Persistent Application Systems (PASs) are of increasing social and economic importance. They have the potential to be long-lived, concurrently accessed and consist of large bodies of data and programs. Typical examples of PASs are CAD/CAM systems, office automation, CASE tools, software engineering environments and patient-care support systems in hospitals. Orthogonally persistent object systems are intended to provide improved support for the design, construction, maintenance and operation of PASs. The persistence abstraction allows the creation and manipulation of data in a manner that is independent of its lifetime thereby integrating the database view of information with the programming language view. This yields a number of advantages in terms of orthogonal design and programmer productivity which are beneficial for PASs. Design principles have been proposed for persistent systems. By following these principles, languages that provide persistence as a basic abstract...

In this paper, the authors share their experiences gathered during the design and implementation of the CORBA Persistent Object Service. There are two problems related to a design and implementation of the Persistence Service: first, OMG intentionally leaves the functionality core of the Persistence Service unspecified; second, OMG encourages reuse of other Object Services without being specific enough in this respect. The paper identifies the key design issues implied both by the intentional lack of OMG specification and the limits of the implementation environment characteristics. At the same time, the paper discusses the benefits and drawbacks of reusing other Object Services, particularly the Relationship and Externalization Services, to support the Persistence Service.

This report is a study of three of the CORBA object services. Based mainly upon [OMG 92, OMG94a, OMG94b], the study aims to identify the main issues of the design and implementation architecture of the persistent, events, and replication object services. The reseach was done with an emphasis upon employing the services in a halfbridge and gateway CORBA implementation which are the main goals of the TOCOOS project.

INTRODUCTION .................................................................................................................................................3 2. ORBS ADAPTATION TO INTERORB_PROXY REQUIREMENTS ...............................................................3 2.1 INTERORB_PROXY REQUIREMENTS.........................................................................................................................3 2.1.1 ORB interface ................................................................................................................................................3 2.1.2 Dynamic Invocation Interface ........................................................................................................................4 2.1.3 Dynamic Skeleton Interface ..............................................................................

The CORBA specification proposes a collection of Object Services that CORBA objects may use to enhance their functionality. In this paper, the authors share their experience gathered during the design and implementation of the Persistent Service as a part of the TOCOOS project. Moreover, the paper discusses benefits and drawbacks of reusing other Object Services, particularly Replication and Externalization, to support the Persistent Service. As the inter-dependencies among the three Object Services are rather complex and potentially circular, the paper aims at providing the reader with an analysis resulting in a set of guidelines a designer or a user of these services can benefit from when resolving inherent trade-offs.