Query identification

QID identifies a previously submitted query so it can be cancelled or its status checked. It appears in QCN (cancel query) messages and carries the query tag and query name that the responding system needs to locate the original request.

QPD defines the full query parameters for a new request, while QID is a lightweight reference used only to identify an existing query by its tag and name. QID is for cancellation; QPD is for submission.

Set the query_tag to match the original query and include the query name:

from zato.hl7v2.v2_9 import QID, CWE

qid = QID()
qid.query_tag = 'Q0042'
qid.message_query_name = CWE(
    identifier='Q22',
    text='Find candidates',
    name_of_coding_system='HL70471'
)

It uses the CWE datatype with HL7 table 0471, which lists standardized query names such as Q22 (Find Candidates) and Q31 (Dispense History):

from zato.hl7v2.v2_9 import QID, CWE

qid = QID()
qid.query_tag = 'RX-0088'
qid.message_query_name = CWE(
    identifier='Q31',
    text='Dispense history',
    name_of_coding_system='HL70471'
)

Yes, query_tag is required (usage R). It is the unique identifier assigned by the querying system when the original query was submitted, and the responding system uses it to locate the query to cancel.

Zato connects to any system that speaks HL7v2 over MLLP or FHIR over REST. This includes Epic, Cerner, Meditech, Allscripts, and other EHR platforms.

Yes, Zato has built-in MLLP support for sending and receiving HL7v2 messages. MLLP channels handle the framing protocol automatically.

Zato supports HL7 v2.9, which is backward compatible with earlier versions including v2.3, v2.5, and v2.7. Standard segments and datatypes are available as typed Python classes.

Yes. Zato handles both HL7v2 and FHIR natively, so you can parse v2 messages and build FHIR resources with IG-specific extensions in the same service. Typed Python classes are available for both protocols, including extensions from US Core, UK Core, Da Vinci, and other Implementation Guides.