Need some clarification on the ANSI/SPARC 3-tier database architecture.
- by Moonshield
Hi there,
I'm currently revising for a databases exam and looking over some past papers, but there's one question that I'm slightly unsure about and was wondering if someone could offer some assistance.
"Describe EACH of the THREE levels of
the ANSI SPARC 3 level architecture.
Your answer should include the purpose
of EACH of the schemas, the level of
abstraction they provide and the
software tools that would be used to
access and support them."
As I understand it (although please correct me if I'm wrong): the internal schema specifies the physical storage of the data; the conceptual schema specifies the structure of the database and the domains; and the external schemas are how the database is viewed by "users" (applications, etc.). As for the abstraction, I understand that the conceptual layer means that the physical data storage can be altered without the end user being affected, likewise the
The bit that I'm not sure about is what tools are used to access and support each layer. Would the internal schema be handled by the DBMS, the conceptual schema handled by some sort of DDL interpreter and the external schema handled by a DML interpreter (or have I misunderstood what each level does)?
Any assistance would be greatly appreciated.
Thanks,
Moonshield
