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This document will also outline additional changes that are anticipated in the development of DSpace 7.x.

DSO - DSpace Objects

A DSO is a DSpace Object (Collection, Item, Bitstream).  A DSO is saved to the database.  Bitstreams are a special type of DSO that have binary storage in addition to data in the database.

Each DSO is represented as a table in the DSpace database.  Some additional tables are present to represent relationships between DSOs.

org.dspace.core.Context - DSpace Context

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The Context object can be set to a read only mode for enhanced performance when processing many database objects in a read-only fashion.

Curation Context (Curator.curationContext())

A context object built to be shared between Curation tasks.

Database Interaction (before DSpace 6.x)

All Database actions requires the presence of a Context object.  

All DSOs are constructed with a Context object.  The context object provides access to the database connections to create/retrieve/update/delete DSOs.

The context object is used to authorize access to particular actions.

Data Access Objects (introduced in DSpace 6.x)

The concept of a Data Access Object (DAO) was introduced in DSpace 6 to provide an optimization layer between the DSpace code and the DSpace database.

In DSpace 6, Hibernate was implemented as the DAO.  The DAO concept would allow for a framework other than Hibernate to be implemented in the DSpace code base.

Hibernate (introduced in DSpace 6.x)

DSpace 6 introduced hibernate (http://hibernate.org/orm/) as an object relational mapping layer between the DSpace database and the DSpace code.

Objects accessed by hibernate are registered in the hibernate.cfg.xml file.  DSO properties and relationships can be inferred from the database schema.  Additional relationships can be explicitly declared using Hibernate annotations.