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rfc:rfc2714

Network Working Group V. Ryan Request for Comments: 2714 R. Lee Category: Informational S. Seligman

                                                Sun Microsystems, Inc.
                                                          October 1999
Schema for Representing CORBA Object References in an LDAP Directory

Status of this Memo

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

Copyright Notice

 Copyright (C) The Internet Society (1999).  All Rights Reserved.

Abstract

 CORBA [CORBA] is the Common Object Request Broker Architecture
 defined by the Object Management Group. This document defines the
 schema for representing CORBA object references in an LDAP directory
 [LDAPv3].

1. Introduction

 This document assumes that the reader has a general understanding of
 CORBA.
 Traditionally, LDAP directories have been used to store data. Users
 and programmers think of the directory as a hierarchy of directory
 entries, each containing a set of attributes.  You look up an entry
 from the directory and extract the attribute(s) of interest.  For
 example, you can look up a person's telephone number from the
 directory.  Alternatively, you can search the directory for entries
 with a particular set of attributes.  For example, you can search for
 all persons in the directory with the surname "Smith".
 CORBA applications require access to CORBA objects. Traditionally,
 CORBA applications have used the COS Naming service for storage and
 retrieval of CORBA object references. When deployed in environments
 with a directory, CORBA applications should be able to use the
 directory as a repository for CORBA object references. The directory
 provides a centrally administered, and possibly replicated, service
 for use by CORBA applications distributed across the network.

Ryan, et al. Informational [Page 1] RFC 2714 Schema for CORBA Object References October 1999

 For example, an application server may use the directory for
 "registering" CORBA objects representing the services that it
 manages, so that a client can later search the directory to locate
 those services as it needs.
 The motivation for this document is to define a common way for
 applications to store and retrieve CORBA object references from the
 directory.  Using this common schema, any CORBA application that
 needs to read or store CORBA object references in the directory can
 do so in an interoperable way.
 Note that this schema is defined for storing CORBA "object
 references," not CORBA objects in general. There might be other ways
 to store CORBA objects in an LDAP directory but they are not covered
 by this schema.

2. Representation of CORBA Object References

 This document defines schema elements to represent a CORBA object
 reference in LDAP directory. Applications in possession of a
 reference to an object can invoke calls on that object.  Such a
 reference is termed an "interoperable object reference," or IOR.
 Access to CORBA objects by using IORs is achieved transparently to
 the application, by means of the General Inter-ORB Protocol.
 A CORBA object reference is represented in the directory by the
 object class corbaObjectReference. corbaObjectReference is a subclass
 of the abstract corbaObject object class. corbaObjectReference is an
 auxiliary object class, which means that it needs to be mixed in with
 a structural object class.
 The object class corbaContainer is used in a directory entry which
 represents a CORBA object or object reference. It is a structural
 object class, and when representing an object reference, the
 corbaObjectReference object class would also need to be present in
 the entry.  corbaContainer is not required when a subclass of
 corbaObject (such as corbaObjectReference) is mixed in with another
 structural object class.
 The definitions for the object classes corbaObject,
 corbaObjectReference, and corbaContainer are presented in Section 4.
 The corbaObject class has two optional attributes: corbaRepositoryId
 and description.  corbaRepositoryId is a multivalued attribute that
 is used to store the repository ids of the interfaces implemented by
 a CORBA object.  description is used to store a textual description
 of a CORBA object.

Ryan, et al. Informational [Page 2] RFC 2714 Schema for CORBA Object References October 1999

 The corbaObjectReference class has one mandatory attribute: corbaIor.
 corbaIor is used to store the object's stringified IOR.
 corbaIor and corbaRepositoryId are defined in Section 3; description
 is defined in [v3Schema].

3. Attribute Type Definitions

 The following attribute types are defined in this document:
     corbaIor
     corbaRepositoryId

3.1 corbaIor

 This attribute stores the string representation of the interoperable
 object reference (IOR) for a CORBA object. An IOR is an opaque handle
 for the object which contains the information necessary to locate the
 object, even if the object is in another ORB.
 This attribute's syntax is 'IA5 String' and its case is
 insignificant.
 ( 1.3.6.1.4.1.42.2.27.4.1.14
  NAME 'corbaIor'
  DESC 'Stringified interoperable object reference of a CORBA object'
  EQUALITY caseIgnoreIA5Match
  SYNTAX 1.3.6.1.4.1.1466.115.121.1.26
  SINGLE-VALUE
 )

3.2 corbaRepositoryId

 Each CORBA interface has a unique "repository id" (also called "type
 id") that identifies the interface.  A CORBA object has one or more
 repository ids, one for each interface that it implements.
 The format of a repository id can be any string, but the OMG
 specifies four standard formats:
    a. IDL-style
     IDL:Prefix/ModuleName/InterfaceName:VersionNumber

Ryan, et al. Informational [Page 3] RFC 2714 Schema for CORBA Object References October 1999

 For example, the repository id for the "NamingContext" in OMG's COS
 Naming module is:  "IDL:omg.org/CosNaming/NamingContext:1.0".
    b. RMI-style
     RMI:ClassName:HashCode[:SUID]
 This format is used by RMI-IIOP remote objects [RMI-IIOP].
 "ClassName" is the fully qualified name of the class (for example,
 "java.lang.String"). "HashCode" is the object's hash code (that is,
 that obtained by invoking the "hashCode()" method).  "SUID" is the
 "stream unique identifier", which is a 64-bit number that uniquely
 identifies the serialization version of the class; SUID is optional
 in the repository id.
    c. DCE-style
     DCE:UUID
 This format is used for DCE/CORBA interoperability [CORBA-DCE].
 "UUID" represents a DCE UUID.
    d. "local"
 This format is defined by the local Object Request Broker (ORB).
 The corbaRepositoryId attribute is a multivalued attribute; each
 value records a single repository id of an interface implemented by
 the CORBA object.  This attribute need not contain a complete list of
 the interfaces implemented by the CORBA object.
 This attribute's syntax is 'Directory String' and its case is
 significant.  The values of this attribute are encoded using UTF-8.
 Some values may require translation from their native representation
 in order to be correctly encoded using UTF-8.
 ( 1.3.6.1.4.1.42.2.27.4.1.15
  NAME 'corbaRepositoryId'
  DESC 'Repository ids of interfaces implemented by a CORBA object'
  EQUALITY caseExactMatch
  SYNTAX 1.3.6.1.4.1.1466.115.121.1.15
 )

Ryan, et al. Informational [Page 4] RFC 2714 Schema for CORBA Object References October 1999

4. Object Class Definitions

 The following object classes are defined in this document:
     corbaContainer
     corbaObject
     corbaObjectReference

4.1 corbaContainer

 This structural object class represents a container for a CORBA
 object.
 ( 1.3.6.1.4.1.42.2.27.4.2.10
  NAME 'corbaContainer'
  DESC 'Container for a CORBA object'
  SUP top
  STRUCTURAL
  MUST ( cn )
 )

4.2 corbaObject

 This abstract object class is the root class for representing a CORBA
 object.
 ( 1.3.6.1.4.1.42.2.27.4.2.9
  NAME 'corbaObject'
  DESC 'CORBA object representation'
  SUP top
  ABSTRACT
  MAY ( corbaRepositoryId $ description )
 )

4.3 corbaObjectReference

 This auxiliary object class represents a CORBA object reference.  It
 must be mixed in with a structural object class.
 ( 1.3.6.1.4.1.42.2.27.4.2.11
  NAME 'corbaObjectReference'
  DESC 'CORBA interoperable object reference'
  SUP corbaObject
  AUXILIARY
  MUST ( corbaIor )
 )

Ryan, et al. Informational [Page 5] RFC 2714 Schema for CORBA Object References October 1999

5. Security Considerations

 Obtaining a reference to an object and storing it in the directory
 may make a handle to the object available to a wider audience.  This
 may have security implications.

6. Acknowledgements

 We would like to thank Sanjeev Krishnan of Sun Microsystems, Simon
 Nash of IBM, and Jeffrey Spirn of Oracle for their comments and
 suggestions.

7. References

 [CORBA]     The Object Management Group, "Common Object Request
             Broker Architecture Specification 2.2",
             http://www.omg.org
 [CORBA-DCE] Distributed Systems Technology Center and Digital
             Equipment Corporation, "DCE/CORBA Interworking
             Specification", May 1998.
             http://www.omg.org/library/schedule/
             DCE_CORBA_Interworking_RFP.html
 [LDAPv3]    Wahl, M., Howes, T. and S. Kille, "Lightweight Directory
             Access Protocol (v3)", RFC 2251, December 1997.
 [RMI-IIOP]  IBM and Java Software, Sun Microsystems, Inc., "RMI over
             IIOP", June 1999.  http://java.sun.com/products/rmi-
             iiop/index.html
 [v3Schema]  Wahl, M., "A Summary of the X.500(96) User Schema for use
             with LDAPv3", RFC 2256, December 1997.

Ryan, et al. Informational [Page 6] RFC 2714 Schema for CORBA Object References October 1999

8. Authors' Addresses

 Vincent Ryan
 Sun Microsystems, Inc.
 Mail Stop EDUB03
 901 San Antonio Road
 Palo Alto, CA 94303
 USA
 Phone: +353 1 819 9151
 EMail: vincent.ryan@ireland.sun.com
 Rosanna Lee
 Sun Microsystems, Inc.
 Mail Stop UCUP02-206
 901 San Antonio Road
 Palo Alto, CA 94303
 USA
 Phone: +1 408 863 3221
 EMail: rosanna.lee@eng.sun.com
 Scott Seligman
 Sun Microsystems, Inc.
 Mail Stop UCUP02-209
 901 San Antonio Road
 Palo Alto, CA 94303
 USA
 Phone: +1 408 863 3222
 EMail: scott.seligman@eng.sun.com

Ryan, et al. Informational [Page 7] RFC 2714 Schema for CORBA Object References October 1999

9. Appendix - LDAP Schema

  1. - Attribute types –
 ( 1.3.6.1.4.1.42.2.27.4.1.14
  NAME 'corbaIor'
  DESC 'Stringified interoperable object reference of a CORBA object'
  EQUALITY caseIgnoreIA5Match
  SYNTAX 1.3.6.1.4.1.1466.115.121.1.26
  SINGLE-VALUE
 )
 ( 1.3.6.1.4.1.42.2.27.4.1.15
  NAME 'corbaRepositoryId'
  DESC 'Repository ids of interfaces implemented by a CORBA object'
  EQUALITY caseExactMatch
  SYNTAX 1.3.6.1.4.1.1466.115.121.1.15
 )
  1. - from RFC-2256 –
 ( 2.5.4.13
  NAME 'description'
  EQUALITY caseIgnoreMatch
  SUBSTR caseIgnoreSubstringsMatch
  SYNTAX 1.3.6.1.4.1.1466.115.121.1.15{1024}
 )
  1. - Object classes –
 ( 1.3.6.1.4.1.42.2.27.4.2.9
  NAME 'corbaObject'
  DESC 'CORBA object representation'
  SUP top
  ABSTRACT
  MAY ( corbaRepositoryId $ description )
 )
 ( 1.3.6.1.4.1.42.2.27.4.2.10
  NAME 'corbaContainer'
  DESC 'Container for a CORBA object'
  SUP top
  STRUCTURAL
  MUST ( cn )
 )

Ryan, et al. Informational [Page 8] RFC 2714 Schema for CORBA Object References October 1999

 ( 1.3.6.1.4.1.42.2.27.4.2.11
  NAME 'corbaObjectReference'
  DESC 'CORBA interoperable object reference'
  SUP corbaObject
  AUXILIARY
  MUST ( corbaIor )
 )
  1. - Matching rule from ISO X.520 –
 ( 2.5.13.5
  NAME 'caseExactMatch'
  SYNTAX 1.3.6.1.4.1.1466.115.121.1.15
 )

Ryan, et al. Informational [Page 9] RFC 2714 Schema for CORBA Object References October 1999

10. Full Copyright Statement

 Copyright (C) The Internet Society (1999).  All Rights Reserved.
 This document and translations of it may be copied and furnished to
 others, and derivative works that comment on or otherwise explain it
 or assist in its implementation may be prepared, copied, published
 and distributed, in whole or in part, without restriction of any
 kind, provided that the above copyright notice and this paragraph are
 included on all such copies and derivative works.  However, this
 document itself may not be modified in any way, such as by removing
 the copyright notice or references to the Internet Society or other
 Internet organizations, except as needed for the purpose of
 developing Internet standards in which case the procedures for
 copyrights defined in the Internet Standards process must be
 followed, or as required to translate it into languages other than
 English.
 The limited permissions granted above are perpetual and will not be
 revoked by the Internet Society or its successors or assigns.
 This document and the information contained herein is provided on an
 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Ryan, et al. Informational [Page 10]

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