heavy duty query visualization
notmart at gmail.com
Fri Oct 14 20:13:21 UTC 2011
in Plasma Active one things like the activity screen that shows all the
nepomuk resources, the ui to search and add a new one, the image viewer (that
lists all objects of type image) use the plasma metadata dataengine.
this one is basically just a wrapper around Nepomuk QueryClient.
due to the architecture of plasma dataengines, this is not so much efficient,
since a quite too much of data copy around is involved.
in the next releases we want to do more fancy stuff, like a central kick ass
document browser that lets browse stuff by basically anything, type, date,
rating,tags,activities, whatever and combining all of this.
what i'm trying to do now, is a QAbstractItemModel (working prototype in the
plasma-mobile repo, mart/nepomukmodel branch) that is done expressively to
show resources from a query, to be instantiated from QML, so some questions
surface, related both to performance issues and nepomuk usage.
* lazy loading: if i do a query with really a lot of restults, would be
possible to limit it like a relational database, to know how many results
there are, asking for the first 10, then from 11 to 20 and so on? (if a query
has something like 2000 results that would be hady;)
* sorting: is it possible to directly sort the results based on one of the
properties? in this case i wouldn't have to load the whole model in memory
from the beginning
* property watching: if i understood correctly to dynamically update property
values i have to use Nepomuk::ResourceWatcher that stays
nepomukdatamanagement, still semi private in kde-runtime, right?
bindings to it doesn't sound like fun ;) as isn't brutally exposing sparql to
qml. What i'm thinking to do here is:
* pass queries by string, so with the more limited desktopquery language.
* expose to js some functions to limit the results, like limitByType(),
limitByActivity() limitByTag() etc. this will with the c++ api add the needed
parameters to a query precedently created from a string
* what queries are possible? how? I think many of the queries we will need
will be to build things tagcloud-ish, so besides a proper tagcloud that has
been possible to do in nepomuk since a while, other needed things could be
series of result like:
* resource type, number of occurrencies
* rating, number of occurrencies
* date interval (like month) number
and so on. is this easily feasible? (this will probably go in the dataengine,
not in the model)
* for the write part, like assigning a score, a tag, connect to activity: this
will be done exactly like now with a plasma service, in this case created not
by the dataengine but by the model
comments? ideas? opinions?
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