EntityTag

An HTTP entity tag (ETag) and its strength (RFC 7232 §2.3).

The value is the opaque validator with its surrounding quotes stripped; weak is true for a weak validator (the header carried the W/ prefix). The distinction matters for conditional writes: If-Match uses the strong comparison function, so a weak validator can never satisfy it — sending a weak tag as If-Match guarantees a 412. Some Solid servers (notably Node Solid Server / solidcommunity.net) only ever emit weak ETags for RDF resources, which is why the library falls back to If-Unmodified-Since for those writes rather than sending a validator that is doomed to fail.