Structure inheritance is described by rules (45) and (48), page 27. The constraints on using forward-declared structures are given in section 7.4.1.4.4.4.4, page 40. For clarity, it would be better if this section made explicit the prohibited uses of forward declarations. This is done for value types in section 7.4.5.4.2 on page 57, "It is illegal to inherit from from a forward-declared value type not previously defined". Though this is a clarification it has been shown to be needed as this illegal use for forward-declared structures has occurred in external (to OMG) specifications that use IDL.

The section Imports contains

The effects of an import statement are as follows:

• [...]
• Importing a name scope recursively imports all name scopes nested within it.

This looks counter intuitive to me.

Example:

module commontypes {
   module nested1 {
      enum RGBColor { RED, GREEN, BLUE };
   }
   module nested2 {
      enum TrafficLight { READ, YELLOW, GREEN };
   }
};

What happens if another module does "import commontypes"?

If, as the standard says, all name scopes nested within "commontypes" are recursively imported then this would lead to errors:
The enum values RED and GREEN would be directly visible and would be in conflict with each other.

7.4.15.4.2 on p.101 contains the rule

(225) <annotation_appl> ::= "@" <scoped_name> [ "(" <annotation_appl_params> ")" ]

The nature of the EBNF notation leaves room for interpreting that between the @ and the <scoped_name> there could appear spaces, tabs, or even comments.

On the other hand, 7.4.15.4.1 on p.100 contains:

(220) <annotation_header> ::= "@annotation" <identifier>

Here, it is clear that @annotation shall be treated as a single token without intermittent characters between @ and annotation.

I propose adding a clarification in the explanations at the beginning of p.102 (following rule 227):

Applying an annotation consists in prefixing the element under annotation with:

• The annotation name ( <scoped_name> ) prefixed with the at symbol( @ ), also known as commercial at. There shall be no intermittent spaces, tabs, or comments between @ and <scoped_name>.

The last sentence is my proposed addition.

Programming languages that have the concept of modules/namespaces also include the concept of "using" a namespace type such that one can ommit the explicit reference to the 'used' namespace.

The following is an example for C++:

Assume the declaration:

namespace MyNamespace
{
    class MyClass
    {
    public:
        void my_operation() {}
    };
    void MyFunction1(MyClass) {}
}

Normally these types need to be accessed using their fully qualified names:

MyNamespace::MyClass obj;
obj.my_operation();
MyNamespace::MyFunction1(obj);

This can be cumbersome when having to reference a lot of types in the same namespace, specially for deep nested namespaces.

The C++ using declaration can bring the name space or individual types into scope simplifying the coding as in:

using MyNamespace::MyClass;
MyClass obj;
obj.my_operation();
MyFunction1(obj);

Or alternatively bringing every type in the name space into the scope:

using namespace MyNamespace;
MyClass obj;
obj.my_operation();
MyFunction1(obj);

Java and C# provide similar facilities:
In Java the "import" keyword is used to import packages or types into the scope. The syntax is:

import package.name.ClassName;   // To import a certain class only
import package.name.*;

In C# the "using" keyword is used to import namespaces or types into the scope. The syntax is:

using  MyNamespaceName.MyClassName;   // To import a certain class only
using MyNamespaceName;

This issue request that a similar facility is added to IDL

Table 7-13 (Integer types) should have a little bit wider column 1 and the font size "See Building Block Extended Data" should match the other font in this table

In section 7.4.4.4.2 it is explained that an annotation may be used in a shortened form in the following conditions:

• There is no member or only one member with a default value.
  • In that it is allowed to apply the annotation by using just the annotation name.
• There is only one member.
  • In that case you may apply the name of the annotation and the value of its member, without explicitly mentioning the member name and the equals sign.

However, the second bullet may break backward compatibility when annotations get extended with additional members in future spec releases. Consider the following example:

@bit_bound(32)
bitmask DataRepresentationMask {
   @position(0) XCDR, 
   @position(1) XML,
   @posiiton(2) XCDR2
}

@annotation data_representation {
    DataRepresentationKind allowed_kinds;
};

Now to annotate an IDL type to support only the XCDR2 annotation, I can apply a shortened annotation like this:

@data_representation(XCDR | XCDR2)
struct Foo {
   long my_long;
};

Now suppose in a future version of the spec, we extend the @data_representation annotation with an additional field to specify the supported endianness, like this:

enum EndiannessKind {
    BIG_ENDIAN,
    LITTLE_ENDIAN,
    NATIVE_PLATFORM
};

@annotation data_representation {
    DataRepresentationKind allowed_kinds;
    EndiannessKind endianness;
};

In this case, the addition of the new member suddenly invalidates existing IDL files that use the shorthand notation.

What I want to propose is to allow the shorthand notation to be used for implicitly referring to the first available member. That is fully compatible with the current rule, but will also still apply when new members are added afterwards.

Extend the grammar for Constants to allow constants for all Core Data Types that are currently not allowed:

• sequence
• structure
• union
• array

There is a general need to document the IDL. However the IDL language does not provide any standard way to do this. As a consequence people may be forced to define custom annotations which would preclude the use across projects and/or development of general tools that are documentation aware.

To remediate this the suggestion is to add some built-in annotations that maybe used to document the IDL. For example the @documentation annotation below:

@annotation documentation {
    string value default "TBD";
};

This annotation could applied to a type declaration or to a member / element, as in:

@documentation("This documents the type Foo")
struct Foo {
    @documentation("documentation for member m1")
    long m1;
    @documentation("documentation for member m2")
    long m2;
 };

@documentation("This documents the type MyEnum")
enum MyEnum {
    @documentation("documentation for literal L1")
    L1,

    @documentation("documentation for literal L2")
    L2
 };

The example for 'References to a Template Module' contains the line:
alias MyTemplModule2<S1, S2, m> MyTemplModule;

According to rule 193, 'MyTemplModule2' should be a scoped_name that refers to a previously defined Template Module. There is nothing else (successfully) defined as 'MyTemplModule2'. I think this line should be:

alias MyTemplModule<S1, S2, m> MyTemplModule2;

IDL 4.0 contained specific grammar rules for where annotations can be applied. Issue IDL41-9 revised these rules and left the spec with the general statement that (7.4.15.4.2): "An annotation may be applied to any IDL constructs or sub-constructs."

This is problematic for the following reasons:

• The phrase "under annotation" is used in multiple places in the spec without it being defined
• Tool implementors using a grammar based on the one in the spec need to make their own enhanced grammar to include <annotation_appl>, which undermines the usefulness of having a grammar in the spec
• Documentation of specific annotations (whether standardized in IDL, standardized in other OMG documents such as XTYPES, or non-standard) has no systemic way of describing where the annotation should be used
• Users have little assurance that their IDL will be understood by all conforming tools, even when using standardized annotations

This was originally reported as https://issues.omg.org/browse/CORBA34-1

In 7.5.1, the 3rd bullet point lists "interface, struct, union, exception." Instead the same language from 7.5.2 ("The following kinds of definitions...") should be in effect.

8.3.3.1 "@default" and 8.3.6.2 "@oneway" specify standardized annotations that a user is not allowed to make use of because grammar rule 225 (in 7.4.15.4.2) states that a <scoped_name> is used to identify the applied annotation. From rule 4, a <scoped_name> is built out of <identifiers> which can't be keywords (see 7.2.1, 7.2.3, 7.2.4).

The grammar rule 195 (for struct_def) indicates that a structure may either inherit from a base or may be empty, but not both. The intent based on the text around the rule seems to be to allow structs that are both empty and inheriting.

IDL 4.2 syntax supports inheritance of only interfaces, valuetypes, and structures.

There are multiple scenarios where it would be useful to inherit other types, specifically Unions and Enumerations.

(1) Inheritance of unions

This would be very useful in some specs where unions are automatically generated. For example unions are created interface definitions in DDS-RPC and derived interfaces would like to use unions that "inherit" the unions in the base interfaces.

This would be useful when a "derived" union wants to add some more cases to the base union.

The derived union would have to use the same discriminator type. All it can do is add new discriminator cases that do not conflict with the non-default discriminator in the base union.

It can add a default case if not present in the base union.

Proposed syntax would be:

union DerivedUnion : BaseUnion {
    case 1 :
       Case1Type case1meber;
...
};

(2) Inheritance of enumerations

This is useful to add literals to an existing enumeration without touching the original definition.

The literals on the derived union would be constrained to not conflict the literals in the base class.

Proposed syntax would be:

enum DerivedEnum : BaseEnum {
    AdditionalLiteral1,
    ...
};

The 'Group of Annotations General Purpose' includes the @autoid annotations which can optionally specify a HASH as in @autoid(HASH).

To be useful this must be augmented with the @hashid("MyString") annotation that allows an ID to be explicitly assigned by computing the hash of a string using the same algorithm that @autoid(HASH) uses.

Section 7.4.11.4.3 on page 85 contains:

(181) <connector_inherit_spec> ::= ":" <scoped_name>

The rule number should be 182.

Page 112 top continues the bullet list started on p.111 bottom:

• May precise on which elements the annotation is valid in that specific context. That list may be only a subset of all the possible ones.

Replace "precise" by a verb, e.g. specify, detail, elaborate, or expound.

• Shall indicate the default behavior [...]. This is because the later values are intended to be the most logical values when the annotation is present.

"later" -> latter

In section 7.4.11.4.3 page 87 and in Annex A page 132, <connector_inherit_spec> should have the rule number 182.

7.2.6.2.1 on page 23 contains:

A character literal is one or more characters enclosed in single quotes, as in:
const char C1 = ’X’;

Please use the ASCII apostrophe:
const char C1 = 'X';

If an implementation wishes to claim support for the "Building Block Extended Data-Types", it must support all of its complements, including the section 7.4.13.4.4 "Integers restricted to holding 8-bits of information".

However, if the targeted programming language does not natively support int8 or uint8 then it is not obvious how the "unsupported" type may be mapped.

For example, the Java language has a native type byte which is signed.
The question then arises how the implementation maps the type uint8.

The implementation could choose to

• Maintain bit size:
  In that case, it would map uint8 to Java byte.
  The question then arises how values exceeding the positive signed maximum (127) are handled.
• Maintain numeric range:
  In that case, it could map uint8 e.g. to Java short (16 bit quantity) or int (32 bit quantity).
  The implementation must then address the interoperability with other languages where uint8 is
  mapped to an 8 bit quantity.
• Use yet a different mapping, for example a holder class (cf. Short, Integer, etc.)

I therefore propose adding the requirement that the implementation shall document its mapping choice:

If the targeted programming language does not natively support int8 or uint8 then an implementation
shall include information about how it maps the types which lack the native language support.

This is not an issue in the strict sense, just a usability observation.
If I copy/paste the word <porttype_def> of rule 174, it comes out as

>‎ yedeepyotrop <

In section 4 "Terms and Definitions" on page 7, the last sentence is:

> [...] Building blocks are described in
> clause 0,

The sentence seems to end on the comma; furthermore, I cannot find a "clause 0".

There is a stray > at the end of the title,

7.4.1.4.1 IDL Specification>

Page 133 last item of "From Building Block Extended Data-Types" :

(1) <unsigned_longlong_int> ::+ “uint64”

The rule number should be 215.

As an aside, the quotation marks used in rules 208 to 215 are fancy Unicode characters while the rest of the grammar uses the regular ASCII code 34 decimal.

The title of 7.4.13.4 says:

7.4.13.4 <unsigned_longlong_int> ::+ “uint64”Explanations and Semantics

This is a formatting error. The {{ <unsigned_longlong_int> ::+ “uint64”}} should appear before the title as one of the rules following:

(214) <unsigned_long_int> ::+ “uint32”

Note that this problem appears only in the generated PDF. The word document is fine.

Section 7.4.1.4.4.4.3 Enumerations says:

An enumeration must contain at least one enumerator and no more than 232.

The 232 is a typo. It was meant to be 2 ³²

7.4.13.4 "Explanations and Semantics" gives a synoptic list of the complements,

Those complements are:

• Additions to structure definition in order to support single inheritance and void content (no members).
• Ability to discriminate a union with other types (wide char and octet).
• An additional template type (maps).
• Additional constructed types (bitsets and bitmasks).

The complement "Integers restricted to holding 8 bits of information" (7.4.13.4.4) should be added there.