Draft: Add documentation

Draft of the documentation for EDDIE.

DOCS.md

+# EDDIE project
+The eddie repository is home of a middleware in the Oniro Project to enable distributed intelligence on Oniro devices.
+
+The objective of the EDDIE project is to design a middleware running on top of the operating system of the various Oniro devices, 
+capable of giving to the applications and services a global view on a unified pool of virtual resources 
+that can be exploited for an efficient execution of any application or service required by the user.
+
+## Build instructions
+
+### Prerequisites
+The following part of the document details how to install
+and configure all packages and libraries required to have
+a working copy of EDDIE.
+
+- libcoap
+
+libcoap is a C implementation of the application-level protocol CoAP.  
+The version of libcoap currently used by EDDIE is `version 4.3.0`.  
+
+
+libcoap itself requires some package to correctly complete its installation procedure:
+they can be installed with the following commands:
+
+```console
+$ (sudo) apt-get install autoconf -y
+$ (sudo) apt-get install libtool -y
+```
+
+Then launch these commands to install libcoap in your machine:
+
+```console
+$ git clone https://github.com/obgm/libcoap.git
+$ git checkout release-4.3.0
+$ cd libcoap
+$ ./configure --disable-documentation --disable-dtls
+$ make
+$ (sudo) make install
+$ (sudo) ldconfig
+```
+  For further details on libcoap have a look at the [github repository](https://github.com/obgm/libcoap)
+  and at the [official libcoap documentation page](https://libcoap.net/).
+
+- Glib  
+
+Installation instructions for Glib and its requirements can be found at the 
+[Glib installation page](https://github.com/GNOME/glib/blob/main/INSTALL.md?plain=1).
+
+### Build
+- If you want to run EDDIE on your local machine build the CMake project:
+
+```console
+$ mkdir build && cd build
+$ cmake ..
+$ make
+```
+then you can run one of the following binaries:
+`resource-directory`,
+`eddie-endpoint`,
+`eddie-virt-server` or
+`eddie-virt-client`
+
+- If you want to build the Oniro Blueprint for the EDDIE project, and run on an Oniro supported target: follow the instructions in the [EDDIE blueprint git repository](https://booting.oniroproject.org/distro/blueprints/eddie/meta-oniro-blueprints-eddie).
+
+## EDDIE structure
+The structure of the EDDIE project is horizontally divided into layers and 
+this division is reflected structure of the EDDIE repository.  
+
+While the communication and the virtualization layer are detailed below and already present in the EDDIE repository,
+an intelligent layer is planned, to enable reasoning and smart resource distribution across the EDDIE network. 
+Currently, there is only a mocked version of this layer.  
+
+Lastly an application management layer is also planned, providing advanced functionalities for process management 
+in both local and remote EDDIE nodes.  
+
+### Layers
+In the following paragraphs there is a more detailed description of the layers of EDDIE.
+
+- **Communication Layer**
+
+
+  The bottommost component of EDDIE is the communication layer: it is responsible for all the networking bits of EDDIE, 
+  from the creation and setup of the connection to the message dispatching to other nodes.  
+
+  Every device that runs EDDIE has a server component, application logic that describes what capabilities (resources) that device has and answers to requests from other nodes.  
+  Alongside the server element, a EDDIE device is equipped with a client component, allowing the device to comunicate actively in the network, performing requests to other devices.  
+
+  Additionally, one node in the EDDIE network is elected as Resource Directory (RD): a new EDDIE node that wants to connect to the network should post its description in the RD, while from the RD he can retrive the descriptions of other nodes.  
+
+  The communication layer exposes a list of APIs to the higher layers of EDDIE, allowing complex actions and queries to be executed in the EDDIE network.  
+  <!-- The APIs exposed are:
+  - `API 1`
+  - `API 2`
+  - `API 3`
+  - `API 4`   -->
+
+
+- **Virtualization layer**  
+
+
+  The Virtualization layer is responsible for the interaction between the EDDIE network (through the communication layer) and the single EDDIE-enabled application running on the device.
+
+  This layer is composed of two elements that are communicating through the IPC mechanism of d-bus: the receiver component exposes over d-bus its interface and its functions, while the sender component is able to send requests over d-bus
+
+  This layer contains a receiver component that exposes its API on d-bus, allowing multiple applications to interact with EDDIE at the same time.
+  The API is composed of a single function `PerformAction` that models the action that the application wants to execute on the network, like changing or getting the status of a resource.  
+
+  A sender component is also present in the virtualization directory with the role of transmitting the requets generated by EDDIE-enabled application to the EDDIE component of the device.    
+  
+   
+## Common usage patterns (Internals)
+Examples on how to use the internal functions of EDDIE can be found in `/linux/examples`.  

[Francesco Pham]

...this division reflects the structure...

[Francesco Pham]

-  Additionally, one node in the EDDIE network is elected as Resource Directory (RD): a new EDDIE node that wants to connect to the network should post its description in the RD, while from the RD he can retrive the descriptions of other nodes.  
+  Additionally, one node in the EDDIE network is elected as Resource Directory (RD): a new EDDIE node that wants to connect to the network should post its resources description in the RD, while from the RD it can retreive the descriptions of other nodes.  

[Francesco Pham]

maybe we will put a reference to the doxygen api documentation

[Francesco Pham]

This paragraph repeats what is being said in the following paragraphs