Given the expected high number of accessible digitally augmented devices and their communication requirements, this paper presents our work on creating a Web-based infrastructure for smart things to facilitate the integration, look-up, and interaction with such devices for human users and machines. To exploit the locality of interactions with and between smart things, the proposed infrastructure treats the location of a smart thing as its main property and is therefore structured hierarchically according to logical place identifiers. We discuss the infrastructure's look-up mechanism that leverages Web patterns to foster scalability and load balancing and features an advanced caching mechanism that greatly reduces the response time and number of exchanged messages. These properties are demonstrated in an evaluation in a simulated smart environment.

1. Searching in a Web-based
Infrastructure for Smart Things
3rd Int. Conf. on the Internet of Things, Wuxi, China, 2012
Simon Mayer, Dominique Guinard, Vlad Trifa
Distributed Systems Group, ETH Zurich, simon.mayer@inf.ethz.ch

2. The Web of Things
+ Internet Connection
+ Embedded Web server
+ Resource-Oriented Modelling (REST)
J.W. Hui and D.E. Culler. IP is dead, long live IP for wireless sensor networks, 2008
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3. Example: RESTful Sun SPOTs
 Resources and Links between them
28.5
GET
Temperature Sensor: http://host/[SpotName]/sensors/temperature
LED Switch: http://host/[SpotName]/actuators/leds/3/switch
PUT ‘on’
OK
M. Kovatsch, S. Mayer, and B. Ostermaier. Towards the Thin Server Architecture for the Internet of Things, 2012
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4. The Web of Things – Why?
 Great for open, interoperable APIs
 Greatly facilitates creation of mashups
 Web features for free
 Bookmark your devices and their functionality
 Caching for scalability, security mechanisms
 People are used to exploring the Web using a browser
 Seems to facilitate application development
D. Guinard, I. Ion, S. Mayer. In Search of an Internet of Things Service Architecture: REST or WS-*? A Developer’s Perspective, 2011
10/26/2012 IoT 2012, Wuxi, China 4

5. The Web of Things – Why?
 Great for open, interoperable APIs
 Greatly facilitates creation of mashups
 Web features for free
 Bookmark your devices and their functionality
 Caching for scalability, security mechanisms
 People are used to exploring the Web using a browser
 Seems to facilitate application development
D. Guinard, I. Ion, S. Mayer. In Search of an Internet of Things Service Architecture: REST or WS-*? A Developer’s Perspective, 2011
10/26/2012 IoT 2012, Wuxi, China 5

6. The Web of Things – Why?
 REST and SOAP on devices with limited resources
Power Consumption [mW] Completion Time [s]
 UDDI discontinued by IBM, Microsoft, SAP in 2006
 Functionality removed from Windows Server in 2010 [derekskeba.com]
 Google discontinued WS-* APIs in 2011
D. Yazar and A. Dunkels. Efficient Application Integration in IP-based Sensor Networks, 2009
10/26/2012 IoT 2012, Wuxi, China 6

7. The Web of Things – Community
 WoT Workshop Series: webofthings.org/wot
 2010 @ PerCom, Mannheim
 2011 @ Pervasive, San Francisco
 2012 @ Pervasive, Newcastle
 Community blog, LinkedIn Group, Twitter, ...
12/21/2012 UbiRobots'12 Workshop, Pittsburgh, PA 7

8. A Web-based Infrastructure for Smart Things
Overview & Requirements
 Increasing number of networked, smart devices
 More and more human-thing and thing-thing interactions
 Infrastructure to enable service discovery and
brokerage in smart spaces
 Most frequent interaction with nearby devices:
Interactions exhibit locality
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9. A Web-based Infrastructure for Smart Things
Overview & Requirements
 Exploit Locality of Interactions
 Scalability
 Self-Management
 User-friendliness
 Open, easily usable APIs
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10. To what extent can Web technologies and
patterns be applied in the design of a smart
things infrastructure?

11. A Web-based Infrastructure for Smart Things
Hierarchy of Management Nodes
 Nodes are only aware of their direct neighbors
 Nodes can be virtual or embodied (e.g., on routers or NAS)
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12. A Web-based Infrastructure for Smart Things
Device Discovery & Registration
 Device Discovery
 Router is knowledgable of connected network devices
 IP addresses exposed via OpenWRT + LuCi
 Resource Discovery
 Interpret any accessible information (e.g., location)
 Multiple interpretation strategies
(e.g., for HTML Microdata)
 Extensible at run time
S. Mayer and D. Guinard. An Extensible Discovery Service for Smart Things, 2011
10/26/2012 IoT 2012, Wuxi, China 12

13. A Web-based Infrastructure for Smart Things
Searching for Devices & Services – Query Types
 Search within the current subtree
 Exhaustive Query: Full subtree
 Best-Effort Query: Until first hit
 Cardinality Query: Until k hits
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14. A Web-based Infrastructure for Smart Things
Searching for Devices & Services – Query Types
 Search outside current subtree
 Request For Query
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15. A Web-based Infrastructure for Smart Things
Searching for Devices & Services – Query Handling
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16. A Web-based Infrastructure for Smart Things
Searching for Devices & Services – Query Handling
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17. A Web-based Infrastructure for Smart Things
Searching for Devices & Services – Query Handling
.../Floor5/queries/{queryID}
- Query representation
- # received answers
Floor5/ - Pending nodes
501/ 502/
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18. A Web-based Infrastructure for Smart Things
Searching for Devices & Services – Query Caching
.../Floor5/queries/{queryID}
- Query representation
- # received answers
Floor5/ - Pending nodes
501/ 502/
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19. Simulation Environment
 9 Nodes, 600 sensors registered to room-level nodes
 4 query types, 1000 queries each, varying concurrency
 Strong decrease of answering time with increasing
concurrency level CAQ (30) CAQ (200)
BEQ EXQ
 Query Caching works!
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20. A Web-based Infrastructure for Smart Things
Searching for Devices & Services – Automatic Load Balancing
.../Floor5/queries/{queryID}
- Query representation
- # received answers
Floor5/ - Pending nodes
501/ BEQ 502/
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21. Simulation Environment
 9 Nodes, 600 sensors registered to room-level nodes
 BEQs to /MainBuilding
 Baseline: > 90% of answers from /Floor5
 Flooding of /Floor5: > 96% of answers from /Floor6
 Load Balancing works!
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22. Conclusions
 Web patterns to create a smart things infrastructure
 “All you need is HTTP”?!
 “Resource-oriented Querying” scales, reduces
response time, and enables automatic load balancing
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23. Future Work
 Integrate with relative indoor localization system
 Extend resources with semantic descriptions for M2M
service provisioning
 Enhance current keyword-based searching
mechanism
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24. Acknowledgements
 Matthias Kovatsch, Dominique Guinard, Vlad Trifa
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