Welcome to the National Screening Platform (NSP) C4 Model

This site presents the evolving architecture of the National Screening Platform (NSP) using C4 model diagrams—providing a shared, always-current view of how the platform is structured and how its parts interact.

In partnership with the EventCatalog, this platform offers a document-as-code, interactive way to explore both the current deployment and target architecture of the NSP.

Why this exists

Architecture isn’t static—and neither is this repository. We treat our architecture the same way we treat our code: it’s versioned, reviewed, and collaboratively maintained. This is a living, breathing model that reflects the decisions we’ve made, the trade-offs we’ve considered, and the direction we’re heading.

You’ll find views across all four C4 abstractions:

  • Software Systems – what NSP is and how it fits in the wider ecosystem
  • Containers – the major deployable pieces that make up the system
  • Components – the internal structure of those containers
  • Code – optional, but where appropriate, we link down to implementation detail

Each diagram is clickable and explorable, allowing you to move between levels of abstraction and see how everything fits together.

Our goal

We want this to be more than just documentation. This is a collaboration space—a place for teams to share ideas, propose designs, and collectively shape the future of the platform. If you’re contributing to NSP, you’re contributing to this architecture.

Let’s keep it up-to-date. Let’s make it better, together.

Currently deployed system context diagram

The current deployed architecture is depicted below

Current deployed System Landscape view Current deployed System Landscape view Communications Manager [Software   System]   Service   for   centralising   all communication   from screening   programmes   to the   participant NHS   Notify [Software   System]   NHS   Wide   service   for providing   communication   to the   Citizen Communicates   with the   participant using Sends   back invitation   status
Current Deployed Landscape Diagram

Target state system context diagram

This view is intended to demonstrate a longer term system landscape as more functionality and more screening programmes are adopted into the NSP

Target System Landscape view Target System Landscape view P9   Participant   users [Person]   External   user   eligible   for screening National   Breast Screening   Service [Software   System]   External   Service   used   for managing   breast   screening Communications Manager [Software   System]   Service   for   centralising   all communication   from screening   programmes   to the   participant Participant   Manager [Software   System]   Service   for   managing   a participant's   episodes   and encounters Cervical   Screening Management   System [Software   System]   External   Service   used   for managing   cervical screening Participant   Support [Software   System]   Service   for   managing inbound   help   requests   from participants Bowel   Screening System [Software   System]   External   Service   used   for managing   bowel   screening Pathway   Coordinator [Software   System]   Service   that   implements   a pathway   definition Diabetic   Eye Screening [Software   System]   External   Service   used   for managing   diabetic   eye screening Screening   Event Manager [Software   System]   Service   for   coordinating   and capturing   the   clinical investigation   processes Service   Layer [Software   System]   Service   integration   layer used   to   transition   from legacy   to   the   future platform Abdominal   aortic aneurysm [Software   System]   External   Service   used   for managing   AAA   screening Breast   Screening Select [Software   System]   NHSE   Service   used   to manage   the   cohort   of participants   for   breast screening PDS [Software   System]   NHS   Demographic   Service Service   Now [Software   System]   Ticketing   service NEIMS [Software   System]   Demographic   Change   Event NEIMS   Subscription API [Software   System]   Subscribe   and   unsubscribe NHS   Number Unauthenticated Participant   users [Person]   External   users   without   NHS Login   account Cohorting   as   a Service [Software   System]   Service   which   produces   a list   of   eligible   participants based   on   a   cohort   definition NDRS [Software   System]   Data   source   for   VHR   referral ITOC [Software   System]   Centralised   Monitoring   Log Appointment Allocator [Software   System]   Service   that   appropriately allocates   a   participant   to   a slot Appointment   Booker [Software   System]   Service   for   both   participant and   staff   to   manage appointments Staff   users [Person]   Internal   staff   users including   clinical   and administrative   staff BI   and   Data   Analysis [Software   System]   Service   for   analysing Screening   data Business   Audit [Software   System]   Service   that   provides immutable   audit   datastore used   for   analysis   and non-repudiation Secondary   users [Person]   Internal   users,   but   not concerned   with   day   to   day operations Campaign   Manager [Software   System]   Service   for   launching   and monitoring   campaigns   to improve   uptake Capacity   and   Demand Planner [Software   System]   Service   for   optimising capacity   vs   demand constraints Capacity   Manager [Software   System]   Service   to   centralise   the overall   system   capacity Cohort   Manager [Software   System] NHS   Notify [Software   System]   NHS   Wide   service   for providing   communication   to the   Citizen NHS   Login [Software   System]   NHS   Wide   service   for authenticating   the   Citizen Care   Identity   Service (CIS) [Software   System]   NHS   Wide   service   for authenticating   Staff NHS   App [Software   System]   National   Mobile   Application for   NHS Local   Trust   System [Software   System]   Local   Trust   System Gets   available   slots using Retrieves participants   usage patterns Publishes   data   to Notifies   of   business audit   events   using Publishes   data   to Manages participant appointments   using Manages appointment   using Queries   data   using Analyses   screening data   using Publishes   data   to Subscribes   to events   from Interacts   with campaigns   using Creates   campaigns using Creates unresourced   slots using Receives   demand from Manages   capacity and   demand   using Receives   capacity from Manages   Capacity using   Data   via   API Un/Subscribe   HTTP Request Sent   via   MESH Mailbox HTTP   request   by NHS   No. pds [HTTP   request] Send   monitoring logs Writes   eligibility changes, demographic   and transformation changes Published   New Eligible   Participant Event   using Communicates   with the   participant using Sends   back invitation   status Sends   back invitation   status payload Send   appointment with   pathway definition Writes   appointment invitation   statuses Notifies   of participant   ready for   screening   using Manages participant's episode (appointments, closed   episodes) using Update   episodes with   appointment statuses Notifies   of   business audit   events   using Publishes   data   to Views   screening information   using Manages participant's episode   using Protects   using Access   low   security information   using Protects   API   using Logs   on   via Notifies   of   business audit   events   using Requests   support using Manages participant   queries using Gets   slot   for participant   using Executes   clinical investigation   using Notification   of clinical   outcome using Update appointment invitation   status Manages   Pathway definitions   using Interacts   with participant screening   history using Logs   on   via Protects   API   using Notifies   of   business audit   events   using Publishes   data   to Manages   clinical investigation   using Authenticates   using Communicates   with Provides   national authentication   & authorisation services   to Emits   events   for processing   using Get   Demographic Data Sent   demographic change   event   VIA mesh Explicit subscription Get   VHR   referral Sends   breast screening   data   to Sends   cervical screening   data   to Sends   bowel screening   data   to Sends   DES screening   data   to Sends   AAA screening   data   to Authenticates   using Accesses   secure NHS   services   using Interacts   with screening   service using   HTTP   request Sent   via   Mesh Mailbox
Target System Landscape Diagram