Re: Navigation question

From: Walt <wamitty_at_verizon.net>
Date: Tue, 27 Feb 2007 14:58:30 GMT
Message-ID: <qGXEh.30368$kr6.1303@trndny09>

"dawn" <dawnwolthuis_at_gmail.com> wrote in message news:1172534823.070193.104950_at_k78g2000cwa.googlegroups.com...
> Walt wrote:
> > "dawn" <dawnwolthuis_at_gmail.com> wrote in message
> > news:1172505529.681070.131640_at_q2g2000cwa.googlegroups.com...
> > > On Feb 26, 8:28 am, "Walt" <wami..._at_verizon.net> wrote:
> > > > "dawn" <dawnwolth..._at_gmail.com> wrote in message
> > > >
> > > > news:1172444333.974143.227280_at_q2g2000cwa.googlegroups.com...
> > > >
> > > > > On Feb 23, 10:10 am, "Walt" <wami..._at_verizon.net> wrote:
> > > > > > "dawn" <dawnwolth..._at_gmail.com> wrote in message
> > > > > ><snip> My questions are regarding
> > > > > > > layer 7, where "logical navigation" of a database might take
> > place.
> > > > > > > Does that work for you? --dawn
> > > >
> > > > > > what do you mean by "OSI layers?" Are you talking about layers
of
> > > > > > protocols?
> > > >
> > > > > First, I'll grant that the OSI layers are not in my area of
expertise,
> > > > > so I might very well have this wrong. I am talking specifically
of
> > > > > the 7 layers (of protocols) identified as the "OSI layers."
> > > >
> > > > Could you list the layers, and give a link to a web page that
describes
> > > > them?
> > >
> > > I just did a google and I'm not sure whether you had trouble finding a
> > > link or if this is a test to see which link I would choose. We can
> > > start with http://en.wikipedia.org/wiki/OSI_model
> >
> > I know how to google. I wanted to see what page you were reading from,
so
> > that we could read from the same page.

>

> Perhaps I should have been reading from a page.

>

> > The page you pointed me to is a good starting place. So you are talking
> > about protocols.

>

> No, I'm talking about layers and not specifically about the interfaces
> between them (protocols). I'm talking about that which takes place
> within the application layer, using the OSI terminology only to try to
> get the focus within the app layer, rather than below it. If the use
> of the OSI layers was distracting, then simply zero in on application
> software development, including all software (code, metadata,
> database, DBMS specs of any kind) that run or serve as input to
> executables running on top of an OS, for example.

>


> > >

> > > If I had been quizzed, I would have gotten the top, the bottom, and a

> > > few others by name, but I have never studied nor memorized these

> > > layers.  I only referred to them in order to get the focus of the

> > > question on the application layer.

> > >

> > > > > Given
> > > > > these 7 layers, I am not then talking about taking any one of
these
> > > > > layers and further subdividiing it by protocol, but simply
referring
> > > > > to it so that it is clear (that obviously did not work) that I'm
> > > > > talking about the Application Layer.
> > > >
> > > > > > If so, it seems to me that application to
> > > > > > database theory is limited to the areas where data is exchanged
in
> > some
> > > > sort
> > > > > > of formal protocol.
> > > >
> > > > > Surely not.
> >
> > I don't understand the above. "Surely not" what? Do you mean "Surely
not
> > limited to areas where data is exchanged in some sort of formal
protocol"?
> > If that's the case, why did you refer to "the OSI Layers"?

>

> I hope I explained that satisfactorily. Since it is getting in the
> way, rather than helping, ignore OSI and focus on application software
> and the development thereof, including specification for and
> instructions to a DBMS, for example.

>


> >  Database theory is highly relevant to conceptual

> > > > > modeling, outside of this list of 7 layers, as well as to the
> > > > > interface between developer and DBMS, for example. While there
are
> > > > > surely some here who have an interest in data in some
machine-readable
> > > > > format that might not be all that useful for human eyes or
application
> > > > > programmers, I'm interested in Layer 7, the Application Layer.
Again,
> > > > > I am not bringing this in so that we can discuss protocols within
that
> > > > > layer, simply so that it is clear I'm not talking about "physical
> > > > > navigation."
> >
> > If you are not talking about protocols, then why are the OSI layers
> > relevant to your discussion?
> >
> > I'm terribly confused by what you have written.
> >
> > > strictly DBMS navigation). BTW, I didn't mention Pascal. I included
> > > JOG as the third.
> > >
> >
> > Noted.
> >
> > > > Any navigation a programmer
> > > > does entirely within the application is not relevant to the comments
> > Cdd,
> > > > Date, and Pascal have made regarding database data.
> > >
> > > Really? I thought they were opposed to "database navigation" in
> > > general, whether the application is navigating its way through the
> > > data or the DBMS is, or some combination. Hmmm. Perhaps one
> > > difficulty with the terms is that I consider DBMS specifications
> > > related to any application suite to be "part of" that application
> > > suite.
> > >

>

> Did this clarify at all? Thanks. --dawn
>

It clarified a little, but I'm still confused. You can in fact divide things into "layers" without regard to protocols, and the phrase "application layer" means something to me. However, your reference to the OSI layers suggested a common interpretation (between you and me) of the term "application layer", and you are using the phrase to convey something a little different than the OSI people intended.

Let's distinguish between "database data" and "application data". Data can exist in a database, in "working storage" (to use an old COBOL term), and be exchange across the interface.

Whether you navigate in working storage or not is entirely beside the point that Codd, Date, and JOG have made, if I understand that point at all. The point about user navigation interfering with both independence and optimization within the DBMS is about the navigation of database data.

And, just in case, "database data" does *not* refer to copies of database data in working storage. Received on Tue Feb 27 2007 - 08:58:30 CST