22.3.2 Filter syntax and behavior

 As fun as it might be to design and specify a complete language for filtering
resources, that might be getting a bit too far outside the scope of this book. In fact,
there are quite a few language specifications out there that accomplish this goal, such
as Common Expression Language (CEL; https://github.com/google/cel-spec/blob/
master/doc/langdef.md), JSONQuery (https://www.sitepen.com/blog/jsonquery-dataquerying-beyond-jsonpath), RQL (https://github.com/persvr/rql), or Google’s Filtering specification (https://google.aip.dev/160). And in some (but not all) cases it might
even make sense to attempt to rely on the underlying storage system’s querying abilities,
for example enforcing that the query syntax adheres to a specific subset of the equivalent of a SQL WHERE clause, with quite a few restrictions on allowed functionality.