[Rets-dev] Comments on RQL, SQL, XPath and Joins, Why not RDF/OWL?
Jery Cook
twoencore at hotmail.com
Mon Jul 9 15:07:17 CDT 2007
W3C Recommendations: Resource Description Framework (RDF) and Web Ontology
Language (OWL).
The World Wide Web Consortium has announced "final approval of two key
Semantic Web technologies, the revised Resource Description Framework (RDF)
and the Web Ontology Language (OWL). RDF and OWL are Semantic Web standards
that provide a framework for asset management, enterprise integration and
the sharing and reuse of data on the Web. These standard formats for data
sharing span application, enterprise, and community boundaries, since
different types of users can share the same information even if they don't
share the same software."
The Resource Description Framework (RDF) is a "language for representing
information about resources in the World Wide Web. It is particularly
intended for representing metadata about Web resources, such as the title,
author, and modification date of a Web page, copyright and licensing
information about a Web document, or the availability schedule for some
shared resource. However, by generalizing the concept of a 'Web resource',
RDF can also be used to represent information about things that can be
identified on the Web, even when they cannot be directly retrieved on the
Web. Examples include information about items available from on-line
shopping facilities (e.g., information about specifications, prices, and
availability), or the description of a Web user's preferences for
information delivery." The W3C RDF Recommendation is presented six parts:
Primer, Concepts, Syntax, Semantics, Vocabulary, and Test Cases.
The OWL Web Ontology Language is "intended to be used when the information
contained in documents needs to be processed by applications, as opposed to
situations where the content only needs to be presented to humans. OWL can
be used to explicitly represent the meaning of terms in vocabularies and the
relationships between those terms. This representation of terms and their
interrelationships is called an ontology. OWL has more facilities for
expressing meaning and semantics than XML, RDF, and RDF-S, and thus OWL goes
beyond these languages in its ability to represent machine interpretable
content on the Web. OWL is a revision of the DAML+OIL web ontology language
incorporating lessons learned from the design and application of DAML+OIL."
W3C has published the OWL Recommendation in six documents: Use Cases,
Overview, Guide, Language Reference, Test Cases, and Language Semantics and
Abstract Syntax.
Sounds like a perfect match for Rets to me.
Jeryl Cook
_____
From: Jery Cook [mailto:twoencore at hotmail.com]
Sent: Monday, July 09, 2007 11:10 AM
To: 'jbrush at ronintech.org'; 'E-mail Rets-Dev'; 'rets-users at rets.org'
Subject: RE: [Rets-dev] Comments on RQL, SQL, XPath and Joins, Why not
RDF/OWL?
The RDF,RDFS,OWL specifications are final by the W3 in 2004, it is not a
question of maturity or complexity it is simply do you want do move forward
with it. The benefits of having RETs standard converted to an Ontology,
while having SPARQL endpoints, would be massive.., not to mention so many
other tools that can be used as clients to RDF(RETs repositories)
I have
been subscribed to this news letter for almost a year
I see the same
questions come up over and over, about how do I query this, and that, .why
can’t I just query for images with a criteria, why is it hard to find
clients to Rets server, etc. using RDF/OWL to describe your domain
model,(Real estate information) will effectively represent the
structure/meaning of the information as well as give developers/machine the
an effective way to query and extract that information.
you all are doing a great job with the standard, it just looks from my
perspective it needs to be taking to the next level.
I recommend the RETs community seriously considered having RDF/OWL on there
roadmap sooner, rather than later.
References:
http://xml.coverpages.org/ni2004-02-10-a.html
http://www.semantra.com/pdf/literature/CIOs-guide-to-semantics.pdf
<http://www.innodata-isogen.com/knowledge_wise/index_html>
Jeryl Cook
_____
From: Jeff Brush [mailto:jeffbrush at hotmail.com]
Sent: Thursday, May 10, 2007 6:24 PM
To: Jery Cook; 'E-mail Rets-Dev'
Subject: RE: [Rets-dev] Comments on RQL, SQL, XPath and Joins
Jeryl,
Technologies such as RDF, RDF Schema, OWL (Lite) and DAML+OIL were
reviewed by Bruce Toback and myself very early on in the RETS2 development
process. They were found to be too complicated and not ubiquitous enough for
general use in the RETS standard at that time.
When semantic web technologies become more mainstream I am sure these types
of technologies will be considered for inclusion by the community.
Jeff Brush
Ronin Technologies
BTW-You're sig is spot on-IMHO.
_____
> From: twoencore at hotmail.com
> To: matt at pmptechnology.com; pstusiak at falcontechnologies.com;
rets-dev at rets.org
> Subject: RE: [Rets-dev] Comments on RQL, SQL, XPath and Joins
> Date: Thu, 10 May 2007 17:21:40 -0400
> CC:
>
> Standards, standards :)
>
> Why not use RDF/OWL to describe RETS,
> Use a tool like D2RQ that sits on a MLS database...expose the data via
> SPARQL(SQL-like web query language).
>
> D2RQ
> http://sites.wiwiss.fu-berlin.de/suhl/bizer/D2RQ/
>
> xml schemas , and RDF/OWL
>
http://www.pacificspirit.com/Authoring/Compatibility/OWLRDFExtensibility.htm
> l
>
> SPARQL
> http://en.wikipedia.org/wiki/SPARQL
>
>
> someone could simply have a repository of SPARQL web-service endpoints to
> RETS systems across the US...
>
> Jeryl Cook
>
> "I don't know the key to success, but the key to failure is to try to
please
> everyone."
> -Bill Cosby
> -----Original Message-----
> From: rets-dev-bounces at rets.org [mailto:rets-dev-bounces at rets.org] On
Behalf
> Of Matt Lavallee
> Sent: Thursday, May 10, 2007 12:35 PM
> To: 'Paul Stusiak'; 'E-mail Rets-Dev'
> Subject: RE: [Rets-dev] Comments on RQL, SQL, XPath and Joins
>
> Paul, et al.,
>
> Thanks for the background information on how RQL came to be chosen. Paul's
> point at the end does echo my sentiment in the earlier thread, knowing
full
> well
> that implementing XPath is a sea-change from providing a pseudo-SQL-to-SQL
> translator, with potentially limited return.
>
> However, with all due deference to the MLS Vendors, there is a genuine
need
> for
> some sort of "glue" operation to deal with the new distribution of data. I
> sincerely feel it's unreasonable to expect three (or more) queries to get
> related information strictly because of an inadequate querying interface
--
> particularly when we know that the data store itself supports such
> operations.
>
> Now, whether that glue be a graceful evaluation of the hierarchical data
(as
> in
> my implicit-relation RQL example) or a classic RDBMS implementation of
JOINs
> doesn't really matter to me... but I think one of the two needs to exist
to
> consider the query feature functional.
>
> Also, if Media doesn't have a Resource type of its own, how can one query
> for
> Media without using a schema?
>
> -Matt
>
> > -----Original Message-----
> > From: rets-dev-bounces at rets.org [mailto:rets-dev-bounces at rets.org] On
> Behalf
> > Of Paul Stusiak
> > Sent: Tuesday, May 08, 2007 12:18 PM
> > To: E-mail Rets-Dev
> > Subject: [Rets-dev] Comments on RQL, SQL, XPath and Joins
> >
> > There have been some comments on the rets-dev list recently about
> > querying in RETS2
> >
> > Some background may help people understand where we are.
> >
> > The original RETS2 documents included DMQL2 and XPath. Some feedback
> > from surveys indicated that there was a significant group of developers,
> > those who did not come to the meetings were having conceptual problems
> > with DMQL. Specifically, they were asking questions like "why isn't it
> > SQL? we understand SQL..." With some more digging, some of the concerns
> > boiled down to the use of symbols for logic operations. There had been
> > an intent to replace DMQL2 with something like DMQL3 - fixing several of
> > the problems with the BNF of DMQL2 that caused difficulty when using
> > parser-generators like antlr and others.
> >
> > There had been a group, I think Sergio and Steve and Stuart were part of
> > it, to evaluate the future direction for querying. I don't see the
> > document on rets.org, so I've asked Sergio if he can find it and post it
> > to rets-dev and we'll put it up on the website.
> >
> > My recollection is that this group looked at DMQL, XPath and SQL and
> > determined that DMQL was the way to go.
> >
> > Given these facts, the work on RETS2 focused on DMQL and had some XPath
> > included because it is a natural for XML. An alternative was proposed by
> > Wantao Zhou of FirstAmerican. This was to XML-ify the DMQL. It was well
> > thought out, but was not considered appropriate by the community.
> >
> > As the work on DMQL2+ was going on, it was pointed out that Dave Dribbin
> > and Keith Garner of CRT had already done some of this work in one of
> > their products that were open source. Dave reworked some of the BNF to
> > have only the feature set of DMQL2. This was a properly formed BNF that
> > resolved some of the issues that made it more difficult to feed to
> > parser-generators and added some syntactic candy by changing the '|',
> > etc. with 'OR'. No change of intent, but the syntactic candy should help
> > those who were thrown off by the different operator representation.
> >
> > RQL appears to offer protection of the existing substantial investment
> > in DMQL that server vendors have while providing response to some of the
> > impediments to adoption that the different operator representations
cause.
> >
> > As RETS2 went forward with the inclusion of XPath, there was a lot of
> > resistance to using it from the existing vendors. To get agreement on
> > RETS2, it was removed from the Service document. The Service document
> > does permit additional query languages but mandates only RQL. It is
> > possible that cutting XPath from RETS2 was incorrect.
> >
> > I would also point out that the RETS2 specification is a suite of
> > documents. There may be additional documents that need to be added.
> >
> > While SQL is the language used on the repository for RETS1 - there were
> > only two vendors who were using other storage techniques than a
> > relational database that I know of, not all storage solutions use SQL.
> > The specification has attempted to separate the specification from the
> > implementation.
> >
> > --
> > Paul Stusiak
> > Falcon Technologies Corp.
> >
> > _______________________________________________
> > Rets-dev mailing list
> > Rets-dev at rets.org
> > http://lists.rets.org/mailman/listinfo/rets-dev
>
>
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