discowot - extensible discovery for smart things

An Extensible Discovery Service for Smart Things Mayer, S. and Guinard, D. 2011, 2nd international Workshop on the Web of Things

Simon Mayer [simon.mayer@inf.ethz.ch]

Distributed Systems Group, ETH Zurich

Environments of smart things...

Forecast: Rain

Temperature: 24˚C Please configure

forecast data source

Your fridge currently

consumes 45W

I’m located in Zurich!

Human-readable and understandable

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Environments of smart things...

Forecast: Rain

Temperature: 24˚C Please configure

forecast data source

Your fridge currently

consumes 45W

I’m located in Zurich!

What about machines?

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Temperature: 24˚C

I’m located in Zurich!

Semantic annotation of smart things...

{“data”:[{“weather-

forecast”:”Rain”}],

“name”:”MyNabaztag”}

…<div itemscope><div

itemprop=“tag=“>Illumination</div><div

itemprop=“value”>150</div></div>…

...

<div class="geo">GEO: <span

class="latitude">8.549902</span>,

<span class="longitude">-

47.378088</span></span></div>

{“consumption”:”45”,

“unit”:”Watts”,

“appliance”:”fridge”}

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Machine-readable

Semantic annotation of smart things...

{“data”:[{“weather-

forecast”:”Rain”}],

“name”:”MyNabaztag”}

…<div itemscope><div

itemprop=“tag=“>Illumination</div><div

itemprop=“value”>150</div></div>…

...

<div class="geo">GEO: <span

class="latitude">8.549902</span>,

<span class="longitude">-

47.378088</span></span></div>

Content type: application/json

Content type: text/html

Annotations: Microdata

Content type: text/html

Annotations: Microformats

{“consumption”:”45”,

“unit”:”Watts”,

“appliance”:”fridge”}

Content type:

application/json

Every smart device capable of

parsing every single format...?

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Content type:

application/json

And it gets worse...

{“data”:[{“weather-forecast”:”Rain”}],

“name”:”MyNabaztag”}

Imagine we agreed on everybody using application/json...

{“data”:{“weather-forecast”:”Rain”},

“name”:”MyNabaztag”}

{“data-item”:[{“weather-forecast”:”Rain”}],

“name”:”MyNabaztag”}

Different syntax

Different formatting

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A single, agreed upon,

standard format

Options for semantically annotating smart things

Or multiple (but few!) formats

Problem of different syntax

Probably not feasible...

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Different Syntax: OK!

A method to understand

multiple different formats

Options for semantically annotating smart things

Future formats?

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Different Syntax: OK!

An extensible method to

understand multiple

different formats

Options for semantically annotating smart things

Future formats: OK!

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Given the representation of a (Web) resource, extract interesting information about that resource regardless of the annotation format used

Goal

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Discovery based on Strategies (e.g. Microformats-Strategy)

Users can create, extend (and delete) Strategies at runtime!

Approach

DiscoWoT: Discovery Process

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DiscoWoT: Discovery Process (1)

Client knows resource’s URL: http://.../Sensor

Requests a resource description at DiscoWoT’s /analyze endpoint

GET /analyze?http://.../Sensor

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DiscoWoT: Discovery Process (2)

DiscoWoT fetches resource representation

Extraction of strategy input parameters

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DiscoWoT: Discovery Process (3)

DiscoWoT applies registered strategies to the resource representation

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DiscoWoT: Discovery Process (4)

If multiple strategies can map the representation, the resulting resource

descriptions are fused

The resulting resource description is returned

{“services”:{“unit”:”ºC”,…},…}

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DiscoWoT: Discovery Process

How to access resources behind firewalls/protected resources

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The DiscoWoT Project – Flexibility

Apply every strategy to all information accessible about submitted data

Allows to handle resources behind firewalls and protected resources!

Client should not send URL but rather send contents at that URL

Is Token a URL?

→ Try to fetch the content at its location!

→ Apply strategies to this content!

Is it text/html or application/json?

→ Apply strategies to Token itself

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GET /analyze?Token

The DiscoWoT Project – Extensibility (1)

Users inject a new strategy by POSTing to the /strategies

endpoint

Users add a mapping to a strategy by POSTing to the /strategies/{strategyID} endpoint

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POST /strategies NewStrategy.java

POST /strategies/NewStrategy mapping

The DiscoWoT Project – Extensibility (1)

Strategy?

→ Basically parsers for different formats

→ Implement the DiscoveryStrategy interface

→ e.g. MicrodataStrategy

Mapping?

→ Maps to interpret parsed values

→ Multiple mappings per strategy

→ e.g. (“my_location” → “geo”)

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POST /strategies NewStrategy.java

POST /strategies/NewStrategy mapping

The DiscoWoT Project – Extensibility (2)

Registration by sending an OpenSearch Document

Mighty Google as a fallback mechanism...

Allows to easily federate multiple DiscoWoT instances

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POST /strategies/ <OpenSearch>...</>

Conclusions

An extensible discovery service for smart things

Based on multiple discovery strategies

No problems with firewalls/access restrictions

REST from tip to toe

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Conclusions

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A great help for

decoupling service

providers and consumers

Experience

Announcement

AutoWoT project now Open Source!

Check out http://code.google.com/p/autowot

Woohooo!

Facilitating the Integration and Interaction of Real-World Services for the Web of Things (Mayer S., Guinard D., Trifa V.)

Upgrading Autowot (Barthels C., Bachelor’s Thesis)

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Thank you for your attention!

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