Is an ORM tool really necessary for web applications?

[Thierry Lam]

I was reading the book AJAX in action and it mentions using ORM tools
such as PEAR, EZPDO or Metastorage. The ORM is supposed to facilitate
data retrieval. Is everyone out there using one of those ORM tools?

[Tony Marston]

On ORM (Object Relational Mapper) most definitely does NOT facilitate data
retrieval. It is used when the structure within an object is different from
the structure within that part of the relational database with which it
connects, in which case you need a mapper to deal with the differences
between the two structures. If the two structures are identical then you
don't need a mapper because it is redundant.

--
Tony Marston

http://www.tonymarston.net
http://www.radicore.org

"Thierry Lam" <la********@gmail.comwrote in message
news:11**********************@m7g2000cwm.googlegro ups.com...

>I was reading the book AJAX in action and it mentions using ORM tools
such as PEAR, EZPDO or Metastorage. The ORM is supposed to facilitate
data retrieval. Is everyone out there using one of those ORM tools?

[Manuel Lemos]

Hello,

on 09/22/2006 04:23 PM Thierry Lam said the following:

I was reading the book AJAX in action and it mentions using ORM tools
such as PEAR, EZPDO or Metastorage. The ORM is supposed to facilitate
data retrieval. Is everyone out there using one of those ORM tools?

I am, but I am suspicious, as I wrote Metastorage. ;-)

Anyway, what can I tell you is that I started Metastorage in 2002 and I
wish I started invested time on it much sooner.

It is really a breeze. I use the Use Case Mapping methodology to develop
Web applications.

http://www.meta-language.net/metastorage-example.html

This methodology could be implemented without using ORM tools, but with
Metastorage now I focus most of my time on implementing the business
logic, i.e. classes that implement the use case logic steps. The data
access layer is totally generated by Metastorage.

Not only it generates bug free code (saving me a lot of debugging time),
but it also prevents that I waste time rewriting data access code
whenever I figure I need to change anything in the data model. Sound too
good to be true, but it is real.

I believe that most people still hand code their SQL. I think that is
due to the fact that they don't know the power of code generation tools
to implement ORM.

At least with Metastorage, you do not have to write a single line of
SQL. You just need to determine what objects of your data model you want
to access and how. If you are confortable with object oriented
programming, it is a matter of time until you get up and running with
ORM tools that do most of the muscle work for you, so you can focus
mostly on the brain work.

--

Regards,
Manuel Lemos

Metastorage - Data object relational mapping layer generator
http://www.metastorage.net/

PHP Classes - Free ready to use OOP components written in PHP
http://www.phpclasses.org/

[Manuel Lemos]

Hello,

on 09/22/2006 08:41 PM Tony Marston said the following:

On ORM (Object Relational Mapper) most definitely does NOT facilitate data
retrieval. It is used when the structure within an object is different from
the structure within that part of the relational database with which it
connects, in which case you need a mapper to deal with the differences
between the two structures. If the two structures are identical then you
don't need a mapper because it is redundant.

That is really not the role of Object Relational Mapping. In this
context, mapping means translating data structures into SQL statements
to store and retrieve such structures from objects.

--

Regards,
Manuel Lemos

Metastorage - Data object relational mapping layer generator
http://www.metastorage.net/

PHP Classes - Free ready to use OOP components written in PHP
http://www.phpclasses.org/

[Tony Marston]

"Manuel Lemos" <ml****@acm.orgwrote in message
news:ef**********@emma.aioe.org...

Hello,

on 09/22/2006 08:41 PM Tony Marston said the following:

>On ORM (Object Relational Mapper) most definitely does NOT facilitate
data
retrieval. It is used when the structure within an object is different
from
the structure within that part of the relational database with which it
connects, in which case you need a mapper to deal with the differences
between the two structures. If the two structures are identical then you
don't need a mapper because it is redundant.

That is really not the role of Object Relational Mapping. In this
context, mapping means translating data structures into SQL statements
to store and retrieve such structures from objects.

I disagree. The primary function of an ORM is not to generate SQL
statements, that is what a Data Access Object is for. An ORM has a different
purpose which I have already explained. Take a look at
http://www.martinfowler.com/eaaCatal...taMapping.html

--
Tony Marston
http://www.tonymarston.net
http://www.radicore.org

[Manuel Lemos]

Hello,

on 09/29/2006 05:41 AM Tony Marston said the following:

>>On ORM (Object Relational Mapper) most definitely does NOT facilitate
data
retrieval. It is used when the structure within an object is different
from
the structure within that part of the relational database with which it
connects, in which case you need a mapper to deal with the differences
between the two structures. If the two structures are identical then you
don't need a mapper because it is redundant.

That is really not the role of Object Relational Mapping. In this
context, mapping means translating data structures into SQL statements
to store and retrieve such structures from objects.

I disagree. The primary function of an ORM is not to generate SQL
statements, that is what a Data Access Object is for. An ORM has a different
purpose which I have already explained. Take a look at
http://www.martinfowler.com/eaaCatal...taMapping.html

I am afraid you are confusion the purpose with the means. This is what
ORM is:

http://en.wikipedia.org/wiki/Object-relational_mapping

Now, how do you implement it, that is another story.

--

Regards,
Manuel Lemos

Metastorage - Data object relational mapping layer generator
http://www.metastorage.net/

PHP Classes - Free ready to use OOP components written in PHP
http://www.phpclasses.org/

[Tony Marston]

"Manuel Lemos" <ml****@acm.orgwrote in message
news:ef**********@emma.aioe.org...

Hello,

on 09/29/2006 05:41 AM Tony Marston said the following:

>>>On ORM (Object Relational Mapper) most definitely does NOT facilitate
data
retrieval. It is used when the structure within an object is different
from
the structure within that part of the relational database with which it
connects, in which case you need a mapper to deal with the differences
between the two structures. If the two structures are identical then
you
don't need a mapper because it is redundant.
That is really not the role of Object Relational Mapping. In this
context, mapping means translating data structures into SQL statements
to store and retrieve such structures from objects.

I disagree. The primary function of an ORM is not to generate SQL
statements, that is what a Data Access Object is for. An ORM has a
different
purpose which I have already explained. Take a look at
http://www.martinfowler.com/eaaCatal...taMapping.html

I am afraid you are confusion the purpose with the means. This is what
ORM is:

http://en.wikipedia.org/wiki/Object-relational_mapping

Now, how do you implement it, that is another story.

The examples in that article clearly show that when the structure of the
object is different from the structure of the database then it because
necessary to provide something which provides a map between the two
different structures. That is entirely different from a Data Access Object
which accesses the database without dealing with different structures. In
short, an ORM is not a DAO, and it is more efficient not to have different
structures so that you do not need an ORM.

--
Tony Marston

http://www.tonymarston.net
http://www.radicore.org

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