1. Reference: [1] TeamSpace paper
Building Personal Context-Aware Systems - Realizing ACAS infrastructure for personal use Wei Li Computer and Systems Sciences Department Royal Institute of Technology
Introduction
The ACAS project has developed a conceptual middleware solution to provide adaptive applications a simple access of distributed context information. This solution is built upon a number of components (named context entities), which interact with each other to form a Context Network to ensure a
desirable delivery of required information.
This poster addresses the issues toward realizing the proposed solution in the circumstance of real life, specifically about the issues of how to acquire context information from users with respect to their economical affordability and personal privacy
protection.
Real World Implementation
Bluetooth Detector: a convenient way of providing user’s location (and other) context.
Short range radio (~10m, adjustable!)
Commonly available
Less power consumption
Give rich Information (more than just MAC address)
Accessible over the net:
e.g., use Telnet :
> Telnet ServerHost 8989
> Subscribe Appeared
> Subscribe Disappeared
> Subscribe Present
> …
> Quit (or Exit)
PAN
Local Infra-structure Service
Person Centric System View
The Personal Server works as a central and persistent online representative of a user (figure 1) :
Resides on user’s home network (e.g., their home desktop PCs)
Holds a central storage of user’s context information as well as other entities like context manager, context server etc.
Acts as a remote mediator to assist user’s local communication and interaction taking consideration of their situations
<?xml version="1.0" encoding="UTF-8" ?>
<BTDevList category="present" amount="2" detector="070f " location="FuseLab Pentagon">
<BTDevice address=" c4b6" type="Computer: Handheld PC/PDA“
service="Networking ,Object Transfer , Audio" timestamp="11147V ; Fri
Apr 29 01:40:07 CET 2005" presentFrom="11147V ; Fri Apr 29 01:40:07
CEST 2005">skype:liwei</BTDevice>
<BTDevice address="000ad91452ee" type="Phone: Smart phone" service="Limited
Discovery , Object Transfer" timestamp="11147V ; Fri Apr 29 01:40:07
CEST 2005" presentFrom="11147V ; Fri Apr 29 01:40:07 CEST
</BTDevList>
Figure 1. Central Personal Server: three types of context reports arrive from difference sources: continuous context updates from user’s familiar places (e.g., home and office); irregular context reports from user’s mobile devices when their connections are intermittent; and occasional context exchange with the unfamiliar people and environment in the user’s vicinity. Each place and user may have a central context entity which aggregates the associated information
and manages the access to it.
Pseudonym Based Context Sharing
The Anonymizer Proxy Server helps to provide user privacy protection by hiding user’s real identity with pseudonyms when
communicating with untrustworthy parties (Figure ):
A pseudonym is an abstract (literally neutral) URI pointing to the user’s Anonymizer Proxy
The Anonymizer Proxy Server is hosted by a user trusted third party to provide a mapping service between user’s abstract URI and the real communication identity.
A number of pseudonym is agreed between user’s mobile system and the Anonymizer Proxy before hand
These agreed pseudonyms will be noticed (via detection) by the local parties in the proximity. And the unfamiliar parties can use this detected pseudonym to send context requests or reports to the Anonymizer Proxy Server
The Anonymizer Proxy Server will decide where and how to forward the context requests to the user’s context system based on knowledge of pseudonym mapping
The Personal Context System will also decide whether to reply the request directly or go through the Anonymizer Proxy Server again
The server produces four types of events for subscribers (context consumers): appearing, appeared, disappeared and present.
Each event consists of a list of devices, the device name in the example is set with user’s IM account
Anonymizer
Proxy
Server 1
Personal
Server 2
Personal Area
Network
People and Facilities in the Vicinity
IM Networks: an alternative realization of pseudonym based context sharing
Personal Server with IM URI:
IM Networks
SIP, MSN, Yahoo, Skype …
Local Infra-structure Service
Anonymizer Proxy Server
Name device with user’s Personal Server IM URI, like:
Bluetooth Detector
Dynamic association with Bluetooth discovery
Figure 2. A Dynamically Formed Context Network with Anonymity Support: the personal server controls the access of personal data according to the user’s permission; while the Anonymous Proxy Server helps to decrease user tractability caused by context sharing. With these two components, the user is provided better
protection for their personal data.
Demo Application: adding context (location) awareness to legacy software services (TeamSpace [1])
Personal
Area
Network
Anonymizer
Proxy
Server
Untrustworthy
Parties
(Occasionally visited
places or persons)
Abstract Pseudonym
e.g.,
To further decrease the tractability, the pseudonym name should be alterable as the situation varies, e.g., when location changes or after certain time period
Auto Mode:
Manual Mode:
Reference:
[1] TeamSpace paper
Conclusion:
By making more use of the available hardware and software technologies, we can lower the entry of context aware systems by encouraging and providing support for normal users to actively participate in constructing individual context systems which we hope will
have big impact for putting context system into real life
use.