Proposal: Jelly extension for RDF Patch

[Ostrzyciel]

The proposal is to create a non-core extension of Jelly that would implement the RDF Patch protocol for communicating changes to RDF datasets in a transactional manner.

Scope:

• Implement all features of RDF Patch, including transactions and prefixes.
• Some new messages will need to be defined – corresponding to the different commands (e.g., TX, TC, PA, PD...).
  • See also: Proposal: prefix declarations in Jelly-RDF #12
• For the A and D commands, the inner messages should be RDF triples or quads from the core Jelly.
• The outer wrapping messages from Jelly core (RdfStreamRow and RdfStreamFrame) should not be reused/extended, to avoid spaghettifying the code and making changes harder in the future. New wrapping messages dedicated to RDF Patch should be defined.
• Up for discussion:
  • Should the GRAPHS stream type be implemented? It may be problematic... I think just TRIPLES and QUADS will suffice.
  • How should the header look like? Possibly have a new message (PatchStreamOptions) that wraps RdfStreamOptions and adds a new field for the RDF Patch header content?

Implementation:

• Existing related work: RDF Patch implementation with Thrift in Apache Jena
• Create a new .proto file with the format specification.
• Create a separate specification document for Jelly RDF Patch. The spec will use the serialization format spec as its basis in the same way that the gRPC streaming protocol spec does.
• Implement this in Jelly-JVM. Possible module structure (TBD):
  • jelly-patch-core – depends only on jelly-core, library-agnostic implementation
  • jelly-patch-jena – depends on jelly-patch-core and jelly-jena, implementation fully integrated with Apache Jena
  • ... possible implementation for RDF4J, if this will make sense (not sure if there are APIs for this). TBD

Not in scope:

• Integrating Jelly RDF Patch with the gRPC streaming protocol spec. The protocol probably would have to implement something like this. If anyone is interested in that, we can open a separate issue.

Any suggestions, ideas, or expressions of interest are welcome.