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Subject: Key Concept from a DAS point of view

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.



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
71 Rue Desnouettes
75015 Paris


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 services.



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