Merge pull request #136 from open-component-model/mpas-section

Create mpas section

content/en/mpas/core_concepts.md

@@ -0,0 +1,71 @@
+---
+title: "Core Concepts"
+description: Core Concepts of Mpas.
+lead: ""
+date: 2023-09-12T10:37:58+01:00
+lastmod: 2023-09-12T10:37:58+01:00
+draft: true
+images: []
+weight: 101
+toc: true
+---
+
+This section describes the core concepts of `MPAS`. To learn more about the `MPAS` architecture,
+see [Architecture](https://github.com/open-component-model/MPAS/tree/main/docs/concepts).
+
+## Product
+
+Products are packages of software that can be deployed to targets such as Kubernetes clusters,
+virtual machines or bare-metal devices.
+
+Products are made available to the `MPAS` system as `OCM` Components via a Subscription.
+Multiple instances of a Product may be installed that refer to the same Subscription.
+
+A `ProductDeployment` is a Kubernetes Custom Resource that represents a product to 
+be deployed to a target. The `ProductDeployment` is reconciled by the `MPAS Product Controller` 
+which will generate the necessary Kubernetes resources to deploy the product to the cluster.
+
+A `ProductDeploymentGenerator` is a Kubernetes Custom Resource that represents a
+`ProductDeployment` to be deployed to a Kubernetes cluster. The `ProductDeploymentGenerator`
+is reconciled by the `MPAS Product Controller` in order to generate the `ProductDeployment` resource.
+
+A `ProductDescription` is a manifest that describes a product. It specifies the set 
+of resources that are needed to deploy the product in a form of pipeline steps.
+The `ProductDescription` is retrieved by the `MPAS Product Controller` in order to
+generate the `ProductDeployment` resource during a `ProductDeploymentGenerator` reconciliation.
+
+A `ProductDeploymentPipeline` is a Kubernetes Custom Resource that defines a resource
+that needs to be deployed as part of the `ProductDeployment`. The `ProductDeploymentPipeline` is
+reconciled by the `MPAS Product Controller` as part of the `ProductDeployment` deployment.
+
+
+## Project
+
+A `Project` is a Kubernetes Custom Resource that is used to manage the lifecycle of
+a `MPAS` project. A `Project` is reconciled by the `MPAS Project Controller` which
+will generate a project namespace and a git repository for the project containing
+the project folder structure. The controller will also generate the necessary
+`Flux kustomization` resources in the `mpas-system` namespace in order to update
+the cluster with the project resources from the git repository. All items that the 
+`MPAS Project controller` created during reconcile, are visible in the `status` subresource
+of a `Project` CR.
+
+The project git repository is designed to be used as a gitops repository for the
+project. It is where all the product custom resources are to be defined in order
+to be deployed to the cluster.
+
+## Subscription
+
+The purpose of a Subscription is to replicate `OCM` components containing a particular
+Product from a delivery registry to a registry in the `MPAS` customer's environment.
+
+A `ComponentSubscription` is a Kubernetes Custom Resource that represents a subscription
+to a component. The `ComponentSubscription` is reconciled by the `OCM Replication Controller`
+which will transfer the OCM component using the OCM library into the target registry.
+
+## Target
+
+A `Target` is a Kubernetes Custom Resource that represents a target environment where
+a `Product` is to be deployed. The `MPAS Product Controller` controller reconciles the `Target` 
+and creates any necessary prerequisite that needs to exist in the target environment, e.g.
+a namespace and service account.