Context
SPARQL (pronounced 'sparkle') is the W3C standard query language for RDF. It is to RDF what SQL is to a relational database, except built natively for graphs. Its strength is at its clearest when crossing the boundaries that other query languages can't.
The cross-silo question is the natural SPARQL question.
Explanation
Compare three questions of increasing complexity:
A question SQL handles well
'Show me all requirements with status Open from the requirements table.' Single-table filter; SQL is fine.
A question SQL handles awkwardly
'Show me all requirements satisfied by components in systems located in seismically active areas.' Three or four joins, possibly across federated databases. Possible, but the SQL gets ugly and the performance is fragile.
A question SQL can't handle naturally
'Walk the dependency tree from this requirement to every component it touches, and report which of those components had design changes in the last six months.' Recursive traversal on a graph. SQL with recursive CTEs gets there, but SPARQL expresses it in three lines.
The point isn't that SPARQL is faster than SQL. It is that the questions you'd ask if asking were easy (questions that span requirements, systems, documents and changes) become naturally expressible. With Weaver, the cross-silo question is the default question.