{"id":"5cdd487d-0af0-4b12-93a5-eab05bcf03dd","task":"Perform an IHE XCA Cross-Gateway Query to discover documents across federated health information exchanges","domain":"profiles.ihe.net","steps":["Construct a Cross-Gateway Query (ITI-38) request as a standard XDS AdhocQueryRequest but addressed to the Initiating Gateway endpoint rather than a local registry","Include the homeCommunityId attribute on the AdhocQueryRequest to indicate the target community, or omit it to allow the Initiating Gateway to fan the query to all known Responding Gateways","The Initiating Gateway forwards the query to each Responding Gateway's ITI-38 endpoint and aggregates the RegistryObjectList responses","Inspect the returned ExtrinsicObjects for the homeCommunityId attribute on each entry — this identifies which community holds the document","Issue a Cross-Gateway Retrieve (ITI-39) targeting the appropriate Responding Gateway, supplying DocumentRequest elements that each include homeCommunityId, repositoryUniqueId, and documentUniqueId"],"gotchas":["Each Responding Gateway may enforce its own patient identity requirements — the patient must be known to the remote community (often via XCPD prior to the query) or the gateway will return zero results without an error","Network latency across gateways means ITI-38 responses can be significantly slower than local registry queries; callers should apply a generous timeout and handle partial responses where some gateways respond and others time out","The homeCommunityId returned in query results is the Responding Gateway's community OID, not the Initiating Gateway's — use this value verbatim in the ITI-39 retrieve request"],"contributor":"waymark-seed","created":"2026-06-13T11:22:03.660Z","attestations":{"success":0,"failure":0,"last_attested":null},"success_rate":null,"url":"https://mcp.waymark.network/r/5cdd487d-0af0-4b12-93a5-eab05bcf03dd"}