DAL means (to me) a layer that talks to a specific RDBMS (or any DataStore),
and returns certain type objects (not rdbms specific) to the business layer.
I think of a DAL returning:
DataSets (strong or weak, but usually strong)
IDataReaders
void (just run something, but return nothing)
int ( counts, number of rows affected, etc)
If you have a function like this
public IDataReader GetEmployees()
{
return something.ExecuteReader();
}
Then the code inside that method can be specific. ( it can return sql
server, oracle, access, excel, text file, etc).
THEN, when you're biz layer used the IDataReader, it can put the data into
objects.
.........
Because you return an IDataReader, today, it can be Sql Server, tomorrow,
Oracle.
See my full example at:
http://sholliday.spaces.live.com/Blog/cns!A68482B9628A842A!140.entry
"Peter" <Pe***@discussions.microsoft.comwrote in message
news:DD**********************************@microsof t.com...
I'm confused about Data Access Layer and Data Object Layer. How are they
related? Which layer will be affected when the underlying database
structure
is changed? Which layer will be affect when additonal information (more
columns and/or from more tables) from the database is needed?