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Re: Linked Data with web2py

From: Kingsley Idehen <kidehen@openlinksw.com>
Date: Thu, 24 Dec 2009 10:30:02 -0500
Message-ID: <4B3388FA.1010908@openlinksw.com>
To: Massimo Di Pierro <MDiPierro@cs.depaul.edu>
CC: "public-lod@w3.org" <public-lod@w3.org>, Chris Baron <topher.baron@gmail.com>
Massimo Di Pierro wrote:
> Hi Kingsley,
>
> Internally we use the Python ODBC driver for the connection to DB2 and 
> to MSSQL.
But how have you come to conclude that ODBC only works with DB2 and 
MSSQL? What about ODBC Drivers that have been developed to work 
consistently across:

Virtuoso, Oracle, SQL Server, DB2, Informix, Ingres, Sybase, Progress, 
MySQL, Firebird, other ODBC Drivers, JDBC Drivers etc? Thus, you could 
have the option ODBC as opposed to: ODBC for DB2 and MS SQL Sever.

What about the fact that you have ODBC Drivers for Virtuoso that enable 
to make one ODBC connection to all the DBMS engines above, and treat 
their tables as though they were part of one DBMS i.e., Virtual DBMS 
based Relational Data Virtualization (or Federation).

> We use more specific drivers for the other databases, as recommended 
> by the official documentation. 
What official documentation? URL please.
> Anyway, from the Python programming point of view they all expose the 
> same Python API.
>
> The fact is ODBC only unifies the data access API and that is a small 
> part of we needed since different database still have different dialects.
> Our DAL completely abstracts the database and writes the SQL in the 
> specific dialect of specific backend.
Are you aware of the fact that via ODBC metadata calls you can 
deductively discern the capabilities and SQL dialiects supported by an 
DBMS. This is all about the ODBC Drivers you are working with, not the 
ODBC spec itself (which is vast and very sophisticated).
>
> For example a limit query in SQLite is done with "SELECT ...  FIRST N" 
> The same query in MSSQL is done with "SELECT .... TOP N", in Oracle it 
> requires two nested selects "SELECT ... FROM (SELECT w_tmp.*, ROWNUM 
> w_row FROM (SELECT ...) w_tmp WHERE ROWNUM<=N)...;".  In the case of 
> the Google App Engine there is not even SQL so our DAL translates 
> directly into Google API calls.
Again, you should focus on the functionality you want, and then see if 
the underling ODBC Driver can handle what you want, if it can't you can 
drop back to your work arounds.

>
> The same query in the web2py DAL reads like, for example:
>
>     db=DAL('postgresql://username:password@localhost', pool_size=100)
>     db.define_table('person',Field('name'))
>     db.person.insert(name='Ken')
>     rows = db(db.person.name=='Ken').select(limitby = (0,10))
>
> The first line choose the most appropriate connection driver (which 
> may be ODBC). The second line tried to define a table "person". If it 
> does not exist, it is CREATEd. If it exists and has a different 
> stricture, it is ALTERed. The third line inserts a second. The forth 
> line is performs the limit query.
>
> As you can see we do not use raw SQL anywhere in our system, although 
> our system may use SQL to talk to the database. Using raw SQL also 
> presents the disadvantage that, if one is not very careful in escaping 
> variables, one may introduce SQL Injections vulnerabilities. We do not 
> have to worry about that with the DAL.
I do understand the abstraction.
I worked with a product called DAL [1] for Mac OS Classic in the early 
1990's  (and others pre ODBC, which arrived in 1992 as Windows port of 
what was then the SAG CLI) :-)
>
> The RDF tagging is done at the DAL level:
>
>     db.person.name.rdf = { .... }
>
> Anyway, it is possible there is some feature of ODBC that we have 
> overlooked and we may be able to take  advantage of.
Yes.

You have ODBC itself. Then you have Virtuoso VDBMS (think scalable high 
performance variant of Microsoft Access JET Engine which major benefits).


Kingsley
>
> Massimo
>
> On Dec 24, 2009, at 6:57 AM, Kingsley Idehen wrote:
>
>> Massimo Di Pierro wrote:
>>> Hello everybody,
>>>
>>> I am a new member of this list and first of all I wish everybody Happy
>>> Holidays.
>>>
>>> I also take the occasion to introduce the RDF plugin for web2py.
>>>
>>>    http://web2py.com/semantic
>>>
>>> web2py is an Open Source web framework for rapid application
>>> development written in Python and programmable in Python. web2py runs
>>> almost everywhere and includes everything you need for web development
>>> in one package including a ssl-enabled web server, a transaction-safe
>>> relational database, a web-based IDE, a web-based database
>>> administration tool, and a Database Abstraction Layer that writes SQL
>>> for you and works transparently on SQLite, MySQL, Postgresql, Oracle,
>>> MSSQL, FireBird, DB2, Informix, Ingres, and on Google App Engine.
>>>
>>> Web2py requires no installation: just download, unzip and click to
>>> start it.
>>> You can see an online demo here:
>>>
>>>   http://web2py.com/demo_admin
>>>
>>> The RDF plugin allows to label (tag) database fields and relations
>>> with ontologies and web2py automatically exposes the data in the
>>> database as Linked Data via a RESTful web service. Works with all
>>> database back-ends listed above.
>>>
>>> Any comment and feedback will be appreciated.
>> Any reason why you don't use ODBC for your data access? Your references
>> above imply you implemented data access APIs on a DBMS by DBMS basis.
>> ODBC is not only superior to all Native DBMS APIs, it is generic thereby
>> shrinking you development and maintenance costs.
>>
>> Kingsley
>>>
>>> Massimo
>>>
>>> -------------------------------------------------------
>>> Massimo Di Pierro
>>> Associate Professor
>>> School of Computing and Digital Media
>>> DePaul University
>>> 243 S Wabash Ave
>>> Chicago IL 60604
>>> +1-312-375-6536 (phone)
>>> +1-312-375-6116 (fax)
>>>
>>>
>>>
>>>
>>
>>
>> -- 
>>
>>
>> Regards,
>>
>> Kingsley Idehen          Weblog: http://www.openlinksw.com/blog/~kidehen
>> President & CEO
>> OpenLink Software     Web: http://www.openlinksw.com
>>
>>
>>
>>
>
>


-- 


Regards,

Kingsley Idehen	      Weblog: http://www.openlinksw.com/blog/~kidehen
President & CEO 
OpenLink Software     Web: http://www.openlinksw.com
Received on Thursday, 24 December 2009 15:30:35 GMT

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