1/14/2016 11:59 pm1/14/2016 11:59 pm1/14/2016 11:59 pm research overview koen victor, 12/2007

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Research Research overviewoverview

Koen Victor, Koen Victor, 12/200712/2007

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Topics Topics • Introduction

Goal of this work Two examples Problem description

• Approach Addressing scheme

• Design• Notation• Coupling with the Overlay Network• Mapping to the Overlay Network

Overlay network• Design & Structure• Functionality

Architecture• Related Work

Problem Problem • In an unstructured mobile network,

addressing data / devices / services is hard (objects): Name of the object Exact address in the network -> Implies knowledge the user may not have

• Much information that is available to the user cannot be used to address objects Contextual information Relational information

• When an object connects to a network, it needs to integrate in the existing infrastructure

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Example: event in Yolande’s Example: event in Yolande’s agendaagenda

• Traditional way: synchronize via central server

Central Calender System

• Need exact address of CSS: Internet access

•Could both be online and available, but CSS offline

•Not known whether this is the best way to schedule a meeting

•Both need to synchronize to have the latest CSS information

Example: event in Yolande’s Example: event in Yolande’s agendaagenda

• Proposed way: context supported addressing

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• Where is Yolande?

•Does she have an agenda? Where is it?

•(How) Does she want to be notified now?

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Example: print on nearest Example: print on nearest printerprinter

• Traditional way: name printer using location

p2a-duplexp2a-slide

p1a

p4a

p3a

•Know the naming scheme

•Default printer is not always the closest

•Unavailable printer

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p2a-duplexp2a-slide

p1a

p4a

p3a

“Print this document on the printer that is closest to me”



• Several questions: Where is the person printing the document? What are the nearest printers? What of these printers are suitable? What of these are available?

• Alternative addresses:“Print this document on the printer that is closest to my desk”

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Goal of this workGoal of this work• Address objects using

Specification of object features Specification of context of the object

• In an unstructured mobile network As seen by the user Possibly with gateways to Internet or other

networks User doensn’t deal with network related issues

• Facilitating: Knowing whether the object is addressable Knowing whether the object is available Communication via the real network address,

and higher level protocols• Meaning of address depends on its context

AdvantagesAdvantages• Meaning of address depends on context

<-> Fixed address may become invalid when context changes e.g. printer closest to me

• No knowledge of network, infrastructure, technical details, availability… necessary These parameters are filled in by contextual

information e.g. no obligatory calendar synchronization

• Depends on all interested parties: e.g. by both issuer and addressee Me: ‘printers nearest to me’ Sysadmin: ‘for which ‘me’ has access’

• One simple address specification may deal with a lot of contextual information and policies

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Building blocksBuilding blocks• Address notation

Flexible enough to specify a variety of addresses Stringent enough to allow address checking and

avoid unnecessary ambiguity • Reasoning & Selection

What does the address mean? What is the relevant context information / policies

in the network?• Searching

Where to find the relevant context information? Where to find inference schemes to do reasoning?

• Structuring & Storing How to allow new objects to the network?

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Addressing SchemeAddressing Scheme

Design

Overlay network

1414


Design

“Place a meeting in the agenda of Yolande”•Address is as simple as possible•Ambiguity: there may be several Yolandes

contextual parameters from the initiating application: Yolande of the research group

Complete the address with

•Ambiguity: there may be several of her devices with the calendar application

Complete the address withcontextual parameters from the network: where is she now? (synchronization is application dependent)


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“Place a meeting in the agenda of Yolande”•Address is as simple as possible•Ambiguity: are there preferences relating to scheduling of meetings? (phone, email, calendar, not now)

contextual parameters from the target: Right now, you should phone me

Complete the address with

Design The address is completed by context information: context supported addressing

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Notation

• Flexible enough to specify a variety of addresses

• Stringent enough to allow address checking and avoid unnecessary ambiguity

•Independent of technical details (network, availability)

•Independent of practical details (Location of the target, target’s preferences, …)

•Allows to ‘fill in’ contextual information

•Should be adaptable to the application’s type of requests

Addressing SchemeAddressing SchemeQuite intuitive:• Example address:

Agenda(a), <Yolande>.owns(a)

• Or more specific: Agenda(a), <Yolande>.owns(a), <Yolande>.headOf(<embedded>), <Yolande>.isMobile

• Other way of specifying this:Application(a), <Yolande>.supports(a), Application.type(a) == agenda

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Notation example

Addressing SchemeAddressing SchemeAgenda(a), <Yolande>.owns(a)

• <term>: system looks up what it means, depending on context

• Additionally, you can be more specific:Person(term) : the term is of type person

• Instances:Person(<Yolande>) y, y.fullname(“Yolande Berbers”),y.headOf(<embedded>)

• If ‘embedded’ is not further specified, from the context (Yolande, Koen) the system can infer: embedded group

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Notation example

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Coupling with the overlay network

• No explicit coupling with the overlay• However, the knowledge in the overlay

will determine the result of a request• Objects may be located but not able to

communicate• Objects may leave

• Therefore, there are 4 possible answers to a request:1. Network address / list of network

addresses2. Object not found, but address valid3. Object found, but not available4. Address not valid

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Mapping to the

overlay network

• Addresses can not be mapped directly to the overlay

• Search for objects and context specification used in the address using known search techniques• Inspect relations, compare to address• Search for context information needed

for the context reasoning

pda

phone

Second floor of CWPrinter p2a

CSS

Embedded Taskforce

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Overlay NetworkOverlay Network• Tasks:• Given a physical network network with

context aware devices: structure• Be able to provide one of the 4

answers• Optimize for searching

• Allow queries for every object or context information in the network

• Allow queries for associations between these objects or information (needed for reasoning)

• Connect & integrate new objects to the overlay

Fucti-onality

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Overlay NetworkOverlay Network• Build as a semantic network, using

associations between both context and objects

• Associations Semantic, Temporal, Spatial, Procedural Examples

• Spatial: CloseTo(A,B, distance) with distance Exact(20,m) or Fuzzy(visible)

• Semantic: isInterface(Interface#4864, SonyBravia#4864)

• Temporal: UsageFrequency(5 times / day, average)• Procedural: isRemoteFor([Remote#12,Remote #6864],

Interface#4864) Object or context information points to other objects

or context using associations. Following these pointers is equal to navigating

through the network

Design &

structure

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Overlay NetworkOverlay Network• Objects & context that has the same

association is grouped: context groups• Examples

5th floor in CW building (a) Printers in CW building (b) Computers with internet access (e) Objects that are accessed at least 2 times / minute

(c) All objects used by application X (d)

• Enpowers: Searching: (a) * (b) -> Printers on the 5th floor in

CW building Optimalisation: (c) * (d) -> Place all frequently

accessed objects near to application X Backup all objects used by X on another network (e)

Design &

structure

Overlay NetworkOverlay Network• Admission of objects / information to the

network Detect possible associations between the new

objects / information and the environment Make detected associations, join context

groups• Detection using adapted form of flooding:

context-aware flooding Format: object, distribution criteria,

max_hardhops, max_softhops Flooding bounded to relevant environment Reference to relevant objects is returned ->

possible association If object is relevant in large environment ->

new group candidate12/2007 2525

Design &

structure

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ArchitectureArchitectureApplication Layer

Context Supported Addressing

Context Reasoning

Search Algorithms

Inference & Decision Engine

Overlay Network

Presence Management

Searching Algorithms

Optimalisation, QOS

Persistence Management

Network Layer

Routing QOS Connection Management

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