Re: [higgins-dev] IdAS changes proposalPaul,
Actually, I did mean the following:
1. Main point - it is difficult to implement full SPARQL specification in Upper
CP because it is really difficult task. In other words, we can implement
"restricted" SPARQL functionality where some queries will not work.
2. (as you understood) some semantics can't be expressed in the .api CP using
.api.IFilter. For such queries (where regex() is present for an example) Upper
CP will work solwly.
Thanks,
Sergey Lyakhov
----- Original Message -----
From: Paul Trevithick
To: higgins-dev
Cc: Vadym Synakh ; Paul Trevithick ; Igor Tsinman
Sent: Thursday, October 15, 2009 6:41 PM
Subject: Re: [higgins-dev] IdAS changes proposal
Sergey,
Let me see if I understand what you are saying. Are you saying this:
a.. We could implement the .api2 CP as shown below, but it will be
difficult to implement in it many aspects of SPARQL because the semantics can't
be expressed in the .api CP using .api.IFilter.
If yes, then I was thinking was different. I was not assuming that
.api.IFilter semantics were sufficient to express the SPARQL semantics
directly. I was, however, assuming that the upper .api2 CP may in some cases
have to read (using lower .api CP) many, most, and sometimes ALL (!) entities
from the lower .api CP and perform the SPARQL WHERE filtering algorithms
itself. And this is why I was saying that the performance may be very bad when
this two layer approach is taken.
I'm looking for a solution that allows the old .api to be maintained and to
be able to reuse these "old" CPs by adapting them with the upper .api2 CP. If
the performance is too bad, then the developer can implement a "native" (not
two layered) CP using .api2.
--Paul
On 10/15/09 11:27 AM, "Sergey Lyakhov" <[email protected]> wrote:
Paul,
> Do you think it is practical to implement this:
> +----------------------------------------+
> | Upper CP that implements .idas.api2 |
> | SPARQL api but read/writes "raw" |
> | entities/attributes from lower CP |
> +----------------------------------------+
> +----------------------------------------+
> | Lower CP implements existing .idas.api |
> +----------------------------------------+
I think we are able to implement basic aspects of SPARQL which will satisfy
our requirements. However it will be difficult to implement many aspects of
SPARQL such as FILTER functions in WHERE clause (moreover, there is no any
equivalent of those functions in idas.api.IFilter). For example, if I want to
use regex(..) SPARQL FILTER function in Upper CP, I'll need first select all
entities from old CP, and than make additional check selecting entities which
conform to the regexp.
Thanks,
Sergey Lyakhov
----- Original Message -----
From: Paul Trevithick <mailto:[email protected]>
To: higgins-dev <mailto:[email protected]>
Cc: Vadym Synakh <mailto:[email protected]> ; Paul Trevithick
<mailto:[email protected]> ; Igor Tsinman <mailto:[email protected]>
Sent: Thursday, October 15, 2009 4:31 PM
Subject: Re: [higgins-dev] IdAS changes proposal
Sergey,
Hmmm, this is a tough one. We don't want to lose the investments in the
existing CPs (the old .idas.api). Yet we don't want to create a burden for new
CP developers. While we mull this over, I have a question. Do you think it is
practical to implement this:
+----------------------------------------+
| Upper CP that implements .idas.api2 |
| SPARQL api but read/writes "raw" |
| entities/attributes from lower CP |
+----------------------------------------+
+----------------------------------------+
| Lower CP implements existing .idas.api |
+----------------------------------------+
If so, then we could maintain both the lower and the upper APIs. Any CP
that didn't want to support the .api2 (upper api) wouldn't have to, there
because they could use the upper "adapter" CP. The result might be very slow,
but at least it (might) work. And if good SPARQL performance was required,
then the CP would be force to do a native implementation of .idas.api2.
[One really interesting benefit of implementing SPARQL is that with the
above adapter plus a web service front end, we can expose any IdAS data source
as a SPARQL endpoint. Then we'd have XDI and SPARQL endpoints for the
Attribute Service. The Linked Object Data (LOD) semweb folks are creating lots
of SPARQL endpoints-we'd dovetail with these efforts.
--Paul
On 10/15/09 6:23 AM, "Sergey Lyakhov" <[email protected]> wrote:
Paul,
Sorry for delay.
> 3. Jim Sermersheim invented IFilter because we needed something and
SPARQL wasn't yet established. Now that it is, I wonder if we shouldn't give
it another look
It would be very convinient to use SPARQL for RDF-based context
providers (like jena CP). However it would be hard to implement all aspects of
SPARQL for context providers which are not based on RDF (JNDI, XML, Hibernate
etc.).
> When you go to make these changes, it will be critical to load into
your workbench every possible context
> provider that you can find so that you can fix them so that they
don't all break.
It will take a lot of work to implement new filter/model for all
providers. So, I suppose there is a sence to put new IdAS interfaces into a
new project (like org.eclipse.higgins.idas.api2) and than fix all providers to
support these new interfaces. What do you think about this?
Thanks,
Sergey Lyakhov
----- Original Message -----
From: Paul Trevithick <mailto:[email protected]>
To: higgins-dev <mailto:[email protected]>
Cc: Vadym Synakh <mailto:[email protected]> ; Paul Trevithick
<mailto:[email protected]> ; Igor Tsinman <mailto:[email protected]>
Sent: Monday, September 28, 2009 3:11 AM
Subject: Re: [higgins-dev] IdAS changes proposal
Sergey,
My responses:
1.. agree
2.. agree
3.. Jim Sermersheim invented IFilter because we needed something
and SPARQL wasn't yet established. Now that it is, I wonder if we shouldn't
give it another look
4.. (4.1): short answer: no. Longer answer: cdm.owl is an attempt
to approximate in owl concepts that cannot be directly operationalized in
real RDF/OWL based systems. Only higgins.owl should be imported and used.
Cdm.owl is just an attempt at explanation. It can be ignored. (4.2) A lot of
OWL URLS end in .owl, but it isn't a firm requirement or convention.
When you go to make these changes, it will be critical to load into
your workbench every possible context provider that you can find so that you
can fix them so that they don't all break.
--Paul
On 9/23/09 12:07 PM, "Sergey Lyakhov" <[email protected]>
wrote:
Paul,
I suppose, cdm:entityId is redundant and we can use rdf:ID
instead. As a result:
1.1. In this case IEntity.getEntityID() will retun rdf:ID.
1.2. In case of blank entity (previously known as a complex
value) it should return null.
1.3. entityId attribute will be eliminated.
I suppose we need to do the following changes to IdAS interfaces
to be compatible with CDM:
2.1. BlankEntity class has been eliminated from cdm.owl. So, I
suppose we need to do the same for IdAS interfaces and replace IBlankEntity
with IEntity (eliminate IBlankEntity interface).
Because there is no any difference between entity and complex
value, we can define the following:
2.2. If Entity has been created by IContext.addEntity(entityType,
entityID) method, it should always have entityID (should not be a blank
entity). In other words, a unique value should be generated by a context and
used as entityId, if no entityId passed.
2.3. If Entity has been created by IAttribute.addValue(URI)
method, it should be a blank entity.
2.4. If Entity has been added by
IAttribute.addValue(IAttributeValue) it should be the same type as passed
entity. If passed entity is a blank entity, new blank entity should be
created as a copy of passed, otherwise a reference to the existent (non
blank) entity should be created.
2.5. When Entity is deleted, all its subentities which are a
blank entity should be deleted too.
Also we need more flex IFilter API:
3.1. IFilter should be able to query both types of entities as
blank as usual.
3.2. IFilter should be able to query a separate value (entity or
simple value) of any nesting level, not only direct attributes of Entity.
Also I have some notes about CDM:
4.1. CDM.owl contains entityRelation and contextRelation object
properties. Do we need to reflect them in IdAS interfaces?
4.2. Namespase of cdm.owl
http://www.eclipse.org/higgins/ontologies/2008/6/cdm.owl ends with .owl. Is
it correct?
Thanks,
Sergey Lyakhov
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