Technology

Binding and function definition issues

Current CTS approach

The current CTS specification defines the information model using UML and defines the API using the OMG Interface Definition Language (IDL). A sample IDL declaration follows:

     typedef string  OID;
     typedef OID     CodeSystemId;
     typedef string  ConceptCode;
     exception UnexpectedError {
          string possible_cause;
     };
     exception UnknownCodeSystem {
          CodeSystemId codeSystem_id;
     };

     struct ConceptId {
          CodeSystemId codeSystem_id;
          ConceptCode  concept_code;
     };

     boolean isConceptIdValid(
          in ConceptId concept_id,
          in boolean   activeConceptsOnly
     )
     raises (UnknownCodeSystem,
             UnexpectedError);

IDL was chosen because there is a definitive, standard mapping defined between IDL and most programming languages. There are two problems, however. The first is that, while IDL is supposedly technology neutral, the language mappings carry some CORBA related artifacts. The ConceptID declaration above compiles to:

public final class ConceptId implements org.omg.CORBA.portable.IDLEntity
{
  public String codeSystem_id = null;
  public String concept_code = null;

  public ConceptId ()
  {
  } // ctor

  public ConceptId (String _codeSystem_id, String _concept_code)
  {
    codeSystem_id = _codeSystem_id;
    concept_code = _concept_code;
  } // ctor

} // class ConceptId

While the IDLEntity abstract You will note that this standardized mapping is not an interface specification, but rather a concrete class. This It also creates the files:

• ConceptIdHelper.java
• ConceptIdHolder.Java

Both of which contain a lot of CORBA specific information.

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The UnexpectedError exception declaration causes a lot of problems. It generates the Java:

public final class UnexpectedError extends org.omg.CORBA.UserException
{
  public String possible_cause = null;

  public UnexpectedError ()
  {
    super(UnexpectedErrorHelper.id());
  } // ctor

  public UnexpectedError (String _possible_cause)
  {
    super(UnexpectedErrorHelper.id());
    possible_cause = _possible_cause;
  } // ctor


  public UnexpectedError (String $reason, String _possible_cause)
  {
    super(UnexpectedErrorHelper.id() + "  " + $reason);
    possible_cause = _possible_cause;
  } // ctor

} // class UnexpectedError

Which contains references to a CORBA specific UserException as well as UnexpectedErrorHelper references. Both of these are CORBA specific.