[Laszlo-dev] Implicit replication, <view> datapath property, and, <datapath> xpath property

[André Bargull]

What do you actually plan to do for states, because through states 
you'll get dynamic constraints, so dynamic method attachment/detachment, 
too.
You've wrote once about a LzConstraint-class, but I can't quite remember 
in which context. If you had this LzConstraint-class, couldn't you 
add/remove constraints more easily at runtime?
So specifically for implicit replication, you'd only remove the 
datapath-/xpath-constraint from the source-node's datapath and attach it 
to the replication-manager and that's it.

Also keep in mind, that currently constraint datapaths aren't fully 
"bug-free", i.e. LPP-4209 or LPP-5353.

On 2/8/2008 1:46 PM, P T Withington wrote:
> True.  And this I think is one of the complaints about implicit 
> replication, that it is unpredictable.
>
> The alternative is that implicit replication will just have to be 
> slower than explicit (because it needs to do this dynamic method 
> detachment and attachment at runtime, rather than being able to be 
> analyzed at compile time).  That would certainly be another way to 
> deprecate implicit replication!  :)
>
> On 2008-02-07, at 17:24 EST, André Bargull wrote:
>
>> But you need to consider, that the constraint does not apply to a 
>> replication-manager in every case! If the xpath-expression points to 
>> a single node, replication isn't triggered and therefore no 
>> replication-manager will be created. If you just replace all 
>> constraint datapaths with explicit replication, many programs will 
>> break, because people don't expect to get a replicator-node in this 
>> cases.
>>
>>> Delving into making constraints class methods, we have some tag- 
>>> compiler work to do.
>>>
>>> Apparently you can say:
>>>
>>>   <view datapath="${...}" />
>>>
>>> or:
>>>
>>>   <view>
>>>     <datapath xpath="${...}" />
>>>
>>> In both cases, the constraint really applies to the (invisible)  
>>> replication manager, not to the view or the datapath.  Right now 
>>> this  constraint is picked up at run time, ripped off the clone 
>>> template and  smashed onto the replication manager.  That is not 
>>> going to work in  modern (JS2) runtimes.
>>>
>>> I think the right approach here is to have the tag compiler 
>>> re-write  implicit replication into explicit replication, so:
>>>
>>>   <view datapath="${...}" />
>>>
>>> becomes:
>>>
>>>   <replicator datapath="${...}">
>>>     <view />
>>>   </replicator>
>>>
>>> etc.
>>>
>>> Does this seem feasible?  Could we even spit out a deprecation 
>>> warning  suggesting that explicit replication be used?
>>
>
>