I am a fan of context and by having one for *all*
interactions, we can promote more of the stateless services. Here are
some of my thoughts on context:
Yes, it would be good if we could make progress on the context format.
The basic structure could pass common features (such as the coordinator
reference, timeout etc) in a strongly types fashion, and we can then allow
model specific data in a less strongly typed manner (e.g., a CORBA any in the
example), because any user of that data must check the type structure of the
context anyway.
1. Context could be viewed as a set
of attribute assertions, some of them signed and even
encrypted.
Agreed. There's nothing to say that the model specific data couldn't be
encrypted, for example.
2. Context is information other than
the actual transaction data and can include the user credentials, any
previous state, time of day, geographic location of the calling entity,
...
I think that the general context should be a series of specific context
instances, one for transactions (which only talks about transaction related
stuff), one for security, etc.
3. The context of course would be an
XML document. I was thinking of something like :
<context>
<actionType>xxxx</actionType>
..
</context>
4. Yes, context need not be that
elaborate, but we do need to divide context into related graphs so that
later the systems can use XPath/XPointer to get specific set of information
they need.
5. FYI, I think context is much more
important from a web services point-of-view and if W3C ever standardized the
context, we could use it at that time. For now we should be able to define a
simple context graph which is relevant to our
work.
Agreed. Do you know where the W3C is with this at the
moment?
6. If we start defining context
now, i.e. what pieces of data do we need , we could "normalize" the
structure after we have identified say 70% of the
information.
All the best,
Mark.
----------------------------------------------
Dr.
Mark Little (mark@arjuna.com)
Transactions Architect,
HP Arjuna Labs
Phone +44 191 2064538
Fax +44 191
2064203