VIATRA/DeveloperDocumentation/Viatra2.0Brainstorming

Viatra 2.0 Design Docs and Brainstorming, Fall 2017

Minimum dependencies

Components to keep or graduate:

Main points to address

Scoping and imports in VQL (breaking backward compatibility on query definitions)
Minimum dependency updates (see above)
Remove all deprecated API
Consider using runtime exceptions instead of checked exceptions
See list of issues in 2.0.0M1

Top priority until March 2018

Add file-level element that can receive annotations
Rethink public/private patterns
- Let runtime know what is important for `Release` performance
- Important for incremental engines: know what must be maintained, what can be flattened
Compositional sources of base relations (scopes)
- Better support for non-EMF scopes
- Better support for user-supplied relations, magic sets, traceability, etc.
- Must be mixable as freely as possible
Minor syntactic sugar
- graph-like mnemonic for unary and binary base relations
- neg {local pattern}
- neg BareType(notWrappedInHelperPattern)

API debt
- Remove all deprecated API
- Consider using runtime exceptions instead of checked exceptions
Compositional scopes to support associated language goal
User-supplied relations
- VQ Engine owner shall be able to provide (through an easy API) the contents of custom relations that the query definitions can rely on
  - API1 to provide custom relations that realize the relevant IQMC, IQRC methods, including index lookup and notifications
  - API2 where index lookups are taken care of, contents and notifications are still provided by the user
  - API3 where these relations are implemented e.g. as a set (with indexer lookups, notifications, etc.), the user can call manipulation operations
- Must be possible to add a posteriori to any other scope (e.g. EMF), see also compositional scopes
Do we need surrogate values in the EMF base index?
Rethink matcher API
- In case of surrogates, remove types from API
- Can Matches also be Tuples, or at least backed by them? Try to reduce (persistent and transient) duplication.
Distributed processing extensions
- ???