Persistence & DBMS
Relationship of objects to tables
Objects & attributes v rows & columns
Multi-valued attributes & joins
Persistence adds no semantic value
Same for file, ISAM & object DBMS
SQL interface can be automated
Notes:
Business objects typically persist between sessions.
They are also used by multiple concurrent users in most situations.
Database technology may be used to provide this persistence.
There is a direct relationship between semantic objects and relational tables.
The objects of a class and its attributes are equivalent to the rows and columns of a table.
Multi-valued attributes are modeled by a separate table which joins to the primary table via an efficient foreign key/primary key join.
Persistence is effectively a scoping mechanism, and add absolutely no additional semantic value.
The choice of persistence mechanism between a stream file, ISAM table, relational database or object database is a technical decision, not a business decision.
The mapping between a business object and underlying persistence mechanism can and should be automated.
This is facilitated by the Java™ Database Connectivity (JDBC) package which has the same interface for relational and ISAM data sources.
JDBC manages connections, transactions and mapping between Java™ and SQL data types.