Hi all,
Here are the main points of yesterday’s
Key Concept presentation.
First of all Keys are a very important
concept from a DAS point of view because they uniquely identify objects stored
in the underlying datasources.
The statement above leads to define an
identity concept with a bigger scope than a simple data graph.
When talking about DAS Keys there are two
things to distinguish:
1. How
to tell to the DAS what are keys for business Types (configuration)?
2. How
a client can get Keys metadata from a DAS?
For instance the DAS group decided to let
the item “1” to the implementation.
So only the second point will be specified
which means that the only contract that should be respected by a DAS is to be
able to return the Key Types metadata.
Then having Keys in SDO targets the first
point.
DAS should not rely on SDO Keys definition
but can use it as a possible input because we can imagine that future DAS
versions could work independently from SDO.
Definitions:
Key is the global concept, it represents
the complete identity of a DataObject
Key is composed of one or more Key Elements
which allows supporting the “compound keys” concept.
A key element is an SDO property
·
It must be a “many=false”
property.
·
It can be a DataType property
·
It can be a DataObject property
o The decision to support both “containment” and “non
containment” is still open.
o If a Type B participates in the key of Type A (A has a property of
type B) then all key elements of B participate in the key of A.
It means that the Key of A cannot contain a subset of B’s key elements
Key Elements value initialization is an
additional level of metadata for Keys which is a DAS specific one (IMO)
·
user provided
·
DAS/datasource generated
Finally what the DAS group expects from the
SDO group is:
·
To do not define concepts
conflicting with the definitions above
·
Being able to use SDO Keys as a
possible configuration source for DAS.
·
To Provide an improved XML
serialization format of the ChangeSummary (maybe based on Keys)
I will be pleased to give more
details/explanations…
Best Regards,
Christophe
Boutard
R&D
Team Leader
Phone: +33 1 78 42 35 37
Fax: +33 1 77 72 56 47
christophe.boutard@xcalia.com
71
Rue Desnouettes
75015 Paris
www.xcalia.com
Xcalia
provides intermediation software for the agile enterprise to easily create
transactional composite applications. Using metadata and dynamic composition,
intermediation enables consistent, configurable and unified access to data and
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