÁNon©delivery 9.4.8ÁÀÁNon©affirmation 9.4.9ÁÀÁAffirmation 9.4.10ÁÀÁRouting 10.ÁÀÁSecurity Model 10.1ÁÀÁSecurity Policies 10.2ÁÀÁSecurity Services 10.2.1ÁÀÁOrigin Authentication Security Services 10.2.2ÁÀÁSecure Access Management Security Service 10.2.3ÁÀÁData Confidentiality Security Services 10.2.4ÁÀÁData Integrity Security Services 10.2.5ÁÀÁNon©Repudiation Security Services 10.2.6ÁÀÁMessage Security Labelling Security Service 10.2.7ÁÀÁSecurity Management Services 10.3ÁÀÁSecurity Elements 10.3.1ÁÀÁAuthentication Security Elements 10.3.2ÁÀÁSecure Access Management Security Elements 10.3.3ÁÀÁData Confidentiality Security Elements 10.3.4ÁÀÁData Integrity Security Elements 10.3.5ÁÀÁNon©repudiation Security Elements 10.3.6ÁÀÁSecurity Label Security Elements 10.3.7ÁÀÁSecurity Management Security Elements 10.3.8ÁÀÁDouble Enveloping Technique Section Three © Configurations 11.ÁÀÁOverviewÁ@ Á33 12.ÁÀÁFunctional Configurations 12.1ÁÀÁRegarding the DirectoryÁø1Á 12.2ÁÀÁRegarding the Message StoreÔ ñ,ÔŒ13.ÁÀÁPhysical ConfigurationsÁø1Á 13.1ÁÀÁMessaging Systems 13.1.1ÁÀÁAccess Systems 13.1.2ÁÀÁStorage Systems 13.1.3ÁÀÁAccess and Storage Systems 13.1.4ÁÀÁTransfer Systems 13.1.5ÁÀÁAccess and Transfer Systems 13.1.6ÁÀÁStorage and Transfer Systems 13.1.7ÁÀÁAccess, Storage, and Transfer Systems 13.2ÁÀÁRepresentative Configurations 13.2.1ÁÀÁFully Centralized 13.2.2ÁÀÁCentralized Message Transfer and Storage 13.2.3ÁÀÁCentralized Message Transfer 13.2.4ÁÀÁFully Distributed 14.ÁÀÁOrganizational Configurations 14.1ÁÀÁManagement Domains 14.1.1ÁÀÁAdministration Management Domains 14.1.2ÁÀÁPrivate Management Domains 14.2ÁÀÁRepresentative Configurations 14.2.1ÁÀÁFully Centralized 14.2.2ÁÀÁDirectly Connected 14.2.3ÁÀÁIndirectly Connected 15.ÁÀÁThe Global MHS Section Four © Naming, Addressing, and Routing 16.ÁÀÁOverview 17.ÁÀÁNaming 17.1ÁÀÁDirectory Names 17.2ÁÀÁO/R Names 18.ÁÀÁAddressing 18.1ÁÀÁAttribute Lists 18.2ÁÀÁCharacter Sets 18.3ÁÀÁStandard Attributes 18.3.1ÁÀÁAdministration©domain©name 18.3.2ÁÀÁCommon©name 18.3.3ÁÀÁCountry©name 18.3.4ÁÀÁExtension©postal©O/R©address©components 18.3.5ÁÀÁExtension©physical©delivery©address©components 18.3.6ÁÀÁLocal©postal©attributes 18.3.7ÁÀÁNetwork©address 18.3.8ÁÀÁNumeric©user©identifier 18.3.9ÁÀÁOrganization©name 18.3.10Á  ÁOrganizational©unit©names 18.3.11Á  ÁPhysical©delivery©service©name 18.3.12Á  ÁPersonal©name 18.3.13Á  ÁPhysical©delivery©country©name 18.3.14Á  ÁPhysical©delivery©office©name 18.3.15Á  ÁPhysical©delivery©office©number 18.3.16Á  ÁPhysical©delivery©organization©name 18.3.17Á  ÁPhysical©delivery©personal©name 18.3.18Á  ÁPost©office©box©address 18.3.19Á  ÁPostal©code 18.3.20Á  ÁPoste©restante©address 18.3.21Á  ÁPrivate©domain©name 18.3.22Á  ÁStreet©address 18.3.23Á  ÁTerminal©identifier 18.3.24Á  ÁTerminal©type 18.3.25Á  ÁUnformatted©postal©address 18.3.26Á  ÁUnique©postal©name 18.4ÁÀÁAttribute List Equivalence 18.5ÁÀÁO/R Address Forms 18.5.1ÁÀÁMnemonic O/R Address 18.5.2ÁÀÁNumeric O/R Address 18.5.3ÁÀÁPostal O/R Address 18.5.4ÁÀÁTerminal O/R Address 18.6ÁÀÁConditional Attributes 19.ÁÀÁRouting Section Five © Use of the Directory 20.ÁÀÁOverview 21.ÁÀÁAuthentication 22.ÁÀÁName Resolution 23.ÁÀÁDL Expansion 24.ÁÀÁCapability Assessment Section Six © OSI Realization 25.ÁÀÁOverview 26.ÁÀÁApplication Service Elements 26.1ÁÀÁThe ASE Concept 26.2ÁÀÁSymmetric and Asymmetric ASEs 26.3ÁÀÁMessage Handling ASEs 26.3.1ÁÀÁMessage Transfer 26.3.2ÁÀÁMessage Submission 26.3.3ÁÀÁMessage Delivery 26.3.4ÁÀÁMessage Retrieval 26.3.5ÁÀÁMessage Administration 26.4ÁÀÁSupporting ASEs 26.4.1ÁÀÁRemote Operations 26.4.2ÁÀÁReliable Transfer 26.4.3ÁÀÁAssociation Control 27.ÁÀÁApplication Contexts Annexes AÁàÁDirectory Object Classes and Attributes A.1ÁÀÁObject Classes A.1.1ÁÀÁMHS Distribution List A.1.2ÁÀÁMHS Message Store A.1.3ÁÀÁMHS Message Transfer Agent A.1.4ÁÀÁMHS Organizational User A.1.5ÁÀÁMHS Residential User A.1.6ÁÀÁMHS User Agent A.2ÁÀÁAttributes A.2.1ÁÀÁMHS Deliverable Content Length A.2.2ÁÀÁMHS Deliverable Content Types A.2.3ÁÀÁMHS Deliverable EITs A.2.4ÁÀÁMHS DL Members A.2.5ÁÀÁMHS DL Submit Permissions A.2.6ÁÀÁMHS Message Store A.2.7ÁÀÁMHS O/R Addresses A.2.8ÁÀÁMHS Preferred Delivery Methods A.2.9ÁÀÁMHS Supported Automatic Actions A.2.10ÁÀÁMHS Supported Content Types A.2.11ÁÀÁMHS Supported Optional Attributes A.3ÁÀÁAttribute Syntaxes A.3.1ÁÀÁMHS DL Submit Permission A.3.2ÁÀÁMHS O/R Address A.3.3ÁÀÁMHS O/R Name BÁàÁReference Definition of Object Identifiers CÁàÁReference Definition of Directory Object Classes and Attributes DÁàÁSecurity Threats D.1ÁÀÁMasquerade D.2ÁÀÁMessage Sequencing D.3ÁÀÁModification of Information D.4ÁÀÁDenial of Service D.5ÁÀÁRepudiationÔ ñ,ÔŒD.6ÁÀÁLeakage of Information D.7ÁÀÁOther Threats EÁàÁProvision of Security Services in Recommendation X.411 FÁàÁDifferences Between CCITT Recommendation and ISO Standard GÁàÁIndex Section One © Introduction 0.ÁàÁIntroduction This Recommendation is one of a set of Recommendations for Message Handling. The entire set provides a comprehensive blueprint for a Message Handling System (MHS) realized by any number of cooperating open systems. The purpose of an MHS is to enable users to exchange messages on a store©and©forward basis. A message submitted on behalf of one user, the originator, is conveyed by the Message Transfer System (MTS) and subsequently delivered to the agents of one or more additional users, the recipients. Access units (AUs) link the MTS to communication systems of other kinds (e.g., postal systems). A user is assisted in the preparation, storage, and display of messages by a user agent (UA). Optionally, he is assisted in the storage of messages by a message store (MS). The MTS comprises a number of message transfer agents (MTAs) which collectively perform the store©and©forward message transfer function. This Recommendation specifies the overall architecture of the MHS and serves as a technical introduction to it. The text of this Recommendation is the subject of joint CCITT©ISO agreement. The corresponding ISO specification is ISO 10021©2. 1.ÁàÁScope This Recommendation defines the overall architecture of the MHS and serves as a technical introduction to it. Other aspects of Message Handling are specified in other Recommendations. A non©technical overview of Message Handling is provided by Recommendation X.400. The conformance testing of MHS components is described in Recommendation X.403. The conventions used in the definition of the abstract services provided by MHS components are defined in Recommendation X.407. The detailed rules by which the MTS converts the contents of messages from one EIT to another are defined in Recommendation X.408. The abstract service the MTS provides and the procedures that govern its distributed operation are defined in Recommendation X.411. The abstract service the MS provides is defined in Recommendation X.413. The application protocols that govern the interactions of MHS components are specified in Recommendation X.419. The Interpersonal Messaging System, an application of Message Handling, is defined in Recommendation X.420. Telematic access to the Interpersonal Messaging System is specified in Recommendation T.330. The CCITT Recommendations and ISO International Standards on Message Handling are summarized in Table 1/X.402. Table .T.:1/X.402 Specifications for Message Handling Systems +©©©©©©©+©©©©©©©©+©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©+ | CCITT | ISO | SUBJECT MATTER | +© Introduction ©+©©©©©©©©©©©©©©©©©©©©©©©©©ª©©©©©©©©©©©©©©©©©©+ | X.400 | 8505©1 | Service and system overview | | X.402 | 8505©2 | Overall architecture | +© Various Aspects ©©©©©ª©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©+ | X.403 | © | Conformance testing | | X.407 | 8883©2 | Abstract service definition conventions | | X.408 | © | Encoded information type conversion rules | +© Abstract Services ©©©©©©©ª©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©+ | X.411 | 8883©1 | MTS Abstract Service definition and | | procedures for distributed operation | | X.413 | TBS©1 | MS Abstract Service definition | +© Protocols ©©©©+©©©©©©©©©©©©©©ª©©©©©©©©©©©©©©©©©©©©©©©©©©©©©+ | X.419 | 8505©2 | Protocol specifications | +© Interpersonal Messaging System ©©©©©©©©©©©©©©©©©©©©©©©©©©©+ | X.420 | 9065 | Interpersonal Messaging System | | T.330 | © | Telematic access to IPMS | +©©©©©©©+©©©©©©©©+©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©ª©©+ The Directory, the principal means for disseminating communication©related information among MHS components, is defined in the X.500©series Recommendations, as summarized in Table 2/X.402. Table .T.:2/X.402 Specifications for Directories +©©©©©©©+©©©©©©©©+©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©+ | CCITT | ISO | SUBJECT MATTER | +© Model ©©©©©©©©+©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©ª©©+ | X.200 | 7498 | OSI Reference Model | +©©©©©©©+©©©©©©©©+©©©©©ª©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©+ | X.500 | 9594©1 | Overview | | X.501 | 9594©2 | Models | | X.509 | 9594©8 | Authentication framework | | X.511 | 9594©3 | Abstract service definition | | X.518 | 9594©4 | Procedures for distributed operation | | X.519 | 9594©5 | Protocol specifications | | X.520 | 9594©6 | Selected attribute types | | X.521 | 9594©7 | Selected object classes | +©©©©©©©+©©©©©ª©©©+©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©+ The architectural foundation for Message Handling is provided by still other Recommendations. The OSI Reference Model is defined in Recommendation X.200. The notation for specifying the data structures of abstract services and application protocols, ASN.1, and the associated encoding rules are defined in Recommendations X.208 and X.209. The means for establishing and releasing associations, the ACSE, is defined in Recommendations X.217 and X.227. The means for reliably conveying APDUs over associations, the RTSE, is defined in Recommendations X.218 and X.228. The means for making requests of other open systems, the ROSE, is defined in Recommendations X.219 and X.229. The CCITT Recommendations and ISO International Standards foundational to Message Handling are summarized in Table 3/X.402. Table .T.:3/X.402 Specifications for MHS Foundations +©©©©©©©+©©©©©©©©+©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©+ | CCITT | ISO | SUBJECT MATTER | +© Model ©©©©©©©©+©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©ª©©+ | X.200 | 7498 | OSI Reference Model | +© ASN.1 ©©©©©©©©+©©©©©ª©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©+ | X.208 | 8824 | Abstract syntax notation | | X.209 | 8825 | Basic encoding rules | +© Association Control ©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©+ | X.217 | 8649 | Service definition | | X.227 | 8650 | Protocol specification | +© Reliable Transfer ©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©+ | X.218 | 9066/1 | Service definition | | X.228 | 9066/2 | Protocol specification | +© Remote Operations ©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©+ | X.219 | 9072/1 | Service definition | | X.229 | 9072/2 | Protocol specification | +©©©©©©©+©©ª©©©©©©+©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©+ This Recommendation is structured as follows. Section one is this introduction. Section two presents abstract models of Message Handling. Section three specifies how one can configure the MHS to satisfy any of a variety of functional, physical, and organizational requirements. Section four describes the naming and addressing of users and distribution lists and the routing of information objects to them. Section five describes the uses the MHS may make of the Directory. Section six describes how the MHS is realized by means of OSI. Annexes provide important supplemental information. No requirements for conformance to this Recommendation are imposed. 2.ÁàÁReferences This Recommendation and others in the set cite the documents below. 2.1ÁÀÁOpen Systems Interconnection This Recommendation and others in the set cite the following OSI specifications: X.200ÁÀÁBasic reference model.(see also ISO 7498). X.208ÁÀÁSpecification of abstract syntax notation one (ASN.1) (see also ISO 8824). X.209ÁÀÁSpecification of basic encoding rules for abstract syntax notation one (ASN.1) (see also ISO 8825). X.217ÁÀÁAssociation control: Service definition (see also ISO 8649). X.218ÁÀÁReliable transfer: Model and service definition (see also ISO 9066©1). X.219ÁÀÁRemote operations: Model, notation and service definition (see also ISO 9072©1). X.227ÁÀÁAssociation control: Protocol specification (see also ISO 8650). X.228ÁÀÁReliable transfer: Protocol specification (see also ISO 9066©2). X.229ÁÀÁRemote operations: Protocol specification (see also ISO 9072©2). 2.2 Directory Systems This Recommendation and others in the set cite the following Directory System specifications: of concepts, models, and service.) X.500ÁÀÁThe directory Overview (see also ISO 9594©1).Ô ñ,ÔŒX.501ÁÀÁThe directory Models (see also ISO 9594©2). X.509ÁÀÁThe directory Authentication framework (see also ISO 9594©8). X.511ÁÀÁThe directory Abstract service definition (see also ISO 9594©3). X.518ÁÀÁThe directory Procedures for distributed operation (see also ISO 9594©4). X.519ÁÀÁThe directory Protocol specifications (see also ISO 9495©5). X.520ÁÀÁThe directory Selected attribute types (see also ISO 9495©6). X.521ÁÀÁThe directory Selected object classes (see also ISO 9495©7). 2.3ÁÀÁMessage Handling Systems This Recommendation and others in the set cite the following Message Handling System specifications: T.330ÁÀÁTelematic access to IPMS. X.400ÁÀÁMessage handling: Service and system overview (see also ISO 10021©1). X.403ÁÀÁMessage handling systems: Conformance testing. X.407ÁÀÁMessage handling systems: Abstract service definition conventions (see also ISO 10021©3). X.408ÁÀÁMessage handling systems: Encoded information type conversion rules. X.411ÁÀÁMessage handling systems: Message transfer system: Abstract service definition and procedures (see also ISO 10021©4). X.413ÁÀÁMessage handling systems: Message store: Abstract service definition (see also ISO 1002105). X.419ÁÀÁMessage handling systems: Protocol specifications (see also ISO 10021©6). X.420ÁÀÁMessage handling systems: Interpersonal messaging system (see also ISO 10021©7). 3.ÁàÁDefinitions For the purposes of this Recommendation and others in the set, the definitions below apply. 3.1ÁÀÁOpen Systems Interconnection This Recommendation and others in the set use the following terms defined in Recommendation X.200, as well as the names of the seven layers of the Reference Model: a)ÁàÁabstract syntax; b)ÁàÁapplication entity (.I.ab:AE;); c)ÁàÁapplication process; d)ÁàÁapplication protocol data unit (.I.ab:APDU;); e)ÁàÁapplication service element (.I.ab:ASE;); f)ÁàÁdistributed information processing task; g)ÁàÁlayer; h)ÁàÁopen system; i)ÁàÁOpen Systems Interconnection (.I.ab:OSI;); j)ÁàÁpeer; k)ÁàÁpresentation context; l)ÁàÁprotocol; m)ÁàÁReference Model; n)ÁàÁtransfer syntax; and o)ÁàÁuser element (.I.ab:UE;). This Recommendation and others in the set use the following terms defined in Recommendations X.208 and X.209, as well as the names of ASN.1 data types and values: a)ÁàÁAbstract Syntax Notation One (.I.ab:ASN.1;); b)ÁàÁBasic Encoding Rules; c)ÁàÁexplicit; d)ÁàÁexport; e)ÁàÁimplicit; f)ÁàÁimport; g)ÁàÁmacro; h)ÁàÁmodule; i)ÁàÁtag; j)ÁàÁtype; and k)ÁàÁvalue. This Recommendation and others in the set use the following terms defined in Recommendation X.217: a)ÁàÁapplication association; association; b)ÁàÁapplication context (.I.ab:AC;); c)ÁàÁAssociation Control Service Element (.I.ab:ACSE;); d)ÁàÁinitiator; and e)ÁàÁresponder. This Recommendation and others in the set use the following terms defined in Recommendation X.218: a)ÁàÁReliable Transfer (.I.ab:RT;); and b)ÁàÁReliable Transfer Service Element (.I.ab:RTSE;). This Recommendation and others in the set use the following terms defined in Recommendation X.219: a)ÁàÁargument; b)ÁàÁasynchronous; c)ÁàÁbind; d)ÁàÁparameter; e)ÁàÁremote error; f)ÁàÁremote operation; g)ÁàÁRemote Operations (.I.ab:RO;); h)ÁàÁRemote Operations Service Element (.I.ab:ROSE;); i)ÁàÁresult; j)ÁàÁsynchronous; and k)ÁàÁunbind. 3.2ÁÀÁDirectory Systems This Recommendation and others in the set use the following terms defined in the X.500©series Recommendations: a)ÁàÁattribute; b)ÁàÁcertificate; c)ÁàÁcertification authority; d)ÁàÁcertification path; e)ÁàÁdirectory entry; entry; f)ÁàÁdirectory system agent (.I.ab:DSA;); g)ÁàÁDirectory; h)ÁàÁhash function; i)ÁàÁname; j)ÁàÁobject class; k)ÁàÁobject; l)ÁàÁsimple authentication; and m)ÁàÁstrong authentication. 3.3ÁÀÁMessage Handling Systems For the purposes of this Recommendation and others in the set, the definitions indexed in annex G apply. 4.ÁàÁAbbreviations For the purposes of this Recommendation and others in the set, the abbreviations indexed in annex G apply. 5.ÁàÁConventions This Recommendation uses the descriptive conventions identified below. 5.1ÁÀÁASN.1 This Recommendation uses several ASN.1©based descriptive conventions in annexes A and C to define the Message Handling©specific information the Directory may hold. In particular, it uses the OBJECT©CLASS, ATTRIBUTE, and ATTRIBUTE©SYNTAX macros of Recommendation X.501 to define Message Handling©specific object classes, attributes, and attribute syntaxes. ASN.1 appears both in annex A to aid the exposition, and again, largely redundantly, in annex C for reference. If differences are found between the two, a specification error is indicated. Note that ASN.1 tags are implicit throughout the ASN.1 module that annex C defines; the module is definitive in that respect. 5.2ÁÀÁGrade Whenever this Recommendation describes a class of data structure (e.g., O/R addresses) having components (e.g., attributes), each component is assigned one of theÔ ñ,Ô following .I.gl:grade;s: a)ÁàÁ.I.gl:mandatory; (.I.ab:M;): A mandatory component shall be present in every instance of the class. b)ÁàÁ.I.gl:optional; (.I.ab:O;): An optional component shall be present in an instance of the class at the discretion of the object (e.g., user) supplying that instance. There is no default value. c)ÁàÁ.I.gl:defaultable; (.I.ab:D;): A defaultable component shall be present in an instance of the class at the discretion of the object (e.g., user) supplying that instance. In its absence a default value, specified by this Recommendation, applies. d)ÁàÁ.I.gl:conditional; (.I.ab:C;): A conditional component shall be present in an instance of the class as dictated by this Recommendation. 5.3ÁÀÁTerms Throughout the remainder of this Recommendation, terms are rendered in bold when defined, in italic when referenced prior to their definitions, without emphasis upon other occasions. Terms that are proper nouns are capitalized, generic terms are not.