You can configure the footprint of TDB in 32 bit "direct" mode for
smaller datasets:
http://jena.staging.apache.org/documentation/tdb/store-parameters.html
Andy
On 01/04/15 22:38, Stian Soiland-Reyes wrote:
+1 - and how well does the memory mapping of TDB work on Dalvik?
Would jena-sdb work with SQLite?
https://developer.android.com/guide/topics/data/data-storage.html#db
You would probably need https://github.com/SQLDroid/SQLDroid so you
get a JDBC driver.
On 1 April 2015 at 18:02, Claude Warren <[email protected]> wrote:
Might it make sense to use a different persistence engine on Android since
it probably will not have the huge datasets that TDB is designed for. It
might make sense to have a small store available for small devices. Just a
thought.
Claude
On Tue, Mar 31, 2015 at 9:41 PM, Sören Brunk <[email protected]>
wrote:
Hi Andy,
thanks for your feedback and sorry for taking so long to reply. It would
be great to get Android support into mainline Jena and I'm willing to help.
It might be necessary to build an extra jar package for Android though,
similar to what jena-osgi does.
Is there are anything the Jena project can do that would make the
conversion? There may be things that Jena does, or the way is it packaged,
that are inconvenient for you but really make no differnce to the project -
sometimes things are just the way they are because it was done that way but
could easily be done another way. If you have any such points, do email
thsilist or raise a JIRA.
The httpclient issue might resolve itself as soon as Jena is able to
switch to httpclient 4.3. I've looked into the javax.xml issues in more
detail and the good news is that all the xsd datatype classes are actually
there. What's missing are the StAX classes (everything in java.xml.stream)
which seem to be used in ARQ and core (for SPARQL XML result sets, RDF/XML
and TriX) and of course in Xerces. That means it's enough to repackage the
StAX classes from xml-apis and to modify jena-arq, jena-core and
xercesImpl. I've changed my build accordingly.
Android uses XmlPullParser for stream parsing. So another solution could
be to replace StAX with a XmlPull based parsing but I guess that would take
some effort.
On Android, how does TDB work well? TDB uses fairly traditional file
handling for 32 bit machines - "direct mode" - and uses memory mapped I/O
for 64 bit machines - "mapped mode" - if it can detect the mode correctly.
Detection is not subtle, it looks in system property "java.vm.info" and
default to 32 bit. In mapped mode, it does try to use as much memory as
possible which is not friendly to co-resident apps (you can force "direct"
mode programmatically).
Since most Android devices nowadays run on a 32 bit ARM architecture I
guess it will run almost always in direct mode.
But I realized that TDB isn't working at all at the moment, because it
depends on JDK classes that aren't available on Android for things like
getting the PID. I think it is possible to replace those calls by using
similar classes provided by the Android SDK. I will try to get it working.
A dependency on Android specific code would probably make mainline
integration more difficult though.
Sören
--
Dipl. Inf. Sören Brunk
Research Associate
Technische Universität Dresden
Faculty of Computer Science
Institute for Software- and Multimedia-Technology
Junior Professorship in Software Engineering of Ubiquitous Systems
01062 Dresden
--
I like: Like Like - The likeliest place on the web
<http://like-like.xenei.com>
LinkedIn: http://www.linkedin.com/in/claudewarren
