Re: [wsia] Follow-on Example

[Michael Freedman <Michael.Freedman@oracle.com>]

Eilon,
   Oracle's approach/point of view (on the web approach) is as follows:
    a) we strongly discourage portlets from maintaining any kind of
transient state.  We have found that even with moderate sized user
communities, stateless portlets lead to significantly improved portal
response times.  So our preferred solution for your reservation scenario is
(0):  there is neither a session nor a transient entity.  The reservation
state is maintained by encoding the information in URLs inserted into the
generate response content.  I.e. only use sessions when state must be shared
between entities.
    b) recognizing that sessions will be used however, the base scenario
should be one in which the two reservation portlets cooperatively run in the
same session.  In this scenario the two portlets would be responsible for
namespacing encoding their session data to avoid collisions.  This is
analogous to the (servlet) web model though obviously a more insidious
situation as servlets often (safely) assume only one "instance" runs in a
session.  All we would need to do to support this would be ensure that a
portlet is able to determine and use a "key" that distinguishes one use (on
a page) from another.  If this key/id were generated by the consumer, the
consumer could easily choose an algorithm for generating such an id that is
repeatable without maintaining any dynamic (state) information.  Hence the
ID would have little/no cost.

   For us/me the above completely covers Approach 1: the web approach.  It
allows multiple entities of the same type to run in a session with entity
private session data while still allowing these same entities to share
session data between themselves of entities of other types.

The outstanding question is whether we consider the situation where a
portlet only has entity private data so common that we should allow for them
to be so declared and mandate the consumer honor such a declaration?
Personally, I think this is reasonable.  Not having to partition (namespace)
the session would be useful to such developers.  And I think this occurs
commonly enough for us to represent formally.

Another scenario to consider is one where a set of entities want to share a
session distinguished from another set running in the same consumer.  This
is a situation where a service provides 2 portlets designed to work
together.  For example a news feed display portlet and a topic portlet.  If
2 sets of these run is the same page how is one set's session data isolated
from the other?  My answer is that the consumer merely chooses to establish
2 sessions (vs. one) and passes the correct session ID to each set.  I
further believe we shouldn't define how a consumer chooses/learns to do
this.  I.e. I don't think we should define producer meta data that describes
potential groupings for its sessions.  Rather, portlets must expect that the
consumer will potentially run all of these entities in the same session and
behave accordingly.  In many circumstances this may mean that the sets
trounce each others shared data.  However, well coded portlets could choose
to represent this demarcation in its own settable configuration data for the
portlets.  I.e. the config screen could have a setting for group id allowing
the page developer to set a common group id for the 2 portlets in each set.
      -Mike-