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+=====================
+DCAE MOD Architecture
+=====================
+
+
+DCAE MOD is composed of a mix of components developed in ONAP and other
+components taken from the Apache Nifi project and modified for
+appropriate use.
+
+The goal of the project is to stream line the construction, management,
+and evolution of DCAE flows from role to role, from environment to
+environment, and from release to release.
+
+DCAE MOD is composed of three functional areas: onboarding, design, and
+distribution.
+
+
+Below illustrations describe the architecture of DCAE-MOD and show the
+usage flow in DCAE MOD-
+
+|image0|
+
+|image1|
+
+Onboarding API
+--------------
+
+It is a component developed to onboard
+models/components/microservices (spec files) into DCAE MOD.
+
+Genprocessor
+------------
+
+It has been developed in Java. This project is a tool to
+experiment with generating a Nifi Processor POJO from a DCAE component
+spec.
+
+Nifi Web UI
+-----------
+
+It is a component taken from the Apache Nifi Project but modified for
+use in the MOD project.
+
+Apache NiFi is a dataflow system based on the concepts of flow-based
+programming. It supports powerful and scalable directed graphs of data
+routing, transformation, and system mediation logic. NiFi has a
+web-based user interface for design, control, feedback, and monitoring
+of dataflows. It is highly configurable along several dimensions of
+quality of service, such as loss-tolerant versus guaranteed delivery,
+low latency versus high throughput, and priority-based queuing. NiFi
+provides fine-grained data provenance for all data received, forked,
+joined cloned, modified, sent, and ultimately dropped upon reaching its
+configured end-state.
+
+The NiFi UI provides mechanisms for creating automated dataflows, as
+well as visualizing, editing, monitoring, and administering those
+dataflows. The UI can be broken down into several segments, each
+responsible for different functionality of the application. This section
+provides screenshots of the application and highlights the different
+segments of the UI. Each segment is discussed in further detail later in
+the document.
+
+The users of Apache Nifi will find that it is used very differently than
+intended to serve our purpose in the DCAE-MOD project.
+
+
+Registry API
+------------
+
+This component taken from the Apache Nifi project, is a REST API that
+provides an interface to a registry with operations for saving,
+versioning, reading NiFi flows and components.
+
+Distributor API
+---------------
+
+It is a component developed using the Flask framework in Python.
+It is a HTTP API to manage distribution targets for DCAE design.
+Distribution targets are DCAE runtime environments that have been
+registered and are enabled to accept flow design changes that are to be
+orchestrated in that environment.
+
+Flow Based Programming (FBP)
+----------------------------
+
+NiFi’s fundamental design concepts closely relate to the main ideas of
+Flow Based
+Programming `[fbp] <https://nifi.apache.org/docs/nifi-docs/html/overview.html#fbp>`__.
+
+For more information on how some of the main NiFi concepts map to FBP,
+check out https://nifi.apache.org/docs/nifi-docs/html/overview.html
+
+Runtime API
+-----------
+
+It is developed in Java’s Spring Boot framework. It
+is a HTTP API to support runtime environment for DCAE-MOD. It has two
+major functionalities:
+
+1. It accepts changes on the flow-graph via fbp protocol
+
+2. It generates and distributes blueprints based on the change made on
+   the flow-graph
+
+Blueprint Generator
+-------------------
+
+This tool allows the user to create a blueprint from a component spec json file.
+This tool is used by the runtime api.
+
+Inventory API
+-------------
+
+DCAE Inventory is a web
+service that provides the following:
+
+1. Real-time data on all DCAE services and their components
+
+2. Comprehensive details on available DCAE service types
+
+DCAE Inventory is a composite API that relies on other APIs to obtain
+resources on underlying components and uses these resources to compose a
+DCAE service resource. In addition, DCAE Inventory will store data that
+is unique to the DCAE service level including:
+
+1. DCAE service metadata
+
+2. DCAE service type description and composition details
+
+3. Relationships between DCAE service and DCAE service types and their
+   respective VNF and VNF types
+
+DCAE Inventory has a REST interface to service client requests. It has a
+well-defined query interface that would filter result sets based upon
+resource attributes.
+
+Here, think of it as a back end API for the DCAE dashboard. The runtime
+posts Cloudify Blueprints to this API so they show up in the DCAE
+dashboard.
+
+DCAE Dashboard
+--------------
+
+The DCAE dashboard provides visibility into running DCAE services for
+operational purposes. It queries the DCAE Inventory for aggregate
+details on all the running DCAE services and for getting up-to-date
+status information on DCAE services and their components.
+
+End-to-End Flow
+---------------
+
+A model/component/microservice can be onboarded by a ms Developer by
+posting a spec file on the onboarding API. Alternatively, an Acumos
+model can be onboarded using the Acumos Adapter. Once successfully
+onboarded, the genprocessor converts converts them to jars and onboards
+them into Nifi i.e DCAE MOD. These artifacts are now available to use
+from the Modified Nifi Web UI i.e DCAE Designer.
+
+The registry api offers version control and retrieval for flows. The
+distributor api can be used to set distribution targets. Once a flow is
+designed and distributed, it goes to the distributor api which is
+supposed to post graph changes (in accordance with fbp) to the runtime
+api. The runtime api generates and distributes blueprints based on the
+change made on the flow-graph. These blueprints received by the DCAE
+inventory can then be viewed and deployed from the DCAE dashboard.
+
+
+
+.. |image0| image:: ../images/DCAE-Mod-Architecture.png
+
+.. |image1| image:: ../images/Onboarding-with-DCAE-MOD.png
+
+.. |image2| image:: ../images/nifi-toolbar-components.png