Declarative Devices in Thingpedia

Thingpedia provides a way to connect to devices that use common protocols with no additional JavaScript code. Currently, we support RSS feeds (in Atom or RSS 1.0 format), and Generic REST APIs that return JSON. Note that if a device needs OAuth or other customized computation on the return results, a Javascript code package is required.

RSS Feed

We provide a simple interface to connect RSS feed services with Almond. You can find an example in Tutorial 1.

Five parameters are supported:

  • title
  • link (the link to the original page, in type URL)
  • updated (the updated time of the feed, in type Date)
  • description
  • picture_url

Note that some RSS feed may only contains title and link. Check the RSS feed format carefully and DO NOT use an argument if it is not in the feed of your service.

Generic REST

If a device uses generic RESTful APIs and returns the data in JSON format, loader from @org.thingpedia.generic_rest.v1 will help you connect the device easily.

In the following, let's go through a simple example: Quotes. Quotes uses the API provided by forismatic.com, which requires no authentication or developer key. It returns a random quote in JSON format as follows:

{
    "quoteText": "Always seek out the seed of triumph in every adversity.",
    "quoteAuthor": "Og Mandino",
    "senderName":"",
    "senderLink":"",
    "quoteLink":"http://forismatic.com/en/23e53ff443/"
}

To create a device for this service in Thingpedia, we define the device class as follows:

class @com.forismatic.quotes {
  // tell the system the device uses generic rest
  import loader from @org.thingpedia.generic_rest.v1();

  // the function to return a random quote
  query get(out text: String #[json_key="quoteText"],
            out author: String #[json_key="quoteAuthor"])
  #_[confirmation="a quote"]
  #_[formatted=[{type="text",text="${text} By ${author}."}]]
  #[doc="get a quote"]
  #[url="http://api.forismatic.com/api/1.0/?method=getQuote&format=json&lang=en"];
}

The device class contains one query function called "get", which returns a random quote. We first need to tell the system where we get the data from. We use the annotation url to specify the URL of the API end point for this function, as shown in the last line.

Then we need to choose the parameters we care about from the JSON output. In this example, we want quoteText and quoteAuthor. Thus, we add two output parameters, text and author, both in type String. Then for each of them, we use annotation json_key to specify the corresponding filed name from the JSON. Thus we have

out text: String #[json_key="quoteText"]

and

out author: String #[json_key="quoteAuthor"]

If the parameter name is the same with the corresponding field name in JSON, the json_key annotation can be omitted.

Then, put the code in manifest.tt, add some example commands in dataset.tt, and submit. No Javascript needed!