[OASIS Issue Tracker] (EBXMLMSG-108) Unclear if empty ConversationId is allowed

[OASIS Issues Tracker <workgroup_mailer@lists.oasis-open.org>]

    [ https://issues.oasis-open.org/browse/EBXMLMSG-108?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=67243#comment-67243 ] 

Pim van der Eijk commented on EBXMLMSG-108:
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The ebMS 2.0 schema mandated two headers that users in practice do not always want to use:  the agreement reference (cpa id in v2.0) and the conversation id.    In ebMS3,  the first issue was solved by making AgreementRef optional.   The second unfortunately wasn't.  The agreement ref is still mandatory.  

There is a difference between a message that the sending MSH (or sending user or application) assigns to a conversation and a message that is not part of a conversation,  or constitutes its own conversation.   In ebMS2, the ConversationId had a "non-empty-string" type, so it needed a value.  A few user communities independently adopted the convention to (re)use the message identifier as conversation identifier.  Having a default value "1" as in ebMS3 Core would mean that all messages are part of the "1" conversation unless specified otherwise, which is not the same. 

The ebMS3 schema changed the data type to the "token" type.  The empty string is a valid token.  In ENTSOG AS4, whose users today don't have a conversation concept, the element is profiled to be the empty string to express that the message is not part of an identified conversation.




> Unclear if empty ConversationId is allowed
> ------------------------------------------
>
>                 Key: EBXMLMSG-108
>                 URL: https://issues.oasis-open.org/browse/EBXMLMSG-108
>             Project: OASIS ebXML Messaging Services TC
>          Issue Type: Bug
>          Components: Core Spec
>            Reporter: Sander Fieten
>
> In §5.2.2.6 states that the eb:ConversationId element is required and must occur in the ebMS message header. In §5.2.2.10 where the element is further described it is stated that the value is "a string identifying the set of related messages that make up a conversation between Parties." and "The actual semantics of this value is beyond the scope of this specification.". There is no explicit statement on whether an empty string is allowed.
> The XML schema defines the type of this element as xsd:token without any further restrictions, so an empty string would be valid. It is however unclear whether this is intentional as also the eb:Action element has the same type although the Action shall not be an empty string.
> Because an empty string doesn't really qualify as an identifier it seems logical to assume that an empty value is not allowed here.
> Additionally §4.3 defines also a default value of '1' for this element if no value is specified also suggesting that an empty value is not allowed.



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