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Re: [ontolog-forum] Ontology-based database integration

To: "[ontolog-forum]" <ontolog-forum@xxxxxxxxxxxxxxxx>
From: "Len Yabloko" <lenya@xxxxxxxxxxxxx>
Date: Wed, 07 Oct 2009 00:05:52 +0000
Message-id: <W7391319283251861254873952@webmail32>
>Len Yabloko wrote:
>> As I said - OntoBase is designed to simplify data integration and database 
>application development by taking advantage of ontology-based semantic 
>modeling. Part of the method used in OntoBase is semi-automatic generation of 
>ontology guided by the user, who *is* the main source of semantics. Database 
>metadata is used to ensure consistency of the end result and , at the same 
>time, to provide automatic translation of the application activity into 
>database transactions. None of these goals was ever set or accomplished by the 
>above mentioned Semantic Web initiatives. 
>They were, however, the objective of several "semantic database 
>integration" and "semantics-based federation of distributed databases" 
>projects of the 1980s.  As I remember, there was an entire issue of the 
>ACM Journal devoted to such projects, long about 1988.  Of course, the 
>integrating ontology wasn't called an "ontology" in that time; it was 
>called a "semantic data model", with such languages as SDM and OSAM*.  
>(Sudha Ram of U. Arizona published a compendium of "semantic data 
>modeling concepts" in 1990, with a bibliography of the tower of Babel of 
>that time.  I rather shamelessly plagiarized her concepts list for my 
>presentation of "OWL as a Data Modeling Language".)  NIST built similar 
>tooling back then, and we later used a commercial tool called ORION that 
>was a spinoff of some DARPA project (brainchild of Amit Sheth and some 
>other famous names).  (More lore from the ancient world before PDF, but 
>not nearly so interesting as the Dead Sea Scrolls.)
Thank you for the references. I consider OntoBase an evolution of these 
existing methods. In fact, OntoBase generates semantics models in Protege frame 
format which can be directly translated to OWL inside Protege. However,  the 
original link given by Kingsley that I was referring to as "Semantic Web 
initiatives" was not about using OWL for semantic modeling. Here it is again:
Let me quote from the introduction:
" the role of RDF as an integration platform for data from multiple sources, 
primarily in form of RDB, is one of the main motivations driving research 
efforts in mapping RDB to RDF"
Of course Semantic Web technologies are expanding now into these old 
territories you have referenced with such detail and accuracy. But one has to 
be very careful not to confuse semantic modeling with data modeling and data 
linking with data integration. And ,indeed, not to confuse model-theoretic 
semantics (developed by Tarski for first order logic and claimed by RDF) with 
various other semantics.     (01)

>The major difference in using OWL as the language for the integrating 
>model is that it is a standard language that is well-defined and comes 
>with a variety of supporting tools for validating the ontology itself.  
>In addition, it offers the possibility of extension to additional 
>information bases by linking to additional ontologies, assuming that the 
>"integrating ontology" is one, and is not just the OWL version of a 
>purpose-built SDM model.  (And it is easy to make tools with much nicer 
>GUIs now.)  Unfortunately, many/most databases are treated as having 
>inherent "closed world" semantics, which may make it difficult to get a 
>"semantic web language" to support some important semantics of the 
>databases.    (02)

Yes, and that is one reason not to assume that Semantic Web is fully equipped 
to deal with data integration. I believe OWL itself is an attempt to go around 
the inherent limitations of Semantic Web. But simply attaching the word 
Ontology to Semantic Web does not quite addressed the issue. So I would prefer  
ontology to be its own independent area of research rather than having 
secondary role given to it by Semantic Web.    (03)

>Ian's point is well-taken:
>>> I spent years mapping legacy data into "semantically richer" formats ...,   
>and it always comes down
>>> to the data, not the data model. You can guarantee the data modeller got it
>>> wrong when they built the system, and the users have been working against
>>> rather than with the model for years. Unless you have a good sniff around in
>>> the data, you'll never get a real picture of the true semantics (i.e. what
>>> the data is actually referring to in the real world). ...
>The data modeler needn't have got it wrong, initially.  The problem is 
>that the databases are, for various reasons, rigid, and are not easily 
>evolved when the business practices or business environments change.  
>So, over time, the schema becomes gradually more and more out of sync 
>with the reality of the business, and some bits no longer have any 
>vestige of their original intent. (I am reminded of the executive who 
>told me: "I know that is what the DB document says, but what my staff 
>puts in that field is X, and we are the only ones who still use that 
>field."  Unfortunately, he was wrong about the last.)
>Len wrote:
>> The project I do for DoD calls this process Semantic Model Discovery. 
>Actually, there are many models some times used in turns, and they all are 
>Yes.  That agrees with my experience.  In a big enough organization, 
>there is more than one (mis-)use of certain DB elements, and over time 
>some will no longer be used and others will appear.  But the schema will 
>live on.
>> They main goal of data integration should be maintaining consistent mapping 
>between different semantic models. The main challenge is to define what 
>"consistent" means. 
>Uh, yeah.  The statement of the task strikes me as an oxymoron.  I would 
>have thought that your OntoBase was about linking multiple data 
>organizations and representations to a common semantics, rather than the 
>other way around.  Perhaps I misunderstand...    (04)

The main problem is to arrive to "common semantics". To accomplish that one 
needs to consider alternative semantic models compatible with data models 
enforced by data sources. This is what OntoBase allows you to do. But you can't 
stop even after arriving to mutually compatible model, because new sources can 
be added and new users may introduce new use cases (or abuse cases ,if you 
insist)     (05)

>> This where Chris Partridge's work first opened my eyes on true mature of 
>semantics, as opposed to mathematical notion of 1st order logic some times 
>confused with semantics (I know this statement will provoke discussion)
>I have seen a lot of things confused with "semantics", because the 
>interpretation of "semantics" is usually "what this means for _my_ level 
>of abstraction, purpose, and domain of interest", and it often makes the 
>assumption that "my" is synonymous with "our common" or "everyone's".  
>But anyone who confuses formal logic with semantics understands neither. 
>    (06)

I have been following these forum long enough to have heard all kinds of claims 
about what is Semantics and many of these claims were tying it directly to FOL, 
like no other logic or semantics ever existed.    (07)

>Formal logic is a means of expression, in which the basic elements of 
>the language have well-defined meanings and a set of well-defined 
>manipulations retain those meanings, and nothing more.  As to whether 
>the snark actually is a boojum, classical formal logic offers only two 
>possible interpretations:  it is either true or it is false, and it 
>cannot be both.  And if you make a set of statements that allow the 
>well-defined manipulations to produce a result of "true", then it does.  
>That's all there is; there ain't no more.  Formal logic is about "how to 
>think"; it is not about what you think about.
>P.S. Ian:
>>> I never had a formal method for re-engineering data in those days. In recent
>>> years I've been using Chris Partridge's BORO Method. It seems to work pretty
>>> well as far as I can tell. Don't tell him I said that though.
>Since Chris is a frequent contributor to this exploder, your secret is 
>Edward J. Barkmeyer                        Email: edbark@xxxxxxxx
>National Institute of Standards & Technology
>Manufacturing Systems Integration Division
>100 Bureau Drive, Stop 8263                Tel: +1 301-975-3528
>Gaithersburg, MD 20899-8263                FAX: +1 301-975-4694
>"The opinions expressed above do not reflect consensus of NIST, 
> and have not been reviewed by any Government authority."
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