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From "Pinaki Poddar (JIRA)" <>
Subject [jira] Created: (OPENJPA-1686) Persistence of Dynamic and Generic Type
Date Tue, 08 Jun 2010 01:52:10 GMT
Persistence of Dynamic and Generic Type

                 Key: OPENJPA-1686
             Project: OpenJPA
          Issue Type: Bug
            Reporter: Pinaki Poddar
            Assignee: Pinaki Poddar

Persistence of semi-structured data has attracted lot of attention lately -- especially for
web centric applications where flexibility/malleability of data structure trumps the benefits
of strongly-typed, schema-oriented relational database.

OpenJPA as a leading object persistence solution must have a comprehensive story (or may be
epic in Agile nomenclature is more appropriate for this issue) for persistence of semi-structured

This umbrella issue will explore two major aspects of this broad technical problem

a) Mapping semi-structured data to Relational database 
b) Mapping semi-structured data to non-Relational database

Mapping semi-structured data to Relational database:
    OpenJPA has traditionally offered various degree of type support for persistent data --
starting from the decalred persistent type such as @Entity to the weakest namely a serialized
blob. The capability of interest in this regard is the support of the intermediate form between
these extremes where a persistent state/relation can be declared merely as persistce capable
instead of its exact type. This support is also relevant for generic types where the exact
type is only known at run-time instance at design time. 
   OpenJPA documentation and examples of this feature had been thin -- and hence less exeercised.
Moreover, I believe that this support has regressed while introducing numerous new feature
for JPA 2.0. So one aspect of this issue will explore the extent of support for persistence
capable types and document them appropriately.

   A simple and commonly used way to model a dynamic data structure is name-value pair. However,
this simple Java modeling technique has several alternatives to be mapped into a relation
database. One component of this issue will explore 
OpenJPA's support for persisting and querying name-value pairs and document them for future
usage as many forum users have raised technical question or expressed interest in name-value

Mapping semi-structured data to non-Relational database
  The current surge of interest in this area also has revived an ancient discussion -- what
is the applicability/advantage of non-relational data store? Several interesting non-relational
databases such as BigTable, Cassandra, HBase, MongoDB, neo4j had proven their merits and been
widely investigated. OpenJPA is uniquely capable to integrate JPA application model on top
of these non-relational databases. Because OpenJPA architecture cleanly distinguished between
object life cycle management and data store interaction and query expressions (in its early
days -- OpenJPA developed an interface to a object database). The second aspect of this issue
will explore this option by developing a connector to one (or more, if time permits) non-relational


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