Question about XML based conversations

[David]

Hello,

I'm not up to speed on using XML and could use some help.
I get the idea of XML and the various parsers/generators
available. I'm used to the concept of TCP/UDP conversations
and haven't seen this discussed in an XML concept. I've
been asked to put together a medium sized XML interface
to one of my products and need to discuss the ideas with
someone who has worked with this before.

I'll start by asking if all XML Conversations are presumed
to look like simple HTTP Request-Response conversations.

I was aware of this tendancy but when I started to think
about my conversations between my products they don't
usually fit into the simple request-response category.
In several cases the request will really be for a series
of ongoing responses, like monitoring status changes in
a system. I'm also quite used to opening a minimal number
of conversations between computers and queuing multiple
request-response conversations along the same channel.
It seems wasteful to require a new conversation for every
request-response transaction between systems.

Is it possible/useful to open a TCP connection between
machines and then transmit XML messages between the systems?

I've used SAX2 under MSXML to parse a file with multiple
messages and can't figure out how to restart the parser
for the second message.

My current level is just getting up to speed on the basics
of using XML. I'm supposed to design an interface for another
team to use my product that feels XML is best for them. I'd
like to figure out what is reasonable and normal before inventing
methods that they will not want to handle.

I'd also welcome any reading material on the subject, I've
searched www.xml.org/.com and lots of other places and haven't
found the magic keywords that get me to a description for solving
the type of problem I'm trying to solve.

Thank you for your help,

David

 

[Andy Dingley]

I'll start by asking if all XML Conversations are presumed
to look like simple HTTP Request-Response conversations.

I've never heard of "XML Conversations". If you're capitalising this,
is it a proprietary technology ?

It sounds like you're re-inventing SOAP here, which is one part of the
big web-services picture. It's not an "XML topic", because XML is
deliberately a very small-scope protocol and things additional to it
like this are described separately. However your basic idea is right;
XML documents fly about by HTTP. It isn't always HTTP, and sometimes
it might not even be XML, but that's the mainstream.

 

[David]

I've never heard of "XML Conversations". If you're capitalising this,
is it a proprietary technology ?

It sounds like you're re-inventing SOAP here, which is one part of the
big web-services picture. It's not an "XML topic", because XML is
deliberately a very small-scope protocol and things additional to it
like this are described separately. However your basic idea is right;
XML documents fly about by HTTP. It isn't always HTTP, and sometimes
it might not even be XML, but that's the mainstream.

Thanks Andy.

I've read about XML for years and seen various uses. One used XML
requests in files that were later replaced by XML responses in
similarly named files. I've never, ever seen it mentioned that XML
is generally for use over an HTTP conversation, though I'm aware
that is where it is used most. I'd also not considered that everything
was required to be request-response and stateless by most uses of
XML encoding.

David

 

[Jesse Hager]

Hi David,

One thing you might want to check out is the Jabber/XMPP protocol, this
is an open instant messaging protocol that uses continuous streams of
XML elements for communication. Several people have used it as the
transport protocol for other projects. It may give you some ideas on
how to implement a non request-response protocol. Or maybe just grab
one of the existing XMPP libraries and use it to send your own XML data

The main Jabber Site:
http://www.jabber.org

The core XMPP protocol spec (see the XML Streams section 4):
http://www.jabber.org/ietf/draft-ietf-xmpp-core-23.txt

The instant messaging part is here:
http://www.jabber.org/ietf/draft-ietf-xmpp-im-22.txt

Hope this helps.

 

[David]

Hi David,

One thing you might want to check out is the Jabber/XMPP protocol, this
is an open instant messaging protocol that uses continuous streams of
XML elements for communication. Several people have used it as the
transport protocol for other projects. It may give you some ideas on
how to implement a non request-response protocol. Or maybe just grab
one of the existing XMPP libraries and use it to send your own XML data

The main Jabber Site:
http://www.jabber.org

The core XMPP protocol spec (see the XML Streams section 4):
http://www.jabber.org/ietf/draft-ietf-xmpp-core-23.txt

The instant messaging part is here:
http://www.jabber.org/ietf/draft-ietf-xmpp-im-22.txt

Hope this helps.

Thanks Jesse. That sounds like what I was thinking of.