There are several petterns for persistent object, which is distinguished by using object / relational database mapper (O/R mapper) or not. All the petterns are designed to abstract database transaction and to standardise the method without coding around difference behavior of each database. Some programming languages have standard API for persistence, eg. Java Persistence Interface, Perl DBI.
I introduce some of the petterns for discussion of the openEHR persistence API. This section will be change frequently because I am now studying about these pattern for implementation on Ruby. Please point out and comment me, if you find my mistake.
1. Domain Logic pettern
This model has layers like openEHR, such as Service layer, Transaction script, Domain model and Table module. This model is well abstracted enough to standardise database access method, if it is OODB, RDBMS, XMLDB or others. Otherwise the implementation will be difficult because this model has some complexity about relationship of classes.
2. Data source architectural pattern
This pattern has simple gateway for DBMS. But this method is mainly target to RDBMS.
Refferences
1. Martin Fowler, Patterns of Enterprise Application Architecture, 2002