On Sun, Jul 8, 2012 at 6:52 AM, Aharon (Vladimir) Lanin <aharon@google.com>wrote: > 1. Make isolates weaker than embeddings/overrides, i.e. ignore a PDI when > a PDF is expected, and have a PDF close all isolates opened between it and > its marching LRE/RLE/LRO/RLO. Thus, in a, the PDI is ignored, and in b, the > PDF ends the scope of the RLI as well as the LRE. > > 2. Vice-versa - make isolates stronger than embeddings/overrides, i.e. > ignore a PDF when a PDI is expected, and have a PDI close all > embeddings/overrides opened between it and its marching FSI/LRI/RLI. > Thus, in a, the PDI ends the scope of the RLE as well as the LRI, and in b, > the PDF is ignored. > > Possibility 2 offers greater forward compatibility, since new and old apps > will interpret the PDFs as closing the same scopes when isolates are not > properly nested with respect to embeddings/overrides. > > Possibility 1, on the other hand, gives isolates the desirable feature of > isolating their surroundings from their contents - even when their contents > contains extra or missing PDFs. > > I have decided to go with possibility 2, since IMO > forward compatibility is not very important for what are, essentially, > broken documents. > I don't understand your logic. You say option 2 offers greater forward compatibility, but then say you are choosing 2 because forward compatibility is NOT important. I think backward compatibility is more desirable, i.e., a system that knows nothing of isolates should work without modification, and yet option 2 requires PDI to close an embedding/override, which would violate that goal. You should choose option 1 (PDI weaker than PDF).
Received on Monday, 9 July 2012 05:48:04 UTC