Date, the relational model and the application (software layer)

Initially this would seem understandable, from the historical perspective because of the evolution of the architecture of software layers over and above the hardware layer (E0):

Software environment E1: machine and network operating system software
Software environment E2: (R)DBM system software
Software environment E3: database application system software

Question 1:
Discussion of the relational model (RM) seems to suggest to me that Date (and
others) envisage that the RM is to be implemented in environment E2 (ie: as some advanced form of RDBMS software). Do you consider this to be a correct statement, and if not, why?

Question 2:
I cannot conceive of a production realtime database system without the sybiosis of each of these above 3 system software layers (E1, E2, E3), yet the database theory promulgated by Date appears to ignore any reference to the application. Do you consider this to be a correct statement, and if not, why?

Question 3:
In recent years there has been an increasing tendency to migrate "code" from the application software environment E3 to the RDBMS software environment E2. Examples of this evolving tendency include the use of database constraints, triggers, but are dramatically highlighted by the utility of RDBMS stored procedures. (eg: this code may have been previously physically held external to the DBMS on the client app E3).

Date does not seem to address this (evolving) issue ... How does the relational model interface the application software environment?

Question 4:
It is quite understandable that the RM be considered to be entirely independent of the application to which the model is to be applied, for this is its strength. However, OTOH, according to my position developed above, whenever the RM will be implemented in some form of RDBMS it will be implemented with a very real application software layer which will be physically interfaced from the RDBMS software layer. This appears to be a database systems management issue (or aspect thereof) that is not in the realm of database theory. Is this correct?

Question 5:
The above 3 software layers might be physically and logically separate however they must be managed at an implementation concurrently. The end database systems solution thus appears as an evolving symbiosis of these 3 different software environments. Is this a reasonable statement?

Any references to Date's work on any of these questions would be appreciated. Received on Thu Mar 11 2004 - 23:49:42 CET