DDS-XTypes 1.2 RTF Avatar
  1. OMG Issue

DDSXTY12 — Consider expanding TypeId 16 octets rather than 8

  • Key: DDSXTY12-127
  • Status: closed  
  • Source: Real-Time Innovations ( Gerardo Pardo-Castellote)
  • Summary:

    Currently the TypeId is 8 octets.
    The TypeId distinguishes identifies a Type and needs to have a low probability of collision relative to the size of the set (collection of types) that can potentially apply to the scope.

    A hash of 64 bits provides reasonably low probability of collision (e.g. < 1 in 10 million) when the set of possible values has a size smaller than 2 million. This was more than enough when we consider the "collection of types" to just be the types that can be associated with a particular Topic on a particular Domain.

    However if we consider the problem of identifying Types across Topics within a Domain, or across domains, or even across applications that evolve over time (e.g. keep a database of TypeId that is built over time) then 64 bits may not be enough...

    We should consider whether to make it 16 bytes now. If these use cases can become important then now would be the time to make the change...

  • Reported: DDS-XTypes 1.1 — Wed, 28 Sep 2016 22:13 GMT
  • Disposition: Duplicate or Merged — DDS-XTypes 1.2
  • Disposition Summary:

    The size of the TypeID is being increased so hashes are 14 bytes.

    This issue is being merged with DDSXTY12-100 because the resolution of that issue is already increasing the sizes of the hashes in the TypeID to 14 bytes.

  • Updated: Thu, 22 Jun 2017 16:42 GMT