Federations
Linde, A.E.
What query do I post to get a list of federations from a SAC? What is the structure of a federation assertion?
I’m trying to build a SAC browser/query interface using Flex and wondered if we want to allow the user to select which federations are active for a query. Probably only useful for a query depth of 1?
Also, have we got any SACs available for querying on live servers?
T.
--
Tony Linde
Project Manager
Department of Physics & Astronomy
University of Leicester
Kona Andrews
> Couple of questions and a suggestion:
>
> What query do I post to get a list of federations from a SAC? What is the structure of a federation assertion?
>
> I'm trying to build a SAC browser/query interface using Flex and wondered if we want to allow the user to select which federations are active for a query. Probably only useful for a query depth of 1?
Here are the latest API docs:
http://myskua.org/doc/qsac/interface-http.html
The delegations info is kept in the general SAC metadata; I guess
filtering info as you suggest could go in the incoming query in some
way?
> Also, have we got any SACs available for querying on live servers?
There is generally one here:
http://apps.myskua.org/qsac-latest/
However it isn't currently the latest release (despite the name!)
I'm using a frozen older release, compiled without persistence,
because the relevant tomcat is not running in java 1.6 right now and
can't therefore run the latest release. We really need a separate
tomcat, I think; this one is shared with AstroGrid services not
checked/ready for java 1.6.
K.
--
Kona Andrews k...@roe.ac.uk
AstroGrid Project http://www.astrogrid.org
IfA, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ
Norman Gray
Tony, hello.
On 2009 Feb 13, at 11:25, Linde, A.E. wrote:
> What query do I post to get a list of federations from a SAC? What
> is the structure of a federation assertion?
It's part of the setup of the SAC, rather than an assertion within a
SAC. If you dereference the URL <sac-name>?metadata then you'll get
back the metadata which was used to set up the SAC initially, which is
where the delegations are set up.
> I'm trying to build a SAC browser/query interface using Flex and
> wondered if we want to allow the user to select which federations
> are active for a query. Probably only useful for a query depth of 1?
It's an idea, but since the query consists only of a SPARQL query, and
the delegation happens transparently, it's not obvious where that
limitation would be expressed. It's not impossible to think of
something (for example, we could potentially have a ?delegate=1
parameter on the URL to which the query was posted), but I'd probably
prefer not to implement that until we've got a definite problem with
the dumb/transparent federation we've got now.
> Also, have we got any SACs available for querying on live servers?
We haven't, no. I think that now might be the time to get an EC2
machine up semi-continuously. Any thoughts about that?
See you,
Norman
--
Norman Gray : http://nxg.me.uk
Dept Physics and Astronomy, University of Leicester
Norman Gray
On 2009 Feb 13, at 14:53, Kona Andrews wrote:
> There is generally one here:
> http://apps.myskua.org/qsac-latest/
> However it isn't currently the latest release (despite the name!)
> I'm using a frozen older release, compiled without persistence,
> because the relevant tomcat is not running in java 1.6 right now and
> can't therefore run the latest release. We really need a separate
> tomcat, I think; this one is shared with AstroGrid services not
> checked/ready for java 1.6.
I'd forgotten about that. As an evasion of the Tomcat problems, could
we get the standalone SAC running there? It just needs 'java -jar
qsac-standalone-0.3.jar', with Java 6 on the path. Is the plan.
Linde, A.E.
T.
Linde, A.E.
<cross-domain-policy>
<allow-access-from domain="*"/>
</cross-domain-policy>
Eg see http://www.flexgrocer.com/crossdomain.xml or http://www.cnn.com/crossdomain.xml
T.
Norman Gray
Tony, hello.
On 2009 Feb 13, at 17:39, Linde, A.E. wrote:
> That was quicker than I thought. The root of the server has to have
> a file called 'crossdomain.xml' and this file has to contain:
>
> <cross-domain-policy>
> <allow-access-from domain="*"/>
> </cross-domain-policy>
Is this so that the Flash content in Spacebook/meExperiment is allowed
by Flash to make HTTP connections to a site in another domain? That
seems a bit ass-backwards -- shouldn't the client code be making that
configuration?
Linde, A.E.
T.
On 15/02/2009 16:43, "Norman Gray" <nor...@astro.gla.ac.uk> wrote:
Is this so that the Flash content in Spacebook/meExperiment is allowed
by Flash to make HTTP connections to a site in another domain? That
seems a bit ass-backwards -- shouldn't the client code be making that
configuration?
Linde, A.E.
I got the attached (modified for easier reading) doing a .../sac/tonylinde?metadata call (latest qsac version). If I want to add federations to this, how do I do so? And what format do they need to take?
Ta,
T.
On 13/02/2009 14:54, "Norman Gray" <nor...@astro.gla.ac.uk> wrote:
On 2009 Feb 13, at 11:25, Linde, A.E. wrote:
> What query do I post to get a list of federations from a SAC? What
> is the structure of a federation assertion?
It's part of the setup of the SAC, rather than an assertion within a
SAC. If you dereference the URL <sac-name>?metadata then you'll get
back the metadata which was used to set up the SAC initially, which is
where the delegations are set up.
Norman Gray
Tony, hello.
On 2009 Feb 19, at 12:43, Linde, A.E. wrote:
> I got the attached (modified for easier reading) doing a .../sac/
> tonylinde?metadata call (latest qsac version). If I want to add
> federations to this, how do I do so? And what format do they need to
> take?
When you initially create the SAC, you do so by PUTting some RDF which
sets the SAC description (as described in the tutorial page). Though
come to think of it, I don't see anything like that in the RDF you
included in your message -- are you creating it in a different way?
That metadata might look like:
@prefix dc: <http://purl.org/dc/elements/1.1/>.
@prefix quaestor: <http://ns.eurovotech.org/quaestor#>.
<> dc:description "My SAC";
quaestor:delegatesTo <http://foo/myothersac>.
So the dc:description predicate is giving the SAC's dscription, and
the quaestor:delegatesTo predicate names the SAC delegate.
You can _change_ the metadata, but it's a little more involved, and
requires POSTing something like
<rdf:RDF xmlns:cs='http://purl.org/vocab/changeset/schema#'
xmlns:dc='http://purl.org/dc/elements/1.1/'
xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#'>
<cs:ChangeSet>
<cs:subjectOfChange rdf:resource=''/>
<cs:addition>
<rdf:Statement>
<rdf:object>Test SAC</rdf:object>
<rdf:predicate rdf:resource='http://purl.org/dc/elements/1.1/description'/
>
<rdf:subject rdf:resource=''/>
</rdf:Statement>
</cs:addition>
<cs:removal>
<rdf:Statement>
<rdf:object>My SAC</rdf:object>
<rdf:predicate rdf:resource='http://purl.org/dc/elements/1.1/description'/
>
<rdf:subject rdf:resource=''/>
</rdf:Statement>
</cs:removal>
</cs:ChangeSet>
</rdf:RDF>
...to <.../tonylinde?metadata> with MIME type "application/
vnd.talis.changeset+xml". But I don't think that's necessary yet --
setting up the delegation metadata when the thing is initially created
is probably good enough for now.
Linde, A.E.
Re adding federations though, we’ll need something a lot simpler before making anything live – that’ll be the first thing anyone will want to do, federate to new SACs they find out about. One for a coming iteration perhaps.
Speaking of which: when’s the next telecon?
T.
Kona Andrews
> Speaking of which: when's the next telecon?
Monday any good? Would be good to have one.
Linde, A.E.
T.
Kona Andrews
Weds 11am ?
Linde, A.E.
T.