docs/developer/system/architecture.md
# :european_castle: System Overview
## User Requirements
The DTaaS software platform users expect a single platform
to support the complete DT lifecycle. To be more precise,
the platform users expect the following features:
1. **Author** – create different assets of the DT on the
platform itself. This step requires use of some software
frameworks and tools whose sole purpose is to author
DT assets.
1. **Consolidate** – consolidate the list of available DT assets
and authoring tools so that user can navigate the library
of reusable assets. This functionality requires support
for discovery of available assets.
1. **Configure** – support selection and configuration of
DTs. This functionality also requires support for validation
of a given configuration.
1. **Execute** – provision computing infrastructure on demand to
support execution of a DT.
1. **Explore** – interact with a DT and explore the results
stored both inside and outside the platform. Exploration
may lead to analytical insights.
1. **Save** – save the state of a DT that’s already in the
execution phase. This functionality is required for on
demand saving and re-spawning of DTs.
1. **Services** – integrate DTs with on-platform or external
services with which users can interact with.
1. **Share** – share a DT with other users of their organisation.
## System Architecture
The figure shows the system architecture of the the DTaaS software platform.
### System Components
The users interact with the software platform using a webapp.
The service router is a single point of entry for direct access to the platform
services. The service router is responsible for controlling user access to
the microservice components. The service mesh
enables discovery of microservices, load balancing and authorization
functionalities.
In addition, there are microservices for catering to managing
DT reusable assets, platform services, DT lifecycle manager,
DT execution manager, accouting and security.
The microservices are complementary and composable; they fulfil
core requirements of the system.
The microservices responsible for satisfying the user requirements are:
1. **The security microservice** implements
role-based access control (RBAC) in the platform.
1. **The accounting microservice** is responsible for keeping track of the
live status of platform, DT asset and infrastructure usage. Any licensing,
usage restrictions need to be enforced by the accounting
microservice. Accounting is a pre-requisite to commercialisation of
the platform.
Due to significant use of external
infrastructure and resources via the platform, the accounting
microservice needs to interface with accounting systems of
the external services.
1. **User Workspaces** are virtual environments in which users can perform
lifecycle operations on DTs. These virtual environments are either docker
containers or virtual machines which provide desktop interface to users.
1. **Reusable Assets** are assets / parts from which DTs are created.
Further explation is available on
the [assets page](../../user/servers/lib/assets.md)
1. **Services** are dedicated services available to all the DTs and
users of the DTaaS platform. Services build upon DTs and
provide user interfaces to users.
1. **DT Execution Manager** provides virtual and isolated execution
environments for DTs. The execution manager is also responsible
for dynamic resource provisioning of cloud resources.
1. **DT Lifecycle Manager** manages the lifecycle operations on all DTs.
It also directs _DT Execution Manager_ to perform execute, save and
terminate operations on DTs.
If you are interested, please take a look at
the [C4 architectural diagram](C4-L2_diagram.png).
A mapping of the architectural components to related pages in
the documentation is available in the table.
| System Component | Doc Page(s) |
| :---------------- | :--------------------------------------------------------------------------------------------------------------------------------------- |
| Service Router | [Traefik Gateway](https://github.com/INTO-CPS-Association/DTaaS/tree/feature/distributed-demo/servers/config/gateway#the-gateway-server) |
| Web Application | [React Webapplication](../client/client.md) |
| Reusable Assets | [Library Microservice](../servers/lib/lib-ms.md) |
| Services | [Third-party Services](./../../admin/services.md) (MQTT, InfluxDB, RabbitMQ, Grafana and MongoDB) |
| DT Lifecycle | Not available yet |
| Security | [Gitlab OAuth](../../admin/client/auth.md) |
| Accounting | Not available yet |
| Execution Manager | Not available yet |
## References
Font sources: [fileformat](https://www.fileformat.info)