Thanks, Steve.
I may have to use dc:identifier. Creating a RELS-EXT stream just to
solve this particular issue isn't worth the effort.
As for objective: I'd like to use the PID's namespace to distinguish
between 'approved' objects and objects which are 'work-in-progress'. The
approved objects will be indexed and searchable via Lucene/Solr on a
public web-site whereas the 'work-in-progress' objects will deliberately
be excluded from that index.
Consequently, my data management application needs to retrieve
'work-in-progress' objects by PID namespace.
That's possible via the REST API 'findObjects' method - but it doesn't
have the 'order by' clause so I'd have to do any ordering within my
application - certainly possible but less efficient. I'd hoped to use
iTQL to have Mulgara do the ordering.
I guess I'll have to request an enhancement to the REST API.
Janna
Steve Bayliss wrote:
I believe that dc:identifier is your only option - unless you create
your own triple in RELS-EXT, with a literal object corresponding to
the PID - there is no other triple that is automatically created that
as the PID as a literal object.
I see that you are actually restricting your query on the PID being
"demo*" - ie on the namespace part of the PID.
What is your overall objective with this "PID=demo*" part of the
query? Are you trying to exclude "system" objects and only include
"user" objects?
-----Original Message-----
*From:* Janna Wemekamp [mailto:[email protected]]
*Sent:* 15 April 2009 01:45
*To:* Steve Bayliss
*Cc:* [email protected]; 'Gramsbergen, Egbert'
*Subject:* Re: [Fedora-commons-users] Questions re iTQL queries
involving PIDs
Yes, querying the DC identifier will work but I'd really prefer
not to build that assumption into my application.
One of the reasons I'm experimenting with FC's Resource Index
Search API is that iTQL has an *'order by'* clause unlike the REST
API's *'findObjects'* method. If the REST API provided an *'order
by'* clause, I probably wouldn't need to use iTQL.
Thanks for your suggestion, though.
Janna
Steve Bayliss wrote:
I think using
and $object <dc:identifier> 'demo*' in <#ri-fullText>
in the full-text part of your where clause should work (ie the
equivalent of has-pid is to search for the dc:identifier).
Obviously this depends on what values you are actually putting in
dc:identifier in the DC datastream; I'm assuming from your
earlier examples that you are just putting the PID in this field.
NB you need to make sure you have turned on full-text indexing.
-----Original Message-----
*From:* Janna Wemekamp [mailto:[email protected]]
*Sent:* 14 April 2009 02:20
*To:* Steve Bayliss
*Cc:* [email protected]
<mailto:[email protected]>;
'Gramsbergen, Egbert'
*Subject:* Re: [Fedora-commons-users] Questions re iTQL queries
involving PIDs
Hi all,
Thanks very much Steve; your comments did help!
I had mis-interpreted the Mulgara documentation on
<mulgara:is> which states that it requires a non-variable
value as its object. I had assumed the non-variable value had
to be a literal.
(My apologies to Egbert who indicated that earlier.)
Still unresolved is the more general query I posed in the
original posting:
select $object, $label, $identifier
from <#ri>
where $object <fedora-model:label> $label
and $object <dc:identifier> $identifier
and $object <has_pid> 'demo*' in <#ri-fullText>
How does one specify the <has_pid> predicate/property in this
query?
I suspect it's not possible - anyone able to confirm that?
Cheers!
Janna
Steve Bayliss wrote:
You've got a mistake still in your query
> /and $object <mulgara:is> 'info:fedora/demo:10' /
You should be specifying your Fedora object identifier as a
URI, not a literal, ie
//
/and $object <mulgara:is> <info:fedora/demo:10> /
There's no such thing as "the '$object' concept" - $object
is simply a variable; you can substitue $object with $x (or
$pid) and get the same results.
NB for debugging, it's sometimes useful to show all
relationships for a particular object, so that you can see
what triples actually exist whilst debugging a query, for
this you can use something like
select $s $p $o
from <#ri>
where
$s $p $o
and
$s <mulgara:is> <info:fedora/demo:10>
Hope that helps
Steve
-----Original Message-----
*From:* Janna Wemekamp [mailto:[email protected]]
*Sent:* 09 April 2009 04:31
*To:* Gramsbergen, Egbert
*Cc:* [email protected]
<mailto:[email protected]>
*Subject:* Re: [Fedora-commons-users] Questions re iTQL
queries involving PIDs
Thanks for the responses.
However, the query
/select $object $label $identifier $state
from <#ri>
where $object <fedora-model:label> $label
and $object <dc:identifier> $identifier
and $object <fedora-model:state> $state
and $object <mulgara:is> 'info:fedora/demo:10'/
doesn't return any results either. (Yes, there is an
object with pid demo:10.)
I'm beginning to wonder whether '$object' and 'pid' are
considered quite
different beasties by FedoraCommons even though they
'look' the same in a query
result...
(And, I have read the documentation on the mulgara
web-site several times. It
doesn't define the '$object' concept.)
Cheers.
Janna Wemekamp
Gramsbergen, Egbert wrote:
Back to the original question: try with
$object <mulgara:is> <info:fedora/demo:10>
That should work.
Success,
Egbert Gramsbergen
-----Original Message-----
From: arne anka [mailto:[email protected]]
Sent: Wed 4/8/2009 12:37 PM
To: [email protected]
<mailto:[email protected]>
Subject: Re: [Fedora-commons-users] Questions re iTQL
queries involving PIDs
fighting with itql since yesterday again ...
> (1) The query:
>
> select $object from <#ri> where $object
<mulgara:is> 'demo'
>
> returns a single element:
>
> <result>
> <object>demo</object>
> </result>
>
> even though there is no object in the repository with
this PID.
of course it does -- you defined that $object _is_ 'demo'.
so, that's what you get.
> I'd like to be able to issue queries like:
>
> select $object $label $identifier $state
> from <#ri>
> where $object <fedora-model:label> $label
> and $object <dc:identifier> $identifier
> and $object <fedora-model:state> $state
> and $object <mulgara:is> 'demo:10'
>
> This query returns no results even though the PID
'demo:10' exists.
> What am I doing wrong?
you never really got $object -- what you do is saying
that $object has the
model $label.
but since $label is never assigned a value ...
> (2) I'd also like to perform wild-card searches on
PIDs; for example
>
> select $object, $label, $identifier
> from <#ri>
> where $object <fedora-model:label> $label
> and $object <dc:identifier> $identifier
> and $object <has_pid> 'demo*' in <#ri-fullText>
>
> How does one specify the <has_pid> predicate/property
in this query?
you might be able to taht with 'having'
> The following works quite happily but I'd not like to
assume that the DC
> identifier always matched the PID.
>
> select $object $label $identifier
> from <#ri>
> where $object <fedora-model:label> $label
> and $object <fedora-model:ownerId> $ownerId
> and $object <dc:identifier> $identifier
> and $object <dc:identifier> 'demo*' in
<#ri-fullText>
>
well, basically, $object should be your id -- what you
are doing wrong is
getting $object at all.
imo it has to go like that:
select $object $label $identifier from <#ri> where $object
<fedora-model:hasModel> <info:fedora/my:model> and ...
or for your label (untested) something like:
select $object $label $identifier from <#ri> where $object
<fedora-model:label> 'a label name' and ...
see http://docs.mulgara.org/itqlcommands/select.html
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