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CCM-12274: Updated sequence diagram following recent decisions #30

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RossBugginsNHS merged 1 commit into from
Oct 10, 2025
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CCM-12274: Updated sequence diagram following recent decisions #30

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38 changes: 17 additions & 21 deletions docs/diagrams/digital-letters-sequence.md
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Original file line number Diff line number Diff line change
Expand Up @@ -13,35 +13,32 @@ author: Tom D'Roza

## Questions

- 1. Should we validate the CommunicationRequest schema?
- 2. (&14) This would result in two separate PDS hits
- 3. Should Notify virus check the payload given that files >10MB don't go to PDM/NDR
- 7. When does Notify delete its local copy?
- 11. Duration and interval of polling
- 21. Can NHSApp read callback go to notify-letters when the message request originated from notify-core?
1. When does Notify delete its local copy?
2. Duration and interval of polling
3. Can NHSApp read callback go to notify-letters when the message request originated from notify-core?

## Decisions

1. Out of scope for MVP: Virus checking of PDF received from Trust
2. Don't check `CommunicationRequest` filesize. Attempt to upload all `CommunicationRequest`s to PDM. Those exceeding APIM size limit will fail.
3. No PDS check by Digital Letters component of Date-of-Death, S-flag, RFR codes. Rely on Trusts having performed these checks.

```mermaid

sequenceDiagram
actor trust as Trust
participant notify-letters as Notify: Digital Letters
participant pdm as PDM
participant ndr as NDR
participant notify-core as Notify: Core
participant notify-supplier as Notify: Supplier API
participant pds as PDS
participant nhsapp as NHSApp
participant pdm as PDM
participant ndr as NDR

autonumber

trust -> notify-letters: MESH (CommunicationRequest)
notify-letters -> notify-letters: validate(schema, pdf)?
notify-letters -> notify-letters: virus-check?
opt Optionally check PDS
notify-letters ->> pds: GetPatient (NHSNumber)
pds -->> notify-letters: 200 OK (Patient)
notify-letters -> notify-letters: validate(death,sflag, rfr)
end
notify-letters ->> notify-letters: Store CommunicationRequest (S3)
notify-letters ->> notify-letters: Create SendLetter TTL
notify-letters ->> pdm: POST /CommunicationRequest
activate pdm
pdm -) ndr: SFTP
Expand All @@ -51,7 +48,7 @@ sequenceDiagram
notify-letters ->> pdm: GET /CommunicationRequest/<id>
pdm ->> notify-letters: 200 OK (CommunicationRequest)
end
rect rgb(204, 223, 241)
rect rgba(5, 26, 46, 1)
note over notify-letters,nhsapp: Existing Notify behaviour
notify-letters ->> notify-core: post /v1/messages (NHSApp)
activate notify-core
Expand All @@ -66,12 +63,11 @@ sequenceDiagram
deactivate notify-core
end

notify-letters ->> notify-letters: Create SendLetter TTL
alt Letter is read in NHS App
nhsapp ->> notify-letters: Callback(status: read)
notify-letters ->> notify-letters: Delete TTL
else Letter is not read after fallback wait time
notify-letters ->> notify-letters: Delete SendLetterTTL
else Read receipt not received within print expiry time
notify-letters ->> notify-letters: SendLetter TTL expires
notify-letters ->> notify-supplier: SendLetter(PDF)
notify-letters ->> notify-supplier: SendLetter Event
end
```
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