---
title: wot-rust dev notes
tags: wp2, blog, published
---

# Introducing wot-rust

As part of the contribution from [Luminem](https://github.com/luminem), we are developing a full implementation of the [Web of Things](https://www.w3.org/WoT/wg/).

We are developing it using [rust](https://rust-lang.org) giving a real-life field-test for the developer guidelines and tools we are co-developing with the [Software Engineering group @ PoliTO](https://github.com/SoftengPoliTo/).

## Web of Things

Web of Things is a set of W3C specification that aim to address a number of shortcomings around **Connected Devices** pretty much in the same way the **Web** specifications solved the problems regarding browser interoperability.

The key concept is that a connected device (in WoT jargon **Thing**) should be fully controllable by having just the knowledge of its **Description**.

A **Thing Description** uses [JSON-LD](https://www.w3.org/TR/json-ld11/) to provide the full information on how to interact with a generic **Thing**, exposing its capability through the concept of **Affordances**.

There are three kind of affordances:
- `Property`, a directly exposed state, that can be directly read or wrote.
- `Action`, a mean to give an arbitrary complex task to the Thing and then get the result of its execution.
- `Event`, an informative message that a Thing may emit at will.

Every Affordance offers information on how to reach the mapped interaction point and how to format data via **Forms** and **DataSchemas**.

It looks like this:

{
    "@context": "https://www.w3.org/2022/wot/td/v1.1",
    "id": "urn:dev:ops:32473-WoTLamp-1234",
    "title": "MyLampThing",
    "securityDefinitions": {
        "basic_sc": {"scheme": "basic", "in": "header"}
    },
    "security": "basic_sc",
    "properties": {
        "status": {
            "type": "string",
            "forms": [{"href": "https://mylamp.example.com/status"}]
        }
    },
    "actions": {
        "toggle": {
            "forms": [{"href": "https://mylamp.example.com/toggle"}]
        }
    },
    "events":{
        "overheating":{
            "data": {"type": "string"},
            "forms": [{
                "href": "https://mylamp.example.com/oh",
                "subprotocol": "longpoll"
            }]
        }
    }
}

And being a **JSON-LD**, its [@context](https://www.w3.org/TR/json-ld11/#the-context) can be used to add additional information and extend its expressivity, e.g supporting additional [protocols](https://w3c.github.io/wot-binding-templates/#protocol-intro) or providing more details.

In [SIFIS-Home](https://sifis-home.eu) we try to make so that every [potential hazard](https://www.sifis-home.eu/ontology) related to the use of a **Connected Device** is evident to the user and the to the system controlling it.

The **Thing Description** can easily use our [hazard ontology](https://www.sifis-home.eu/ontology) by adding it to the `@context`, and any program using it (**Consumer** in WoT jargon) can use or ignore the additional information as it see fit. A SIFIS-Home WoT Device can be still used by any WoT implementation.

## wot-rust

We split our implementation in multiple crates, to keep the different concers [separated](https://en.wikipedia.org/wiki/Separation_of_concerns):

- [wot-td](https://crates.io/crates/wot-td) Only focuses on building, serialising and deserialising the **Thing Descriptions**
- [wot-serve](https://crates.io/crates/wot-serve) Simplifies the creation of the application server that exposes the **Thing** affordances to the world. As the first release we only support HTTP via [axum](https://github.com/tokio-rs/axum).
- [wot-discovery](https://crates.io/crates/wot-discovery) Let you find and keep a Directory of Things available in your network.
- [wot-consume](https://crates.io/crates/wot-consume) Simplifies using a **Thing** by abstracting away as many details as possible. It is the moral dual of **wot-serve** and it is a wrapper around [reqwest](https://crates.io/crates/reqwest).

During the next weeks we'll publish more blogpost about our implementation journey, our interaction with the larger WoT-wg community and how this technology is being used in SIFIS-Home.

## Author

[Luca Barbato](https://github.com/lu-zero) is a long-time Open Source contributor, member of VideoLan, Gentoo, X.org and a few other organizations. He participates in SIFIS-Home with his company, [Luminem SRL](https://luminem.it).