Larry Masinter wrote: > > I can contribute an application which causes I-M-S dates differing from > > the original modification time. Assume that documents are created on the > > fly by a server/CGI script using multiple other documents or some > > external data. The overall modification time is computed as the latest > > modification time of all parts. > > > If the browser uses this modification time for an I-M-S request and if > > one of the document's parts is fetched using a proxy mechanism the > > original modification time of this part is no longer available. Thus, > > the I-M-S time used in requesting this part may be later than the > > modification time for this part and, refering to the example above, the > > server should return 304, because this part has not changed. > > I'm confused by your example. If the parts are not modified, then they > have the same date as they had the first time. If they ARE modified, > then they have a different date. If you can't tell whether the parts > are modified, then you can't tell the modification time. Without an I-M-S header a requested document is composed out of parts. The modification time for the composed document is computed as the latest modification time of all parts. With an I-M-S header the parts are checked whether they changed since the modification time of the composed document. If one of the parts changed, the document is composed as usual. If not, a 304 response is generated. If one of the parts is fetched from another server using HTTP again, then we would like to use again an I-M-S header to check the part's modification time. We only could use the same I-M-S header as for the composed document because the original modification time of the part is no longer available. So, the I-M-S time is the modification time of the composed document which is equal or *later* to that of the part originally retrieved. In this case we would like to know whether the document changed since exactly *this* time. At *this time* it was apparently not modified as we used it to compose the document. --FranzReceived on Wednesday, 14 February 1996 08:07:03 UTC
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