Object Interconnections Using the Portable Object Adapter for Transient and Persistent CORBA Objects

In this column, we continue our presentation of the new OMG Portable Object Adapter (POA) [1]. The POA was adopted by the OMG in mid-1997 as a replacement for the Basic Object Adapter (BOA), which was the original CORBA object adapter. As we described in our last column, the BOA was a major source of portability problems for CORBA applications due to its imprecise specification. Serious users of CORBA can attest to the frustrations of porting applications across multiple ORBs. Rather than trying to repair the BOA, which would have required all CORBA applications written to the original specification to change, the OMG opted to create a whole new object adapter. This Portable Object Adapter (POA) specification is much more precise in its use of terminology than the old BOA specification. Thus, our last column was devoted almost entirely to explaining not only object adapters in general, but the POA terminology as well. Our next several columns will examine detailed examples of how the POA can be used by real-world CORBA C++ applications. The POA specification is rather daunting, so we can’t cover all the features and use-cases in a single column. Therefore, we’ll start by explaining the usage of several POA policies described in our previous column [2]. Our primary focus in this column will be on the POA features that support transient and persistent CORBA objects. Subsequent columns will explore other POA features and discuss the circumstances under which various features are best used.