question on $targetHomeCommunityIdList parameter

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Andries Hamster

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Sep 22, 2025, 4:18:58 AM (6 days ago) Sep 22
to IHE ITI Technical Committee
Hello,

A while ago we discussed the addition of a new optional parameter to the an ITI-18 and ITI-38 query request call the $targetHomeCommunityIdList. 

Have a question for the group that was involved. What should a responding gateway behavior be if the targetHomeCommunityIdList is part of the query request but empty? 

is that: 
A - ignore the parameter and attempt to provide a response in the same way as when not targetHomeCommunityIdList parameter was included?
B - flag this as an error situation (and return an appropriate response) 

My personal preference would be A because the initiating gateway does not what the initiating consumer's intend is/was when it added an empty targetHomeCommunityIdList parameter to the ITI-18 request (that triggers and ITI-38 to be forwarded to remote gateways). Hence, I would suggest that an empty parameter has the same meaning as no parameter. 

Would like to hear what other think, and if we have to add this situation to the XCA profile. 

Best regard,

Andries Hamster
EVP Business Development

Phone:    +31 6 55 82 32 89
Email:      and...@founda.com
Website:  foundahealth.com

Diletta Babato

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Sep 22, 2025, 6:39:14 AM (6 days ago) Sep 22
to Andries Hamster, IHE ITI Technical Committee
Hi Andries,

I agree with you.
In my opinion, if the Responding Gateway receives an [ITI-38] with an empty value of the parameter $targetCommunityIdList, it should ignore the parameter and respond as if the parameter was not present.

Do you suggest specifying this situation in the XDS/XCA profiles?

Best Regards,
Diletta

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Diletta Babato
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Andries Hamster

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Sep 22, 2025, 8:44:24 AM (6 days ago) Sep 22
to Diletta Babato, IHE ITI Technical Committee
Hi Dilletta,

Thanks for the quick response. The question came up while we were discussing implementing this with another XDS vendor in the Netherlands. We both came to the conclusion that the profile wasn't specific on this. Hence my question. If it is not much work we may added it in the next revision of the technical framework. 

Another thing we discussed is what to do if the $targetHomeCommunityIdList included Ids that the responding gateway doesn't recognized. We made an agreement that the initiating gateway should do its best to only include homeCommunityIds that are relevant to the responding community. In case the responding community does receive a Id it cannot "resolve" it will return a partialSuccess response indicating for each homeCommunityId it does recognize a "XDSUnknownCommunity" error.

Best regards,

Andries Hamster

Diletta Babato

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Sep 24, 2025, 6:35:34 AM (4 days ago) Sep 24
to Andries Hamster, IHE ITI Technical Committee
Hi Andries,

Regarding the issue of the expected behavior of the Responding Gateway in the case of queries with empty $targetcommunityIdList parameter, I can certainly work on a CP.

Regarding the other item:
Another thing we discussed is what to do if the $targetHomeCommunityIdList included Ids that the responding gateway doesn't recognized. We made an agreement that the initiating gateway should do its best to only include homeCommunityIds that are relevant to the responding community. In case the responding community does receive a Id it cannot "resolve" it will return a partialSuccess response indicating for each homeCommunityId it does recognize a "XDSUnknownCommunity" error.

In the fourth bullet in Section 3.38.4.1.3 Expected Actions of the [ITi-38] transaction we specified that:
"If the Responding Gateway supports the Target Communities option and the $targetCommunityIdList parameter is specified, then return an XDSUnknownCommunity error code for each value which is not known by the Responding Gateway. Note that the Responding Gateway MAY continue to process the query if any values are those of communities that are known."

Therefore, according to the technical framework, the Responding Gateway returns an error for values it does not recognize, but can still process the request for those it does recognize. Do you suggest handling this scenario in a different way?

Thank you,
Diletta Babato

Andries Hamster

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Sep 25, 2025, 3:45:51 AM (3 days ago) Sep 25
to Diletta Babato, IHE ITI Technical Committee
Hi Diletta,

If you can work on a CP that would be great. I will support it :-) 

W.r.t. to the "other item" the only difference w.r.t. the current profile text is that we propose that the initiating gateway does make an effort to only forward $targetHomeCommunityIds to a remote community it "knows" that the remote community can process. It is more a courtesy of the initiating gateway to no to overwhelm a responding gateway with hcIds it cannot process but still has to do an effort for to create an error response. 

Thanks

Andries

John Moehrke

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Sep 25, 2025, 8:22:21 AM (3 days ago) Sep 25
to Andries Hamster, Diletta Babato, IHE ITI Technical Committee
That is a good note, but it brings up the question of how it can know that? Is there guidance for that, like CSD/mCSD?


John Moehrke - Architect: Standards - Interoperability, Privacy, and Security
https://MoehrkeResearch.com
https://healthcaresecprivacy.blogspot.com   

Andries Hamster

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Sep 25, 2025, 11:59:39 AM (3 days ago) Sep 25
to John Moehrke, Diletta Babato, IHE ITI Technical Committee
Hi John,

(m)CSD is a way to get such info. However, the way XCA is written an Initiating gateway must have prior knowledge of the homeCommunityIds of the responding gateways it is addressing. In other words, the XCA profiel implicitly or explicitly defines this out of scope. Hence, I would recommend not to change this. 

Best regards,

Andries Hamster 

John Moehrke

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Sep 25, 2025, 7:15:42 PM (3 days ago) Sep 25
to Andries Hamster, Diletta Babato, IHE ITI Technical Committee
Okay.


John Moehrke - Architect: Healthcare Standards - Interoperability, Privacy, and Security
https://healthcaresecprivacy.blogspot.com
https://MoehrkeResearch.com
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