Network Working Group V. Ryan

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.

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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.

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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

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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
)

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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 )
)

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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.

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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: [email protected]

Rosanna Lee
Sun Microsystems, Inc.
Mail Stop UCUP02-206
901 San Antonio Road
Palo Alto, CA 94303
USA

Phone: +1 408 863 3221
EMail: [email protected]

Scott Seligman
Sun Microsystems, Inc.
Mail Stop UCUP02-209
901 San Antonio Road
Palo Alto, CA 94303
USA

Phone: +1 408 863 3222
EMail: [email protected]

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RFC 2714 Schema for CORBA Object References October 1999

9. Appendix - LDAP Schema

-- 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
)

-- 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}
)

-- 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 )
)

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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 )
)

-- Matching rule from ISO X.520 --

( 2.5.13.5
NAME 'caseExactMatch'
SYNTAX 1.3.6.1.4.1.1466.115.121.1.15
)

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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.

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