Ion readers should return symbol zero for all local symbols with unknown text.

[tgregg]

See http://amzn.github.io/ion-docs/guides/symbols-guide.html for more information.

[toddjonker]

This issue needs more careful statement of intent; as stated it is inappropriate behavior.

To the point, there’s a big difference between out-of-range SID and unknown symbol text.

[tgregg]

This issue has nothing to do with out-of-range SIDs. It is only concerned with symbol IDs with unknown text that occur between the local symbol table's min_local_id and max_id.