Hello Oliver,
Thanks for your special interest in XRPC!
On Sun, Feb 25, 2007 at 05:32:50PM +0100, oliver oli wrote:
> Hello,
>
> good to know that it would be possible.
>
> I just wonder why the protocol is so overly complicated.
You might need some time to get used to the protocol, but it is not
extremely complicated. It might help if you keep this pattern in mind:
call -> sequence -> sequence-item
We have chosen this protocol, because we want to support the following
features:
1. Loop-lifted RPC calls, ie. all RPC calls in a for-loop to the same
destination are wrapped in *one* request message. Hence, we need a
<call> tag to separate each iteration. This is the most important
feature of XRPC.
2. Since a function can have multiple parameters, needless to say, we
need something to separate the parameters, that is the <sequence>
tag. We chose the name "sequence" because every value can be a
sequence in XQuery.
3. We want to have full support of the XQuery language, which means that
it should be possible to call functions that have sequence
parameters. Thus we separate each item in a sequence with its type
as tag name. This way, we also preserve the type information.
If you have suggestions to improve the protocol, I will be very glad to
hear!
> For simple queries the overhead seems huge.
I agree that for simple queries, the space taken by the overhead can be
larger than the space used to carry the parameters. But I'm actually
not worried about this, because I think this phenomenon is common to all
network protocols. The overhead is about 500Bytes, plus the overhead of
a conventional HTTP header, there is still some place left for the
parameters of simple queries, so that all these things will fit in one
packet.
> Would it be possible to use a RESTful style for xrpc?
Currently, the only item on the agenda, that is REST-style-alike, is
retrieving an XML document stored in the DB using a special URL. For
example, the following URL returns you "hello.xml" which has been
shredded into your MonetDB/XQuery DB earlier:
http://your.xrpcserver.host/xrpc/hello.xml
The '/xrpc' redirect the request to a special handler which retrieves
the document from the DB instead of from the FS.
(Full) support of REST style at the server side will not be a short term
issue. But I think a REST style request can be easily implemented at
the client side, for example, by using JavaScript. It should be easy
for JavaScript to trap the following request:
http://your.xrpcserver.host/xrpc/person.xml/name
and generate the desired XRPC request message.
Regards,
Jennie
>
> Ying Zhang wrote:
> > Hello Oliver,
> >
> > Thanks for your interesting in MonetDB/XQuery!
> >
> > I think it would be possible to use XRPC as an alternative of Mapi. The
> > only restriction is that built-in and in-line functions are not
> > supported. The work around is just declaring those functions in an
> > XQuery module.
> >
> > Regards,
> >
> > Jennie
>
>
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