Update of feature list (#216)

* Straightforward updates to feature list.

* Marked fixed message sizes as explicit decision.

* Update _docs/overview/features/index.md

Co-authored-by: Pablo Garrido <pablogs9@gmail.com>

Co-authored-by: Pablo Garrido <pablogs9@gmail.com>

Author: ralph-lange

_docs/overview/features/index.md

@@ -12,25 +12,25 @@ Feature | Status
 Discovery, transport and serialization over DDS | Use of resource-optimized middleware standard [DDS for Extremely Resource Constrained Environments (DDS-XRCE)](https://www.omg.org/spec/DDS-XRCE/), implemented by [Micro XRCE-DDS](https://github.com/eProsima/Micro-XRCE-DDS) and compatible with standard DDS via an XRCE Agent on connected stronger microprocessor.
 Support for multiple DDS implementations, chosen at runtime | Support is possible in principle, but at compile-time only. So far there is only one DDS-XRCE implementation available, namely [Micro DDS-XRCE](https://github.com/eProsima/Micro-XRCE-DDS).
 Common core client library that is wrapped by language-specific libraries | micro-ROS uses the core library [rcl](https://github.com/ros2/rcl/) from ROS 2 mainly as-is. The [rclc](https://github.com/micro-ROS/rclc) package provides convenience functions and an executor for use of rcl+rclc as an API for the C programming language. The standard rclcpp, which makes extensive use of dynamic data structures, may be used on MCUs with sufficient RAM.
-Publish/subscribe over topics | Concept available as known from ROS 2. Convenience functions for creation of publishers and subscriptions in C provided in [rclc](https://github.com/micro-ROS/rclc). *However, currently, micro-ROS supports fixed-size message types only.*
-Clients and services | Concept available as known from ROS 2. *Convenience functions not yet provided and current implementation supports fixed-size message types only.*
-ROS 1 - ROS 2 communication bridge | Not applicable, but the standard ROS 1 - ROS 2 bridge can be used via micro-ROS-Agent on a stronger microprocessor to communicate with micro-ROS nodes.
-Quality of service settings for handling non-ideal networks | Reliable and best-effort semantics available. It can be set at compile-time. *Still under development.*
+Publish/subscribe over topics | Concept available as known from ROS 2. Convenience functions for creation of publishers and subscriptions in C provided in [rclc](https://github.com/micro-ROS/rclc). Note that micro-ROS supports fixed-size message types only to avoid dynamic memory allocations.*
+Clients and services | Concept available as known from ROS 2. Note that micro-ROS supports fixed-size message types only to avoid dynamic memory allocations. *Convenience functions for clients and services as well as support by the rclc Executor are under development.*
+ROS 1 -- ROS 2 communication bridge | Not applicable, but the standard ROS 1 -- ROS 2 bridge can be used via micro-ROS-Agent on a stronger microprocessor to communicate with micro-ROS nodes.
+Quality of service settings for handling non-ideal networks | Two QoS semantics, reliable and best-effort semantics, are provided. It can be set at compile-time.
 Inter- and intra-process communication using the same API | No shared-memory interprocess communication on the MCU available, but all communication is performed via the micro-ROS-Agent running on a connected microprocessor. *Efficient shared-memory communication on the MCU is considered as an important feature for future releases.*
 Composition of node components at compile-, link- or dlopen-time | Composition at compile-time only. Composition at runtime would depend highly on the RTOS.
 Support for nodes with managed lifecycles | The [rclc_lifecycle](https://github.com/micro-ROS/rclc/blob/master/rclc_lifecycle/) package provides an `rclc_lifecycle_node` type which bundles an rcl node with the lifecycle state machine as well as corresponding convenience functions.
 DDS-Security support | DDS security is supported at micro-ROS-Agent. *Security mechanisms in Micro XRCE-DDS are planned for future releases.*
 Command-line introspection tools using an extensible framework | From a remote microprocessor all standard ROS 2 tools can be used to introspect the micro-ROS nodes on an MCU. micro-ROS nodes appear as ROS 2 nodes (by the micro-ROS-Agent). Note, however, that the node graph API is currently *not* available on the MCU.
 Launch system for coordinating multiple nodes | No launch system for the micro-ROS nodes on an MCU available. Such a system would depend highly on the RTOS. The system-modes concept developed with micro-ROS allows runtime configuration/orchestration of ROS 2 and micro-ROS nodes together.
 Namespace support for nodes and topics | Available just as in ROS 2.
-Static remapping of ROS names | *Should be available if passed as argument via standard rcl API - to be checked.*
+Static remapping of ROS names | *Should be available if passed as argument via standard rcl API -- to be checked.*
 Demos of an all-ROS 2 mobile robot | Demos of several ROS 2 + micro-ROS robots available. See [https://micro-ros.github.io/docs/tutorials/demos/](https://micro-ros.github.io/docs/tutorials/demos/).
 Support for real-time code | The [rclc Executor](https://github.com/micro-ROS/rclc/tree/master/rclc) provides mechanisms for implementing real-time-critical applications with micro-ROS.
 Support for "bare-metal" microcontrollers | Bringing ROS 2 onto MCUs is all that micro-ROS is about. A crucial difference to this requirement from the early design phase of ROS 2 is that micro-ROS assumes an RTOS (e.g., [FreeRTOS](https://www.freertos.org/), [Zephyr](https://www.zephyrproject.org/), or [NuttX](http://nuttx.apache.org/)).
 IDL | Same message IDL as with ROS 2, but use of resource-optimized CDR serialization implementation named [Micro-CDR](https://github.com/eProsima/Micro-CDR).
-Build system | Build systems of NuttX and FreeRTOS integrated with colcon. *Integration of Zephyr's build system with colcon is in progress.* The build system is likely the most fragile part of micro-ROS w.r.t. the long-term maintenance, due to the many dependencies.
+Build system | Build systems of NuttX, FreeRTOS, and Zephyr are integrated with colcon. Furthermore, micro-ROS is provided as a component for ESP-IDF also as a standalone Zephyr module. The build system is likely the most fragile part of micro-ROS w.r.t. the long-term maintenance, due to the many dependencies.
 Continuous Integration | Currently, the CI for micro-ROS is distributed to GitHub and Gitlab. *Until the end of 2020, all CI should be moved migrated completely to the new CI actions of GitHub.* Please note that those packages that are released for standard ROS 2 are also built and tested on [build.ros2.org](http://build.ros2.org/).
 Documentation | High-level documentation at [micro-ros.github.io](https://micro-ros.github.io/). For detailed information please consult the README.md files in the relevant micro-ROS repositories at [github.com/micro-ROS/](https://github.com/micro-ROS/).
 Logging | *Could be available as part of the standard logging mechanism in principle but not supported by Micro-XRCE-DDS due to dynamic message size. To be checked ...*
-Time-related: Support of rate and sleep with system clock | rcl timers use POSIX API. Tested successfully on NuttX, but the resolution is very low. A higher resolution could be achieved with hardware timers - which highly depends on the MCU and possibly the RTOS. *This feature requires further investigation.*
+Time-related: Support of rate and sleep with system clock | rcl timers use POSIX API. Tested successfully on NuttX, but the resolution is very low. A higher resolution could be achieved with hardware timers -- which highly depends on the MCU and possibly the RTOS. *This feature requires further investigation.*
 Time-related: Support for simulation time | *Might be supported out of the box, but needs to be checked.* We consider HIL setups with simulation time to be corner cases.