1. 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

2. Environments of smart things...
Temperature: 24˚C Please configure
forecast data source
Human-readable and understandable
Your fridge currently
consumes 45W
Forecast: Rain
I’m located in Zurich!
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3. Environments of smart things...
Temperature: 24˚C Please configure
forecast data source
What about machines?
Your fridge currently
consumes 45W
Forecast: Rain
I’m located in Zurich!
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4. Semantic annotation of smart things...
…<div itemscope><div ...
Temperature: 24˚C
itemprop=“tag=“>Illumination</div><div
itemprop=“value”>150</div></div>…
Machine-readable
{“consumption”:”45”,
{“data”:[{“weather- “unit”:”Watts”,
forecast”:”Rain”}], “appliance”:”fridge”}
“name”:”MyNabaztag”}
<div class="geo">GEO: <span
class="latitude">8.549902</span>,
<span class="longitude">-
I’m located in Zurich!
47.378088</span></span></div>
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5. Semantic annotation of smart things...
…<div itemscope><div ...
Content type: text/html
itemprop=“tag=“>Illumination</div><div
Annotations: Microdata
itemprop=“value”>150</div></div>…
Every smart device capable of
parsing every single format...?
{“consumption”:”45”,
{“data”:[{“weather- Content type:
“unit”:”Watts”,
forecast”:”Rain”}],
Content type: application/json application/json
“appliance”:”fridge”}
“name”:”MyNabaztag”}
<div class="geo">GEO: <span
class="latitude">8.549902</span>,
Content type: text/html
<span class="longitude">-
Annotations: Microformats
47.378088</span></span></div>
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6. And it gets worse...
Imagine we agreed on everybody using application/json...
{“data”:[{“weather-forecast”:”Rain”}],
“name”:”MyNabaztag”}
{“data-item”:[{“weather-forecast”:”Rain”}],
“name”:”MyNabaztag”}
Different syntax
{“data”:{“weather-forecast”:”Rain”},
Content type: “name”:”MyNabaztag”}
application/json Different formatting
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7. Options for semantically annotating smart things
Or multiple (but few!) formats
A single, agreed upon,
standard format
Problem of different syntax
Probably not feasible...
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8. Options for semantically annotating smart things
A method to understand
multiple different formats
Different Syntax: OK!
Future formats?
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9. Options for semantically annotating smart things
An extensible method to
understand multiple
different formats
Different Syntax: OK!
Future formats: OK!
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10. Goal
Given the representation of a (Web) resource,
extract interesting information about that resource
regardless of the annotation format used
Approach
 Discovery based on Strategies (e.g. Microformats-Strategy)
 Users can create, extend (and delete) Strategies at runtime!
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11. DiscoWoT: Discovery Process
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12. DiscoWoT: Discovery Process (1)
GET /analyze?http://.../Sensor
 Client knows resource’s URL: http://.../Sensor
 Requests a resource description at DiscoWoT’s /analyze endpoint
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13. DiscoWoT: Discovery Process (2)
 DiscoWoT fetches resource representation
 Extraction of strategy input parameters
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14. DiscoWoT: Discovery Process (3)
 DiscoWoT applies registered strategies to the resource representation
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15. DiscoWoT: Discovery Process (4)
{“services”:{“unit”:”ºC”,…},…}
 If multiple strategies can map the representation, the resulting resource
descriptions are fused
 The resulting resource description is returned
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16. DiscoWoT: Discovery Process
 How to access resources behind firewalls/protected resources
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17. The DiscoWoT Project – Flexibility
GET /analyze?Token
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
 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
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18. The DiscoWoT Project – Extensibility (1)
POST /strategies NewStrategy.java
POST /strategies/NewStrategy mapping
 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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19. The DiscoWoT Project – Extensibility (1)
POST /strategies NewStrategy.java
POST /strategies/NewStrategy mapping
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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20. The DiscoWoT Project – Extensibility (2)
POST /strategies/ <OpenSearch>...</>
 Registration by sending an OpenSearch Document
 Mighty Google as a fallback mechanism...
 Allows to easily federate multiple DiscoWoT instances
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21. 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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22. Conclusions
Experience
A great help for
decoupling service
providers and consumers
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23. Announcement Woohooo!
 AutoWoT project now Open Source!
 Check out http://code.google.com/p/autowot
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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24. Thank you for your attention!
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