Hi,
I find that a *granuarly* designed AJAX UI can easily issue 100s of
queries per "page". In general, what happens is the following:
You have one query to get a list of resources
select ?person where { ?person a foaf:Person }
Then for each of these, you create a new UI part which will itself
issue several queries, one for each property
select ?name where { ?person foaf:name ?name }
select ?image where { ?person foaf:depiction ?image }
Roughly speaking, you get something like this:
HTTP message 0:
select ?person where { ?person a foaf:Person }
HTTP message 2:
select ?name where { <urn:person1> foaf:name ?name }
HTTP message 3:
select ?image where { <urn:person1> foaf:depiction ?image }
HTTP message 4:
select ?name where { <urn:person2> foaf:name ?name }
HTTP message 5:
select ?image where { <urn:person2> foaf:depiction ?image }
HTTP message 6:
select ?name where { <urn:person3> foaf:name ?name }
HTTP message 7:
select ?image where { <urn:person3> foaf:depiction ?image }
HTTP message 8:
select ?name where { <urn:person4> foaf:name ?name }
HTTP message 9:
select ?image where { <urn:person4> foaf:depiction ?image }
This has obvious performance implications in terms of perceived
performance as the page may take 10s of seconds to fully load.
I know, I know. The ideal situation would be to roll this up into one query.
HTTP message 0:
select distinct * where { ?person a foaf:Person; foaf:name ?name;
foaf:depiction ?image }
But the tradeoff is that you need to let go the granularity of the
Model on the consuming side. No more Person.getAll() and then
Person.getName(), Person.getLastName() API calls.
This is a typical problem with DAOs and Beans in the java world or any
kind of ORM in the general sense.
For most situations, however, SPARQL is expressive ( and graphy )
enough that you let go your "model" altogether and thus going with the
"one big query" is a viable options.
But sometimes you just can't, because you have a lot of business code
in between.
And, yeah, I am also removing stored procedures as a viable option (
because you might not control the SPARQL endpoint ).
So, sorry for the convolutions but I wanted to close the doors for the
obvious answers stated above.
Now, is there a way to do something like this?
HTTP message 0:
select ?person where { ?person a foaf:Person }
HTTP message 1:
select ?name where { <urn:person1> foaf:name ?name }
select ?image where { <urn:person1> foaf:depiction ?image }
select ?name where { <urn:person2> foaf:name ?name }
select ?image where { <urn:person2> foaf:depiction ?image }
select ?name where { <urn:person3> foaf:name ?name }
select ?image where { <urn:person3> foaf:depiction ?image }
select ?name where { <urn:person4> foaf:name ?name }
select ?image where { <urn:person4> foaf:depiction ?image }
and for each request get a multi-part response or something?
That would dramatically slice network costs.
Regards,
A
--
Aldo Bucchi
@aldonline
skype:aldo.bucchi
http://aldobucchi.com/
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