Aristotle Pagaltzis wrote:
> I wonder how you would make sure that the document is
> well-formed. Since the stream never actually ends and there
> is no way for a client to signal an intent to close the connection,
> the <feed> at the top would never actually be accompanied by a
> </feed> at the bottom.
This is a problem which has become well understood in the use and
implementation of the XMPP/Jabber protocols which are based on streaming
XML. Basically, what you do is consider the open tag to have a virtual
closure and use it primarily as a carrier of stream metadata. In XMPP
terminology, your code works at picking "stanzas" out of the stream that can
be parsed successfully or unsuccessfully on their own. In an Atom stream,
the processor would consider each atom:entry to be a parseable atomic unit.
> If you accept that the stream can never be a complete
> well-formed document, is there any reason not to simply send a
> stream of concatenated Atom Entry Documents?
> That would seem like the absolute simplest solution.
You could certainly do that, however, you will inevitably want to
pass across some stream oriented metadata and you'll eventually realize that
much of it is stuff that you can map into an Atom Feed. (i.e. "created
date", unique stream id, stream title, etc.). Since we're all in the process
of learning how to deal with atom:feed elements anyway, why not just reuse
what we've got instead of inventing something new.
A rather nice side effect of forming the stream as an atom feed is
the simple fact that a "log" of the stream can be written to disk as a
well-formed Atom file. Thus, the same tools that you usually use to parse
Atom files can be used to parse the log of the stream. It is nice to be able
to reuse tools in this way... (Note: At PubSub, the atom files that we serve
to people are, in essence, just slightly stripped logs of the proto-"Atom
over XMPP" streams that they would have received if they had been listening
with that protocol. In our clients we can use the same parser for the stream
as we do for atom files. It works out nicely and elegantly.)
bob wyman
