[ontoiop-forum] OMS: Structured focused basic distributed query

[Tara Athan]

On 9/19/14 10:20 AM, Till Mossakowski wrote:
> Dear Tara,
>
> Am 11.09.2014 17:14, schrieb Tara Athan:
>> * I am confused about the term "structured OMS". The glossary 
>> definition of structured OMS is
>>
>> \termdefinition{structured OMS\synonym focused OMS}
>> {\termref{OMS} that results from other \termref{OMS} by 
>> \termref{import}, \termref{union}, \termref{combination}, 
>> \termref{renaming} or other structuring operations}
>> \begin{note}
>> The term ``focused OMS'' emphasizes the fact that the OMS, while possibly
>> involving many OMS as parts, has a single resulting \termref{logical 
>> theory}.
>> This is in contrast to \termref{distributed OMS}, which do not have
>> such a unique result, but rather comprise a network of OMS and
>> \termref{mappings}. See \cite{MossakowskiTarlecki09}.
>> \end{note}
>>
>> As I read this, a basic OMS cannot be structured OMS - it is not the 
>> result of a structuring operation applied to another OMS.
>>
>> Elsewhere, the phrase "sentence or structured OMS" is used, 
>> suggesting that it is considered a structuring operation when a 
>> number of sentences are joined together in a basic OMS, so that a 
>> basic OMS would be a structured OMS.
>>
>> It seems more natural to me that structured and basic OMS would be a 
>> disjoint partition of OMS. All OMS languages that I know have an 
>> internal operation for jointly asserting sentences as a logical 
>> theory, while the other kinds of structuring operations are not 
>> universal.
>>
> OK, agreed.
>
>> * If the term "distributed OMS" is replaced by "OMS network", then 
>> the question arises as to what OMS are not focused.
> I would keep "distributed OMS" as a synonym for "OMS network".
>>
>> The current definition of OMS is
>>
>> {set of expressions (like \termref{non-logical symbols}, 
>> \termref{sentences} and \termref{structuring} elements) in a given 
>> \termref{OMS language} (or several such languages)}%
>>
>> I think it would better to define OMS as a 'collection' of 
>> expressions rather than a set. Saying something 'is a' set does not 
>> leave room for additional structure.
>>
>> So here's my proposal
>>
>> \termdefinition{OMS}
>> {collection of expressions (like \termref{non-logical symbols}, 
>> \termref{sentences} and \termref{structuring} elements) in a given 
>> \termref{OMS language} (or several such languages).}
>>
>> \termdefinition{focused OMS}
>> {\termref{OMS} that has a single resulting \termref{logical theory}.}
>>
>> \termdefinition{structured OMS}
>> {\termref{OMS} that results from other \termref{OMS} by 
>> \termref{import}, \termref{union}, \termref{combination}, 
>> \termref{renaming} or other structuring operations}
>> \begin{note}
>> An OMS is either a basic or structured OMS.
>> \end{note}
> agreed, except that I prefer to say "A *focused* OMS is either a basic 
> or structured OMS."
>> Finally, I see that the present approach is to consider queries as a 
>> subclass of OMSs. It is unclear to me how the inclusion of a query 
>> into a structured and focused OMS would affect the "single resulting 
>> logical theory".
>>
>> Does it make sense to consider a query as an OMS, but not a focused 
>> OMS, which could be a component of a structured OMS (which would then 
>> also be not focused?
>
> currently, queries are part of OMS networks (= distributed OMS).
> I cannot see why they should become part of structured OMS. How would 
> they then affect the model class of the structuted OMS?
This comes back to what is the defining concept for the term "structured 
OMS".  The name suggests it is simply an OMS with structure (whatever 
that means). There is, I imagine, some category-theoretical way to 
distinguish a structure from a network.

Given that we are now allowing OMS which are simply queries, then it 
seems reasonable to me that there could also be queries with structure, 
or hybrid assertion-query OMS with structure.

Here are some use cases, where the relationship between the components 
seem to me to be tighter than what I would expect in an 'OMS network':
1. It is not uncommon to have a set of queries.
For example if a query language does not support disjunction, then this 
may be emulated by applying two queries and taking the 'union' of the 
results.

2. In certain query languages, query results can depend on the order of 
application, so a sequence of queries is a relevant construct.

3. Translation between query languages is a reasonable operation to support.

4. I can certainly imagine forming a combination query using multiple 
query languages, dependent on a translation between the query languages.

5. Query rewriting is a technique developed in the database world that 
may be relevant for querying structured OMS, and, somewhat out of scope 
for OntoIOp, is important for supporting OBDA.

6. There are a number of languages, especially in the LP realm, that 
allow assertions (and other performatives that modify the theory, such 
as retractions) to be interlaced with queries.

Tara
>
> Best, Till
>
>> Tara
>>
>>
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