A Mechanism for Managing and Distributing

Information and Queries in a Smart Space Environment

Sergey Boldyrev, Ian Oliver and Jukka Honkola

Nokia Research, Itmerenkatu 11-13, 00180 Helsinki, Finland

Abstract. Distributed information management, especially when related to mo-

bile devices with their particular connectivity and computing needs is complex.

Based on notions of stability of information respository and factors such as com-

putation resources and connectivity we can optimise the distribution and querying

of said information across multiple mobile and other distributed devices.

1 Introduction

The modern communications era has brought about a tremendous expansion of wireless

networks. Various types of networking technologies have been and are being developed

resulting in unprecedented and increasing expansion of computer networks, television

networks, telephony networks, and other communications networks. As new network-

ing technologies evolve, consumer demand continues to fuel increased innovation with

respect to utilization of networks. Wireless and mobile networking technologies con-

tinue to address related consumer demands, while providing more ﬂexibility and imme-

diacy of information transfer [1–4].

As the ﬂexibility and functionality of mobile communications devices increases,

options for networking technologies continue to evolve. For example, the technology

associated with dynamic distributed device networks or dynamic architecture networks,

such as smart spaces, are becoming increasingly practical due to the evolution of mobile

communications devices.

A smart space may be an environment where a number of devices may use a shared

view of resources and services to access information within the environment [10]. In

this regard, smart spaces can provide improved user experiences by allowing users to

ﬂexibly introduce new devices and access most or all of the information available in the

dynamic multiple device environment from any of the devices within the environment.

However, problems with information management and message routing in smart

spaces can arise because smart spaces do not have a static network topology. As a re-

sult, difﬁculties arise with determining the location of desired information and/or the

presence of intended recipients in the network. Further, the prediction of efﬁcient paths

for routing messages, such as requests for information in the smart space can also be

problematic since the connectivity and the topology within the smart space cannot be

assured.

In this paper we address the issue of distributing information and queries over that

information and speciﬁcally the mechanisms that we have employed within our infras-

tructure for realising this.

Boldyrev S., Oliver I. and Honkola J. (2009).

A Mechanism for Managing and Distributing Information and Queries in a Smart Space Environment.

In Proceedings of the Joint Workshop on Advanced Technologies and Techniques for Enterprise Information Systems, pages 145-153

DOI: 10.5220/0002193101450153

 SciTePress

2 Background

The Smart Space infrastructure shown in ﬁgure 1 shows our implemented architecture.

The key points are that of the node, smart space and Semantic Information Brokers

(SIB).

There exist numerous, individual Smart Spaces in which persons, groups of persons

etc can place, share, interact and manipulate webs of information [11,12] with their own

locally agreed semantics. A review of such systems can be found in [13]. To interact

with and apply reasoning to these Smart Spaces and there information contained therein

we are required to construct processes which have access to that information - typically

these are known as nodes - we also use the term agent interchangably depending on the

context, but in this discussion we stick with the term ‘node’. Nodes are either personal

in that they perform tasks either directly decided upon by the user or autonomously for

or on behalf of the user, monitor particular situations or reason/data-mine the existing

information.

A space is represented by a number of Semantic Information Brokers each contain-

ing query and connectivity engines, a store for the information - we have standardised

on the use of RDF for this and a deductive closure mechanism over the store. Infor-

mation is distributed over the SIBs according to local policy (described in this paper)

but any node connecting (via a SIB) to the space sees only the total of all information

contained withini the space, ie: if a space is constructed out of a set of SIBs B, ∆ being

the deductive closure over the space and i(b) being the information contained in each

SIB then an node will see the information as described in the equation below:

β∈B

∆(i(β))

This implies that the SIBs are totally routable in order that all information is accessable

via any SIB. Additionally within a space, even those the deductive closures are com-

puted locally to a SIB the set of rules for deductive closure is the same for all SIBs

within a given space.

Nodes access information through the SIB to the Smart Space. The SIB operates as

a single entity in managing a Smart Space. However, as it stated in [5–7], the infras-

tructure can be distributed. The SIB can be formed by set of more than one SIB which

represents the Smart Space.

Fig.1. Smart Space SIB/Space/Node Architecture.

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This is done in a way that all SIB can receive all messages arriving at any SIB and

all messages passed on by the SIB appear to come from a Smart Space. Infrastructure

presupposes communication between any of SIBs which form one single Smart Space.

Such communication is performed by means of the adaptive designation of a SIB “mas-

ter” in any given Smart Space, throughout the Smart Space evolution as shown in ﬁgure

2. To leverage the abstraction of SIBs addressing, the IDs (keys), are used to identify

each message session to determine whether a SIB should process a particular message

of not. These keys are used to identify which SIB is in charge for processing which

message type and is also used for the workload balancing over all SIBs.

Fig.2. Smart Space Evolution.

This solves the problem of distributing information and queries in a consistent manner

across multiple computation elements making up the information processing system of

a SmartSpace. Furthermore,the issue of computing the deductiveclosure of information

at run-time is possible. Marking in terms of priority and stability level of the individual

processing elements such that queries can be distributed such that the most efﬁcient

processing of the query is made with the most stable set of information.

Stability factor is constructed from the connectivity controller information, where

the SIB is running, any additional valuable environment information. As an example

the Stability factor can be represented in folowing form:

= C + Idiv

+ P RL

where S is the stability factor for j-th SIB entity of any i-th device, C is connectivity

weight provided by connectivity controller, Idiv indicates how information is diverging

in the sense of query satisfaction, and PRL is optional cumulative power/reliability/laten

cy function provided by the particular device.

As it is shown the Stability factor is a result of superposition between information

which is provided by the intelligent connectivity controller, e.g. physical means which

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form computing environment, and Information management infrastructure [9]. Intelli-

gent connectivity controller is aware of its surrounding environment in addition to its

local connectivity capabilities. It may also be aware of the physical limitations and of

individual devices within the wireless range or [11] within the wired network is asso-

ciated. The aim of the interface provided by the controller to the distributed framework

component is to provide enough yet abstract connectivity properties of the devices par-

ticipating in to the distributed network. In addition the controller hides the complexity

of multitransport control mechanisms as a connectivity cost function interface.

Relationship between Stability factor and the Strategies shapes any stable (reliable)

distribution between several SIB entities, e.g. distributed SIB. The Stability factor is de-

ﬁned in tight connection with the strategies that form the distributed solution feasible.

Several strategies are considered:

1. to distribute query around all instrartucture, and, to put insert/retract on any stable

SIB

2. to distribute inserts/retracts around all infrastructure, and, to put query on any stable

SIB

3. any balancing strategy between listed above

SIB is stable if its operational parameters produce Stability factor as above a certain

threshold, thus room for real-time optimisation exists.

A Smart Space is actually constructed from a number (at least one) SIB which con-

tain the aforementioned schedulers, management information, listeners and information

store. A Space is represented by these SIBs: the total possible connectivity methods is

given by the distributed union of all the representing SIB listeners.

SIBs communicate internally to ensure that membership and credentials of the

Nodes that have joined that Space - they may connect via any listener and any SIB

in that Space. From the point of view of any Node, the information available is always

the distributed union over the transititve closure of the routes between all the SIBs -

the SIBs contain routing tables to other SIBs and within a Smart Space all the SIBs are

totally routable but not necessarily totally connected.

3 Considerations

We take into consideration the following:

1. Optimal distribution mechanisms and policies

2. Distributed query mechanisms

3. Optional mechanism based upon distributed inserts/retracts

There are three message groups which are used to provide distributed infrastructure:

management, store (subscribe, cancel subscribe) and query (query, deliver).

The distributed infrastructure management messages are used to keep correct neigh-

bour descriptors and incremental routing tables and are used to support store and query

messages. They are the basic elements of synchronisation protocol between any of the

SIBs. The incremental routing table maintained to handle a Neighbours list. There are

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following maintenance messages, Join/Leave, HB (heartbeat, including timeout), Send,

Notify and Forward. There is a cache for previously constructed routes, thus messages

can be routed directly, without lookup within the distributed infrastructure. To inform

about connectivity parameters of any SIB instance the HB (Heartbeat) message is used.

To navigate around the SIBs two lists are constructed and used, the ﬁrst is based on

Neighbours list and is in charge of any successor routing, the operation is simple Send.

The second list can be used to improve overall performance and leverage the workload,

that list is exponentially distributed IDs of all other SIBs.

Store group are used to pass information to the SIBs and to operate with them. They

are Insert and Remove, provide distribution of the information. Query message (below)

presents the way of distribution which is applicable to Store group messages.

The Query group is used to pass the query to the SIBs for any particular information

as well as subscriptions to the SIBs and to operate with them. They are Subscribe and

UnSubscribe, provide distribution of the persistent queries. Query message presents the

way of distribution which is applicable to all Query group messages. The Query mes-

sage can be routed to any other SIBs. The Query message can be forwarded by any

other SIBs according to the incremental routing table, ﬁnger table and routing decision.

In case of message forward, notiﬁcation is generated by SIB and is used to override

routing decision. Such decision is obtained by means of network conditions. Thus the

query tends to pass SIBs only once. Therefore the query route construction converges

to the efﬁcient query forwarding mechanism. The result for Query group is passed by

means of Deliver message, which returns particular information.

SIB has managing responsibilities to form the SIB distributed infrastructure. Such

managing SIB is denoted as mSIB instance, the master SIB. There can be more than

one mSIB. Each SIB should have stability factor. In negotiation of any two SIB the

SIB with highest stability factor is selected to be mSIB. Stability factor is a result of

superposition between information which is provided by the intelligent connectivity

controller, e.g. physical means which form computing environment. Intelligent connec-

tivity controller is aware of its surrounding environment in addition to its local con-

nectivity capabilities. It may also be aware of the physical limitations and of individual

devices within the wireless range or within the wired network is associated. The aim

of the interface provided by the controller to the distributed framework component is

to provide enough yet abstract connectivity properties of the devices participating in to

the distributed network. In addition the controller hides the complexity of multitrasport

control mechanisms as a connectivity cost function interface.

In a very beginning, a SIB or the SIBs should establish the SIB distributed infras-

tructure by sending a Join message as shown in ﬁgure 3.

Such Join message contains an authentication part, [1] When the mSIB receives

this Join message it checks it with authentication mechanism [1] and if it fails it tells

the newcomer that Join has failed. If the mSIB does succeed with newcomer authenti-

cation it sends conﬁrmation to Join message. When the conﬁrmation to Join message

received then the SIB is conﬁrmed SIB distributed infrastructure member.

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Fig.3. Smart Space, join procedure.

4 Description

Since the SIB distributed infrastructure management is driven by the Heartbeat message

exchange, each SIB has timer to track these Heartbeat messages. The events whether

the SIB received Heartbeat message from mSIB or any neighbour SIB within a certain

period of time are tracked.

Regarding mSIB to SIB interaction, there are several cases when the SIB should

execute Join the SIB:

- If the timer expires, no Heartbeat message is received in a given period of time will

mean that the mSIB is down and the SIB should Join the SIB distributed infrastructure

again.

- If it gets Quit message, SIB should leave the SIB distributed infrastructure

If the SIB sending Join message doesn’t have a conﬁrmation message this SIB broad-

casts messages offering to become the mSIB. If the SIB gets “mSIB exists” message

this SIB tries to Join again with preserved stability factor. If after the SIB broadcasts

the packets offering to become the mSIB, it gets no response within predetermined

amount of time, it sends broadcast responses to inform everyone in SIB distributed in-

frastructure about new credentials and from now on acts as the mSIB of SIB distributed

infrastructure. If there is response from mSIB, and if the stability factor is above the

threshold to become mSIB, it sends broadcast responses to inform everyone in SIB dis-

tributed infrastructure about new credentials and from now on acts as the mSIB of SIB

distributed infrastructure.

If during the process of mSIB handover as shown in ﬁgure 4, the SIB has no no-

150

tiﬁcation that another mSIB exists and is thinking that it is the only mSIB but keep

receiving Quit message, the SIB must return and try to Join again.

Fig.4. Smart Space, handover procedure.

During the lifetime due to the ﬂuctuations of the stability factor of any SIB, including

current mSIBs, and, due to involuntary faults, the managing functionality can migrate

to any other SIB.

There are three main approaches to maintain the infrastructure (chained by stability

of the distributed infrastructure, it means that each stage represents maturity of the

infrastructure and is used by controllable takeover mechanism):

1. all Smart Space members, SIBs, are able to see all packets and applies incremental

routing technique to forward the message to the appropriate Smart Space member,

SIB

2. mSIBs are managing and determining the packets to be send and forward to the

appropriate Smart Space member, SIB

3. when SIB routing mechanism has query update capabilities, then this method is

used. It is the case when routing technique is extended by the local information that

particular SIB can provide [9]

The mechanism of determination which Smart Space member is to process a message

and allow other to disregard the message is based on incremental key routing [6].

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5 Discussion and Conclusions

Our approach intelligently utilises stability factor calculation based on the information

management approach [9]. Therefore, it serves as leveraging information dissemination

throughout the balanced query/insert/retracts. Tracking the most relevant requests of

the information through the scalable, energy efﬁcient mechanism. Whole approach efﬁ-

ciently utilises different computing platform, though some complexity in computations

exists.

This approach can also be applied to improve the fault-tolerance of the space as a

whole to information loss. While not our targetting focus this particular area provides

many suitable ideas which are being explored.

Acknowledgements

This work has been partially funded as part of the TEKES ICT SHOK DIEM (www.

diem.ﬁ) project.

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