Hi Rainer,
> More generally speaking, I am wondering whether you start redoing SDO
here to some extent.
The idea to express JPA metamodel as XML schema is to facilitate
domain-invariant representation of persistent object graphs.
SDO, as I understand, provides a domain-specific schema. Does not have
explicit notions of id or version (that may have changed in newer
versions).
Such a schema will help
a) development of generic (as opposed to domain-specific) browser or
query builder.
and b) data exchange
especially for non-Java clients.
Other use case for such schema is REST based access to data, a topic
which is gathering lot of interest in many quarters.
I am *not* suggesting that a JPA provider provides facility to
externalize the persistent object state. The XML schema exists for those
who wants to build generic services on top of JPA.
The exact form of XSD (or its correctness as in the referred draft)
perhaps is pre-mature at this stage. So I will not elaborate on that.
Except, that the XML schema takes a middle path to express JPA domain -
i.e. it will have notions of id/version/lob etc. and a representation for
persistent reference (CORBA IOR, anyone?).
Regards --
Pinaki Poddar
From: "Rainer Kwesi Schweigkoffer" <kwesi_at_sap.com>
To: Pinaki Poddar/Dallas/IBM_at_IBMUS, jsr338-experts_at_jpa-spec.java.net
Date: 05/25/11 01:24 AM
Subject: XSD (was Re: [jsr338-experts] Re: JPA 2.1 specification
draft)
Pinaki Poddar, am 24 May 2011 hast Du um 11:07 zum Thema "[jsr338-experts]
Re: JPA 2.1 specification draft" geschrieben :
> [1] http://openjpa.apache.org/jest-representation.html
Hi Pinaki,
actually I am a bit confused by the example given on the web page. In
the example I would have expected a uri element to be present within
the instances element (due to minOccurs=1) and the element singular to
be replaced by many-to-one at its first and by one-one at its second
appearance. Also, in the definition of singular-attr-type, to me, there
seems something like <xsd:element name="instance" type="instance-type">
to be missing within the choice. Or was the first singular meant to be
an embedded instead ?
More generally speaking, I am wondering whether you start redoing SDO
here to some extent. (One begins thinking of serialising the metamodel
of a persistence unit to an xsd and its entities to an xml following
that xsd; if we extend the metamodel by OR mapping information...).
Best regards
Rainer
---
Rainer Schweigkoffer SAP AG Walldorf
Business Solution & Technology TD Core JS&I
Technology Development Dietmar-Hopp-Allee 16
Java Server Core D-69190 Walldorf
JEE Implementation Group phone: +49 6227 7 45305
Building 3, I.3.14 fax: +49 6227 7 821177
rainer.schweigkoffer_at_sap.com
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