Re: OO versus RDB
From: J M Davitt <jdavitt_at_aeneas.net>
Date: Thu, 29 Jun 2006 14:00:58 GMT
Message-ID: <u2Rog.1288$u11.1218_at_tornado.ohiordc.rr.com>
>
>
> This particular paragrah of my response was not intended to answer your
> question, but instead to ensure that I had understood the question
> correctly, in particular because a quick google search for 'relational
> algebra operations' shows in the top five result only one, the fifth, that
> actualy refers to this operation as 'restrict'; the others call it
> 'select'. I just wanted to avoid any possible misunderstandings about the
> terminology in use, also because I am coming mainly from the direction of
> being a pragmatic software developer rather than a deep theorist on any
> particular subject. Please also keep this in mind if my use of terminology
> is imprecise or inaccurate - that will probably be because I have lots of
> things to learn.
Date: Thu, 29 Jun 2006 14:00:58 GMT
Message-ID: <u2Rog.1288$u11.1218_at_tornado.ohiordc.rr.com>
Christian Brunschen wrote:
> In article <04Cog.3422$pu3.83147_at_ursa-nb00s0.nbnet.nb.ca>,
> Bob Badour <bbadour_at_pei.sympatico.ca> wrote:
>
>>Christian Brunschen wrote: >> >> >>>In article <eZxog.3346$pu3.80765_at_ursa-nb00s0.nbnet.nb.ca>, >>>Bob Badour <bbadour_at_pei.sympatico.ca> wrote: >>> >>> >>>>Christian Brunschen wrote: >>>> >>>> >>>>>In article <1151501485.755962.108350_at_p79g2000cwp.googlegroups.com>, >>>>>erk <eric.kaun_at_gmail.com> wrote: >>>>> >>>>> >>>>>>topmind wrote: >>>>>> >>>>>> >>>>>>>[...] (Unlike OO, where encapsulation >>>>>>>encourages each object/class to reinvent its own >>>>>>>add/change/delete/cross-reference/search rules and interfaces so that >>>>>>>they are all different for each project or shop. >>>>>> >>>>>>Agreed. I wouldn't have a problem with inconsistencies if the languages >>>>>>just offered some powerful basic operations. You can't even write >>>>>>something in Java like this, which would be completely type-safe: >>>>>> >>>>>>Set<LineItem> items = >>>>>>theOrder.lineItems.where(item.status==Status.SHIPPED); >>>>> >>>>>Perhaps somewhat interestingly, in a dynamic OO language such as >>>>>Smalltalk, Objective-C or Ruby, you can use the technique of Higher-Order >>>>>Messaging (HOM), as described in the 2005 OOPLSA paper >>>>><www.metaobject.com/papers/Higher_Order_Messaging_OOPSLA_2005.pdf>, to do >>>>>something quite similar; in Objective-C syntax something like >>>>> >>>>> NSSet *lineItems = >>>>> [[[[order lineItems] selectWhere] status] equals:STATUS_SHIPPED]; >>>> >>>>You have given an example involving only restriction. >>> >>>If I interpret things correctly, this is what is called 'selection' in >>>some places (suh as <http://en.wikipedia.org/wiki/Generalized_selection> >>>and <http://www.cse.ohio-state.edu/~gurari/course/cse670/cse670Ch4.html>)? >> >>Suggesting a synonym for restrict does not answer my question.
>
>
> This particular paragrah of my response was not intended to answer your
> question, but instead to ensure that I had understood the question
> correctly, in particular because a quick google search for 'relational
> algebra operations' shows in the top five result only one, the fifth, that
> actualy refers to this operation as 'restrict'; the others call it
> 'select'. I just wanted to avoid any possible misunderstandings about the
> terminology in use, also because I am coming mainly from the direction of
> being a pragmatic software developer rather than a deep theorist on any
> particular subject. Please also keep this in mind if my use of terminology
> is imprecise or inaccurate - that will probably be because I have lots of
> things to learn.
[snip] Received on Thu Jun 29 2006 - 16:00:58 CEST