That's a good question. Both ASN.1 and Google's offering have more limited language coverage (ASN.1 is ancient, but venerable, now in the hands of NCBI), but maybe we should expand that list. These are tools that serialize buffers with razor-sharp binary specifications. I, too, use HDF5 for all of its features, but maybe someone who is rolling their own, for instance, under Spark, should have a solid binary specification.