Re: Object-relational impedence
Date: Wed, 5 Mar 2008 01:05:30 -0600
Message-ID: <2008030501053015668-unclebob_at_objectmentorcom>
On 2008-03-03 18:24:33 -0600, Marshall <marshall.spight_at_gmail.com> said:
> One's requirements dictate data with certain functional dependencies.
> Among the easiest tasks in application design is one of the earliest:
> structuring the data. The RM structures data as relations. Relational
> structures lack query bias, which is one of the reasons why SQL
> is so good at ad hoc queries (compared to the other choices.)
> OO structures mandates an object structure (unsurprisingly): out the
> gate, one has no choice but to build in a query bias, whether
> one wants it or not.
Agreed. That "bias" can work very well if you only use the biased
queries. That works well in the context of a single application, or a
single piece of an application. It does not work well in the general
case, which is why OODBs never quite took off.
>
> Furthermore, since OOPLs lack physical independence, traversing
> the graph may be quite expensive, particularly in the case where
> the graph is backed by storage in a database, which is part of
> why ORM is such a universally bad idea.
-- Robert C. Martin (Uncle Bob) | email: unclebob_at_objectmentor.com Object Mentor Inc. | blog: www.butunclebob.com The Agile Transition Experts | web: www.objectmentor.com 800-338-6716 |Received on Wed Mar 05 2008 - 08:05:30 CET