Date: Wed, 23 Jul 2008 02:03:27 -0700 (PDT)
On Jul 23, 12:44 pm, "Brian Selzer" <br..._at_selzer-software.com> wrote:
> > A symbol is already defined as "something used for or regarded as
> > representing something else".
> Yet symbols are not values.
When one says false is a value, one is referring to the abstract boolean value of false. When one says false is a symbol one is referring to its use as an identifier within a sentence. Both usages are common.
Only sentences contain symbols and conversely sentences only contain symbols (ie not the values that they represent). However within a sentence we normally interpret a symbol as standing for the value it is deemed to represent and not the symbol itself.
In the RM formalism, relations are defined as abstract sets of tuples, and tuples are formalised as mappings from attribute names to attribute values. Relations are not sentences on some grammar and therefore are not composed from symbols.
In a database encoding there is only a single defined interpretation of the encoded attributes as values in the RM formalism. Therefore there is no distinction between symbol and value that can be made. For example the integer value 42 may be represented using a little endian encoding in memory where we ultimately need to know how to interpret voltage levels, address lines, data lines and so on. Even though an underlying binary representation can be seen as a symbol composed of 1ís and 0ís in some language it is as irrelevant an implementation detail as the choice of voltage level or address line conventions to the RM formalism. Received on Wed Jul 23 2008 - 04:03:27 CDT