Re: dbdebunk 'Quote of Week' comment


"Alexandr Savinov" <spam@xxxxxxxxxxxxxxxxxxx> wrote in message
news:430efd5d$1@xxxxxxxxxxxxxx
> x schrieb:
> > This means that there must be a one to one mapping between the generated
key
> > and some key with a meaning for the end user. Therefore that meaningless
> > primary key is a pointer. But one of the goals of the relational model
is to
> > eliminate pointers from the data model.

> What is the difference between meaningless and meaningful pointer?

If the key is meaningful for the end-user, it is not a pointer.

> I think the model itself does not know anything about the meaning of the
> pointers/keys it uses. In this sense the question about the meaning of
> pointers/keys relates to data modeling in general rather than to the RM.

> In other words, the question is if we should choose meaningful or
> meaningless identifiers for our entites.

If they are meaningless, they are not identifiers.

> > Other goal is to give the end user direct access to data.

> Any access is indirect (by definition). By direct access we normally
> mean some lower level mechanism of access w.r.t. this level.
> (Absolutely) direct access does not exist just like instant interaction
> does not exist. Possibly you mean an illusion of direct access like in
> OOP where we manipulate object like if they were directly accessible.

Direct access as in access to data by standard tools, not by specialized
applications.


.

Relevant Pages

  • Re: Simple question, err... I think
    ... It's meaningless to then direct me to look at the code. ... quality of the code it felt safe to assume a leak :-)). ... Set B(Set l, int n, Set r) ... /All/ 'return' statements in this function return a pointer to a freshly ...
    (comp.programming)
  • Re: Question about void pointers
    ... that constitute an arbitrary object: ... also why I find it more natural to use void *: ... Fundamentally, the meaning of p+3, when p is a non-null pointer to an object type, is that *refers to an object of the pointed-at type which is three objects of that type forward from the object referred to by *p. ... That meaning disappears when *p itself is meaningless, which is why the standard forbids pointer arithmetic on void* pointers. ...
    (comp.lang.c)
  • Re: printf("%d",float)
    ... cast the address of a float into the address of an int. ... The result of casting a pointer to an object or incomplete to ... Of course, dereferencing that pointer ... which is why I consider the conversion meaningless. ...
    (comp.lang.c)
  • [PATCH 54/64] mips: remove driver_data direct access of struct device
    ... the driver core is going to not allow direct access ... to the driver_data pointer in struct device. ...
    (Linux-Kernel)
  • Re: Passing a constant by reference
    ... A constant expression has no address; what you're asking for is meaningless. ... Storage locations produce addresses, not constant values. ... This will then most likely produce an access violation upon access, since "5" is rarely a valid address, but if the "void*" is meant to merely hold a pointer-sized value rather than an actual pointer, this might have some meaning. ...
    (microsoft.public.dotnet.languages.vc)
Quantcast