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Subject: [OASIS Issue Tracker] Updated: (ODATA-165) Support Cross-joins

     [ http://tools.oasis-open.org/issues/browse/ODATA-165?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Stefan Drees updated ODATA-165:

Advanced clients MAY request cross-joins, i.e. posing queries (based on other join conditions, with $expand for the entity sets to be joined, and add $filter to specify the equivalent of the join condition) in the case where the spanning entity sets are not all related by an association . 
To enable this potentially useful capability, the server SHOULD allow requests to be rooted at the entity container, and in doing so the latter MUST either provide explicit navigation properties in the model (i.e. where useful navigations exist) or MUST define implicit navigation properties with cardinality "to one" to each entity set (and potentially each function) it contains, so that queries across entity sets could be supported by referring to properties qualified by entity set. 
In any of the two cases, the entity container SHOULD be annotated in the same way as entity sets to express which aggregate queries are supported. 

(For an example please see inside comments.)

As discussed in meeting#30 2013-03-21 copied proposal from comment to proposal field

> Support Cross-joins
> -------------------
>                 Key: ODATA-165
>                 URL: http://tools.oasis-open.org/issues/browse/ODATA-165
>             Project: OASIS Open Data Protocol (OData) TC
>          Issue Type: Bug
>          Components: OData Protocol 
>    Affects Versions: V4.0_WD01
>         Environment: [Proposed]
>            Reporter: Michael Pizzo
>            Assignee: Michael Pizzo
>             Fix For: V4.0_WD01
> We often have requests to support queries that span entitysets. Where navigation properties exist between the entitysets these provide a natural and convenient mechanism for building queries that span entitysets. However, where navigation properties are not present a way is needed to build such cross-entity spanning queries.
> In the context of looking at aggregation we came up with a solution for doing this by considering the entitycontainer as the cross-product of the contained entitysets. You could then $expand the entitysets you wanted to join, and add a filter to specify the equivalent of the join condition. This seemed generally useful beyond just the scope of aggregation.

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