I can subscribe to the philosophy of
portlets requesting updates to public parameters but why do they need to be
able to request update via markup URLs (i.e. on link activation). Surely, a much
simpler model would be just to let performBlockingInteraction and friends
return/output as well as take as input public parameters? That would tie into
the event model better as portlets would have the chance to coordinate such
updates if an update was a subscribable event.
From: Rich Thompson
Sent: 15 June 2005 14:25
To: WSRP TC
Subject: Re: [wsrp] Additional use
cases for issue #44 (set new public params)
I had taken a to-do from the Interfaces SC to develop
(in conjunction with Stefan, Richard and Mike) a proposal for this portion of
Issue #44. Here is that proposal:
Public Parameters (PP) are another aspect of Consumer state that is exposed to
Portlets (the other two are modes and windowState), Portlets should be able to
request changes to PPs in much the same way as they do modes and windowStates
(on URLs and in responses from pbia and handleEvents).
On URLs: (2 issues)
1. Need to encode 3 pieces of information (request to set a PP, the PPname and
the PPvalue) into 2 places (name=value) when using a querystring and deal with
the reduced set of characters allowed in the path portion ('=' is not allowed).
Templates also introduce an issue with how to encode multiple PPs ...
preferably with the Template only having a single placeholder.
All public parameters specified on a URL are concatenated in the form of
The resulting string is URL encoded (changes '=' into %3D and '&' into %26)
to make it valid in both the querystring and path portions of a URL.
This URL encoded string becomes the value for the wsrp-publicParameter URL
parameter, regardless of whether template processing or Consumer URL rewriting
is in use.
2. How to encode complex PPvalues? I suggest serializing the PPvalue to XML and
URL encoding this XML. The Consumer would then receive the PP, recognize it is
of a complex type (based on PPname) and decode the PPvalue to get the XML.
On Operation responses:
1. Return PP requests via a field much as newMode and newWindowState request
updates to those aspects of Consumer managed state. Suggest this field be of
type QNamedStringArray, though it could be an array of NamedString if we do not
want to introduce a usage of a type from the 'extra' namespace.
05/24/05 07:55 PM
WSRP TC <email@example.com>
Re: [wsrp] Additional use cases for issue #44
(set new public params)
I too am interested in hearing people's current opinions. Our early
coordination discussions considered this carefully. It was decided at
that time to not support two coordination models that delivered equivalent
function. Though I pushed strongly for such a parameter style mechanism,
the subcomittee preferred Events because it not only allowed state to be
transferred but also actions. The current public parameter model was
introduced by me later and was crafted specifically to not step on the the toes
To extend this conversation I would like to pose:
1. We consider
whether publicParameters should be QNames so they can be shared/reused across
producers. Note: this is likely needed whether we stick with events or
add the ability to encode a public parameter directly in the URL.
We consider adding a new "defined
event" called publicParameterValueChanged. The payload of this event
would be the QName of the parameter and an Object any holding the parmeter
value [though it might be nice to support our Any/String optional pair style here].
We consider defining the meaning of
publicParameter whose capability contains the value "required" as
meaning that normal usage of this portlet requires the consumer to provide this
value. The portlet would still have to deal with situations in which this
wasn't provided but likely an end-user would consider this usage
crufty/abnormal. For example if a portlet required a CustID parameter and
didn't receive one it could display a view that asks for a custID. The
key here by saying "required" [we can choose a different capability
name] the consumer can distinguish between those public parameters that have a
secondary impact on the portlet [optional] and those that have a primary or
important impact [required].
Stefan Hepper wrote:
I've some use cases that may be a good match for the ability to set new public
parameters by the producer and to encode public parameters in URls by the
1. displaying content based on a specific product id:
- Portlet A allows to select a product from a list
- User clicks on a specific product
- Portlet B renders details of this product
- Portlet C renders currently available number of items on stock for this
- user wants to bookmark this result in order to come back to product tomorrow
implementation with events:
Portlet A encodes the customer selection URLs as POST action links
Portlet A receives a performBlockingInteraction call
Portlet A returns event productID=10
Portlet B receive a blocking handleEvents call for productID=10 and returns new
Portlet C receive a blocking handleEvents call for productID=10 and returns new
implementation with public params:
Portlet A encodes the product selection URLs as GET render links with the
productID as public param
Portlet A receives a render call with the public param productID=10
Portlet B receives a render call with the public param productID=10
Portlet C receives a render call with the public param productID=10
which would be much more efficient and also consistent with the W3C
architecture as links that do only change view state should be encoded as GET
2. display content based on a specific customer id
3. display content based on the selected state of a map
portlet A displays a map of USA
portlet B displays information on the selected state (# people registered,
portlet C displays all IBM labs in that state
and many more.
This would allow to have some gobal navigational state that can be set via URLs
by portlets. Also portlets may want to set new public params as a result of an
blocking interaction or a handle event call.
What do you think?
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