presentation slides - Distributed Information Systems Laboratory LSIR

mashpeemoveMobile - Wireless

Nov 24, 2013 (3 years and 6 months ago)

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“Putting Context in Context: The Role
and Design of Context Management in
a Mobility and Adaptation Enabling
Middleware


Marius Mikalsen

Research Scientist, SINTEF ICT, Norway

MCISME, Nara 09.05.06

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NASA Challenges


934 million km away


Signal takes 50 minutes to reach earth


Interesting objects may pass without being noticed


Need autonomous/adaptive space probes


NASA and similar approaches to adaptation are
characterized by tailored solutions which are high cost

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Focus of this presentation



Adaptation needed, also on earth, in mobile computing


An approach for middleware support for the development
of autonomous adaptive applications in the mobile domain
(reduce costs and time to market)


Differs from previous work in that it plays more active role
in the adaptation process



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Presentation outline


Background


Thesis


Context management in an adaptation enabling
middleware


Evaluation


Conclusion and future work




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Background


need for adaptation


Mobile applications need to adapt to changing requirements (at run
-
time)


What is an adaptive application:


Improve perceived performance by
self
-
adapting

to changing context (user and
system)


Example adaptations


User Interface



DB Proxy




Satyanarayanan’s range of adaptations strategies:



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Background


not enough system support


Much context aware system research focus on high
quality context delivery, but less focus on supporting the
adaptation process itself




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Background


some excellent context
managers



Dey’s Context Toolkit


Context widgets, context interpreters, and context aggregators


Capra’s Reflective Middleware Solution


Reflective middleware using metadata


Huebscher’s Adaptive Middleware Framework


Quality of context, context (hyper) spaces, and learning

Figure 1 Select best CP available (from Huebscher)

Figure 2 Select lest bad CP (from Huebscher)

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Background


more system support

adaptable

application

adaptation

manager

context

manager

Manages and provides context

adapts

adaptable

application

context

manager

Manages and provides context

adapts

Dey, Capra, Huebscher ++:

Adaptation middleware:

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Background


Using Adaptation Enabling Middleware



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Background


context technology matures


Redwine and Riddle’s six phases of technology
popularisation (15
-
20 years):

1.
Basic research

2.
Concept formulation

3.
Development and extension

4.
Internal enhancement and exploration

5.
External enhancement and exploration

6.
Popularization


Weiser (1991): The ubiquitous computing paradigm


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Thesis

1.
Need tool support (such as adaptation enabling
middleware) to reduce cost of building context aware
adaptive systems

2.
Utilising context information is essential to make such
adaptation possible, and need for context management
component to handle context

3.
Two main responsibilities in an adaptation enabling
middleware:


Reduce number of unnecessary adaptations.


Separate context management concerns from adaptation
reasoning



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Why do we need tool support?


Tools simplify software evolution


Simpler


separation of concerns
(
application and
adaptation behavior
)


Tools improve scalability



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Why is context information important?

monitors

influences

user
needs

needed

service quality

offered

service quality

adaptable

application

user

context

network QoS

shared

devices

battery

execution


context

adaptation

manager





position

light

noise

selects

application

variant

uses

mobile user

uses
service

context

manager

monitors

configuration

manager

uses

instructs

reconfigures

architecture model

node

component

legend
:

application

variant

link

represented as

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Context Manager’s responsibilities in the
architecture


Reduce number of unnecessary adaptations


Only occur when necessary


Notify of
significant context change


Separate context management concerns from adaptation
reasoning


... and what is our approach to achieve this?

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The context model

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Context manager components

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Context repository


Primary entry point for context clients and context sources


Separate context management concerns from adaptation
reasoning


Tasks:


Maintain context model


Register and notify clients


Enable plug
-
ins (reasoners and sensors)

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Context sensor


Context sensors sense low level or raw context information


Example network sensor:


Callback/call mechanism using the Birdstep MADAM Mobility API


Provides access to key connectivity information such as available
networks, signal strength and latency/bandwidth parameters


Supports the following network adapters (non
-
exhaustive list):


WLAN


Ethernet


GSM


GPRS


EDGE


UMTS


Bluetooth



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Context reasoner


Avoid unnecessary adaptations


Input from two sources; adaptation manager and user, on what constitutes
a
significant context change


Adaptation manager


must communicate boundary conditions (e.g. bandwidth)


Clear separation on what component reasons on what


User in the loop


Explicit


directives


Implicit


feedback


Overrides AM


Example reasoning


Artificial intelligence:


Natural fit


Challenges


context is elusive


Case based reasoning


QoC spaces (Huebscher)

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Evaluation


Two case examples to test performance


Information service to support janitor inspections and a videostreaming application


Also, two industrial pilot services with Condat and Integrasys


Results:


Defining architectural properties and utility functions need extensive tool support at
design time


The context management provides good support for accessing and identifying
context elements and works well as a manager for context information


Suggested improvements:


Need reasoning libraries


should be standardized rules in the framework as to how the user needs and preferences
influence the relative importance of other context information (user must in the loop)


should always be possible for the user to override context sensing, and explicitly state
what is the (significant) context


identified the need for more support for interoperability with third party context sensors


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Conclusion


Need tool support (such as adaptation enabling middleware) to reduce
cost of building context aware adaptive systems


Utilising context information is essential to make such adaptation
possible and one need context management component to handle
context


Two main context operations that are needed in such a middleware:


Reduce number of unnecessary adaptations.


Separate context management concerns from adaptation reasoning


Future work


Evaluate and decide on suitable reasoning mechanism for avoiding
unnecessary adaptations


Integrating context information from different sources


SOA


Ontologies