[Fiware-middleware] DFKI Thrift-based IDL Proposal

[Dmitri Rubinstein]

No, our starting point is Thrift IDL, and I describe all differences 
including a justification. Task with OMG IDL as foundation is eProsima's 
task, since they are experts in OMG IDL.

https://docs.google.com/document/d/1a0pttnIaHX6aGvCqvostEm8iB1n1hHD7vg7JxbfNe5Y/edit:

Deadline Thu EOB
   Joined document that describes the new IDL
   Features that have been dropped out of OMG (ePros)
     Including a justification
   Features that are proposed by Thrift (DFKI)
     Including a justification
     In particular related to features that are required by KIARA 
innovations

Best,

Dmitri

On 10/21/14 14:16, Thomas Michael Bohnert wrote:
> Dimitry,
>
> Thanks - just one question. Is this starting from the OMG IDL as
> foundation?
>
> I assume so since this was the task to complete.
>
> Best - Thomas
>
> On 10/21/2014 02:13 PM, Dmitri Rubinstein wrote:
>> Hi all,
>>
>> as discussed in the last meeting I put here information about our IDL
>> proposal. When final document appears online I will copy this text to it.
>>
>> 1. KIARA/DFKI IDL is based on Apache Thrift IDL, with the grammar
>> available here:
>>
>> https://thrift.apache.org/docs/idl
>>
>> Our grammar is available here:
>>
>> https://forge.fi-ware.org/plugins/mediawiki/wiki/fi-ware-private/index.php/Middleware_-_KIARA_-_User_and_Programmers_Guide#KIARA_Interface_definition_language
>>
>>
>> Note: our goal was not to keep a full backwards compatibility with
>> Thrift, but to modify a grammar only when necessary. Still technically
>> we can be backwards compatible (we can parse already *existing* Thrift
>> IDL files), since we avoided to remove any functionality from Thrift
>> (only 'oneway' keyword was removed, see below). However, this was not
>> tested yet.
>>
>> 2. We did following modifications:
>>
>> 2.1 Base types
>>
>> 2.1.1 Added unsigned types missing in Thrift: u8, u16, u32, u64
>>
>> 2.1.2 Renamed bool to boolean, byte to i8 (signed byte).
>>
>> 'boolean' is used more frequently than 'bool' in other IDLs. We can
>> switch back to 'bool' if desired.
>>
>> 'byte' as a signed integer is not consistent with names of other signed
>> integers (i16, i32, i64). We can switch back to 'byte' as signed 8-bit
>> integer and use 'ubyte' as unsigned 8-bit integer if desired.
>>
>> A comparison table for basic types for DFKI/KIARA, CORBA, Thrift, etc.
>> is here:
>>
>> https://forge.fi-ware.org/plugins/mediawiki/wiki/fi-ware-private/index.php/Middleware_-_KIARA_-_User_and_Programmers_Guide#Primitive_types
>>
>>
>> 2.2 Annotations
>>
>> The official Thirft grammar available on the web (see link above) *does
>> not* contain flexible annotation syntax. There is an annotation support
>> available in the latest Thrift version:
>>
>> https://github.com/apache/thrift/blob/master/test/AnnotationTest.thrift
>>
>> However, annotations are limited to key-value pairs and even more
>> important: seems that function arguments and return types can't be
>> annotated, there are at least no examples.
>>
>> Instead of using Thrift annotations we decided to introduce a different
>> syntax inspired by WebIDL:
>> http://www.w3.org/TR/WebIDL/#idl-extended-attributes.
>>
>> 2.2.1 Added syntax for defining custom annotations, similar to structs
>> and exceptions:
>>
>> annotation HTTPPort {
>>     i32 port = 80
>> }
>>
>> 2.2.2 Added ability to annotate following entities: services, service
>> functions, return types of service functions, arguments of service
>> functions. We need this especially for security-related features. For
>> example:
>>
>> namespace * enc
>>
>> // HTTPPort annotates the 'enc' service with argument 8080
>> [HTTPPort(8080)]
>> service enc {
>>
>>       // Function ping is annotated with Oneway and Encrypted annotations
>>       // without parameters
>>       [Oneway, Encrypted]
>>       void ping()
>>
>>       // In function saveString Argument s of type string
>>       // is annotated with annotation OptionallyEncrypted without
>>       // parameters
>>       void saveString(string fileName, [OptionallyEncrypted] string s)
>>
>>       // Return type of function loadString is annotated with
>>       // annotation OptionallyEncrypted without parameters
>>       string [OptionallyEncrypted] loadString(string fileName)
>> }
>>
>> Also see our documentation:
>> https://forge.fi-ware.org/plugins/mediawiki/wiki/fi-ware-private/index.php/Middleware_-_KIARA_-_User_and_Programmers_Guide#Functions_2
>>
>>
>> 2.3 Generic types
>>
>> Original Thrift IDL supports following predefined container types:
>> list<T>, map<T1,T2>, and set<T>. We decided to extend this syntax to
>> arbitrary generic types: GenericType<T1, T2, ..., Tn> where Ti can be
>> either type or constant. In this way we can support types like bounded
>> arrays but still keep backwards compatibility with the original syntax:
>>
>> array< i32, 2> // bounded array of size 2
>> array< i32, array< i32, 4> > // two-dimensional array
>>
>> 2.4 Removed Thrift features
>>
>> We removed 'oneway' keyword from Thrift because we can use annotation
>> Oneway:
>>
>> Original Thrift:
>>
>> service Test {
>>     oneway void zip()
>> }
>>
>> Our grammar:
>>
>> service Test {
>>     [Oneway] void ping()
>> }
>>
>> If backwards-compatibility to Thrift is desired we can try to support
>> both styles.
>>
>> 2.5 Unused Thrift features
>>
>> We currently parse but ignore following Thrift features that are missing
>> in OMG IDL:
>>
>> Struct fields can have optional integer identifier.
>> Struct fields can be 'required' or 'optional'.
>>
>> 2.6 Planned extensions
>>
>> Thrift does not provide entity like CORBA's 'module'. The namespace
>> keyword used by Thrift only allow to specify namespace in the generated
>> code. We plan to add module NAME { ... } entity in order to provide
>> support for nested IDL namespaces as well as annotations per module.
>>
>> Best,
>>
>> Dmitri
>> _______________________________________________
>> Fiware-middleware mailing list
>> Fiware-middleware at lists.fi-ware.org
>> https://lists.fi-ware.org/listinfo/fiware-middleware
>>