WHAT, WHY AND HOW TO INTEGRATE

Self Organization within a SOA

Hakima Mellah

Research Center in Scientiﬁc and Technical Information, Cerist, Ben Aknoun, Algiers, Algeria

Salima Hassas

Liesp, Lyon 1 Univeristy, Lyon, France

Habiba Drias

USTHB Univeristy, Algiers, Algeria

Keywords:

SOA, Self Organization, MAS, Agility.

Abstract:

The main point of this work is to show how to contribute to information system (IS) agility by enabling

self-organization of distributed IS that represent the nodes of information network relating these IS. The con-

tribution is focused on presenting some factors that lead and trigger for self organization in a Service oriented

Architecture (SOA) and propose how to integrate Self Organizing(SO) mechanism as this latter has already

been proposed(in another work) for a Multi Agent System(MAS).

1 INTRODUCTION

Nowadays Companies are faced with an increasingly

complex environment where requirements of speed

and effectiveness determine their competitiveness.

An agile enterprise is a company with an information

system synchronized with its business (MIBS, 2006;

Syntec, 2007; McCoy and Plummer, 2006). The re-

sources in terms of services offered by its informa-

tion system (IS) may extend beyond the borders of

the business using transit interfaces such as Internet.

These interfaces can be used to interact with a vari-

ety of companies (other organizations) to request their

services. Inversely an organization providing any ser-

vice is often called upon to interact with a group of

services seekers (Benatallah et al., 2002; Mellah et al.,

2006). However a service can be changed and may

evolve over time (Macella and Pernici, 2006); a new

version of a service can be used in place of the old

one. During organizations interaction process, new

ones may integrate into this latter and offer new ser-

vices with advanced features. The main purpose of

computing services is to create the foundation tech-

nology and management required to support the en-

terprise agility (Zhao et al., 2007). To ensure this

agility and allow use of services, in order to meet

the business process and the user, it is important to

have a service-oriented software architecture (SOA)

(Zhao et al., 2007; Syntec, 2007). During the inter-

action, the meaning carried by information is related

to the information itself, to the manner it is used and

its relationship to other information in the same con-

text or the same information network. This is even

more important when a range of distributed and inter-

connected information sources is considered. The

complexity theory provides a conceptual working en-

vironment, a way of thinking and a way of seeing the

world (Cachon et al., 1999; McKelvey, ; Mitleton-

Kelly, 2003) or just the information. This new ap-

proach requires new connections and is to see a new

function (Cachon et al., 1999)for a portion of an en-

tity spatially located. We look at the organization as a

complex evolving system, co-evolving (Cachon et al.,

1999)with a social ecosystem. Complex systems are

multidimensional systems and all dimensions interact

and inﬂuence each other. Self-Organization (SO) is

a key feature of these systems. In an organizational

context it can be described by the spontaneous ar-

rival of a group for executing a task or reaching a

goal. The group decides by itself what to do, how and

when, without any external entity decision (Mitleton-

163

Mellah H., Hassas S. and Drias H. (2010).

WHAT, WHY AND HOW TO INTEGRATE - Self Organization within a SOA.

In Proceedings of the 12th International Conference on Enterprise Information Systems - Software Agents and Internet Computing, pages 163-167

DOI: 10.5220/0003018901630167

 SciTePress

Kelly, 2003). Emerging properties, patterns or struc-

tures appear from individual elements interactions. In

(Mellah et al., 2008) a representation model of dis-

tributed information sources is proposed and the in-

formation is structured in a three dimensional system

taking into account content, use and structure. The

contents that characterize an information source are

also used for one or more uses, themselves in rela-

tion with other uses and other contents that are re-

lated with a structure or an informational network.

Despite the potential of SOA to align business and

enterprise information technology, SOA still exhibits

a set of characteristics that make it complicated to

apply self-organization to an SOA-based system(Lei

et al., 2008). In (Lei et al., 2008) a reference architec-

ture is proposed to enable controlled self-organization

in a service-oriented environment. The distributed

and heterogeneous characteristics of service-oriented

computing demand for comprehensive management

approaches. In the mentioned architecture, self-

organization of SOA elements is achieved by a sep-

arate management overlay observing and controlling

the underlying SOA layer. It is also expected that the

architecture should be controlled by external policies

supplied by human system participants. This kind of

self organization is criticized by Gasser as it is men-

tioned in (Mellah et al., 2006).

2 SELF ORGANIZATION WITHIN

A SOA

Service orientation promotes a new way to design and

implement large scale distributed applications across

organizational and technical boundaries. However, it

does not provide sufﬁcient means to cope with the in-

creasing complexity in service-oriented applications.

A promising way out of this dilemma is to enable self-

organization in service oriented computing (Lei et al.,

2008). Using service orientation in the architectural

design facilitates reusability, ﬂexibility, interoperabil-

ity, and agility of this kind of systems. Generally, ser-

vice autonomy raises the question of how to establish

proper operation status on the system level(Lei et al.,

2008), especially in presence of possible failures in

some service elements. Self-organization means the

process of generation, adaptation and change of orga-

nizational structure. The latter is the result of indi-

vidual choices of a whole of entities to begin in inter-

action in certain organizational diagrams. We should

not determine the behaviour of a complex system but

rather, one has to expect new possibilities. Thus, we

will be able to adapt when the unforeseen ones ar-

rive, because we will be ready to expect unforeseen

(Mellah et al., 2006). This deﬁnition applies also

to the many facets of self organization called self-x

properties (Schmeck, 2005). For example, a system

is self-healing, if it can eliminate the effects of mal-

functioning units without needing for this corrective

action any external assistance. Obviously, this re-

quires the capability to detect deviations from the cor-

rect functionality of the system on a global or local

level(Schmeck, 2005). Nevertheless, in nature many

examples exist related with robust systems, are ob-

served as being able to provide certain functionality in

a completely self organized way. Therefore, there is

some hope that methods observed in natural systems

might be transferable to technical systems. Among

them we quote ant colonies and bacteria colonies. The

latter has been adopted to propose a self organizing

protocol based on multi agents system (Heylighen,

2003).

2.1 Choreography versus Web Services

Organization

The W3C (W3C Glossary) deﬁne orchestrations as

”the model of interaction that must comply a Web

service agent to achieve its goal”. However, even

if orchestrations are a support for incremental pro-

gramming in response to the introduction of a new

event or the coordination with a new service, they

do not support their own composition(Peltz, 2003)

. While orchestration describes, in terms of service,

interactions it may have with other services, and in-

ternal stages of data processing or invocations of in-

ternal modules(Peltz, 2003), choreography describes

the collaboration between services collection, whose

aim is achieving a given objective. The achieve-

ment of this objective is done by exchanging mes-

sages (Austin, 2004). Therefore, in choreography it

is possible to have multiple orchestrations and in each

one, one service will act as an orchestra chef. In

(Mellah et al., 2006) organization functioning inﬂu-

ences much it’s structuring; its key factors are the ele-

ments which form part of it: tasks and activities, com-

petences and responsibilities, interactions network as

well as the bonds, which connect these elements. In-

stead of considering information sources connection,

we consider the whole of WS that are choreographed

to respond to a user request. These WS translate exis-

tence of a discovery structure. As in an organization,

an SOA basic elements (WS), constituting a discovery

structure, are connected by varied and complex ﬂows

which are all signiﬁcant. They explain how the dis-

covery process has been achieved, or which services

are implied and composed relatively to the user query.

The complex ﬂows represent the organizational struc-

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164

ture and choreographed services are mapped to this

organizational structure’s elements. The interactions

networks connect the organizational positions (geo-

graphical positions on which services are located).

The information network must be self organized in

this context.

3 WHY IS IT IMPORTANT TO

INTEGRATE SELF

ORGANIZATION IN A SOA?

In services discovery process, information retrieval

includes two orthogonal components (Mellah et al.,

2006) which must be complementary and that are:

- The construction of the network: is a self-organizing

process which requires an adaptive behaviour while

respecting the network consumption;

- Research: is ensured by a distributed algorithm

which will exploit the structure of the emergent

network.

In (Mellah et al., 2006; Heylighen, 2003) a trigger

factor for self organizing distributed information

sources is IS response time, which can avoid a failure

production in the whole system. IS may encapsulate

services interact for responding to a user query. The

encapsulation will be based on a service discovery

structure that needs to maintain its connectivity

(between services). While interacting, and in order to

avoid resources bottleneck or single points of failures,

services components or resources should maintain

connectivity with each others. This connectivity

can be assured by the recourse to self organizing

resources or services components. Services fault

causalities are varied and three main categories are

distinguished (Erradi, 2006): (i)Functional faults that

are caused by a non completion of task execution

or some incorrect results delivered by service (for

example: price limits or delivery deadline),

(ii)Environmental faults that refer to communication

infrastructure exceptions and middleware failures of

the hosting servers and database servers (for example:

service response time, service availability).

(iii)Contractual fault that are linked to the violation

of service level agreement (SLAs) and collaboration

policies; in this case the service execution might be

completed without the conformity of results to the

negotiated SLAs.

In this paper, we emphasize more on the second

category, and delayed service response time or non

service availability when:

-machines or network connections of a particular ser-

vice provider are currently overloaded. The infor-

mation may inﬂuence an agent to choose a different

provider offers the same or a similar service.

-a transaction was involved by a user, such as the

provider identity and network locations of speciﬁc

services within a composed service, we should avoid

situation like resource bottlenecks or single point of

failure within the network.

The quoted points are few factors to explore about the

discovery of the required service(s). These can be

triggered elements, dealing exactly with service dis-

covery self organization within a SOA.

4 HOW SELF ORGANIZATION

CAN BE INTEGRATED IN A

SOA

To be able to integrate self organization within an

SOA, we ﬁrst consider the mapping between chore-

ographed services and the organizational structure’s

elements, and then we will try to adapt self organi-

zation within services itself. In (Chan et al., 2006),

a general approach in system fault tolerance that can

be applicable to WS is proposed, based on a repli-

cation driven WS system and on a replication man-

ager. The replication manager keeps check the WS

availability by the polling method. All the check-

ing process is centralized on the replication manager

and its abstract process. If the latter does not re-

spond any more what will happen to the whole sys-

tem? In (Ardissono et al., 2007) a WS monitor is

charged of checking the choreographed services by

receiving their status messages during choreography.

The problem is also posed when the WS monitor it-

self does not respond in time. Several other proposals

are supporting the development of reliable composite

web services, in centralized WS orchestration (Ardis-

sono et al., 2006). In decentralized orchestration, the

state of the composite WS depends on its distribution

across nodes. Human based approaches, to discover

and utilize services, is not only time consuming, but

also requires continuous user interaction. Software

agents have been subject to research in many inter-

related ﬁelds. They are long-lived, having persistent

computations that can perceive reason, act, and com-

municate. They have the ability to make decisions in-

dependently, without human intervention and without

inﬂuence from other agents, notably when they are

some failures during the service discovery process.

Chaﬂe (Ardissono et al., 2006)proposes a framework

based on local monitoring agents for checking the

WHAT, WHY AND HOW TO INTEGRATE - Self Organization within a SOA

165

state of the orchestrated WS, and interact with a Sta-

tus Monitor. Palathingal and his colleagues (Palan-

thingal and Chandra, 2004) developed a multi agents

approach for service discovery and utilization. In this

approach there is no indication on the adopted inter-

action protocol, while agents interact, or on failure

production within the system. The most concrete ex-

ample of a self organization is the way in which the

ants produce pheromone like traces between the food

sources. Thus, the food sources are organized in ef-

fective network of provisioning ways. Marco Dorigo

(Gershenson and Heylighen, 2003) is a pioneer in the

ﬁeld of ant algorithms. The Bacteria colonies also re-

organize by forming patterns in order to ﬁght against

the adverse life conditions, of the environment. They

develop a sophisticated co-operative behaviour and

complex possibilities of communication, in order to

be able to change their pattern and thus to reorganize,

like the direct cell-cell physical interactions by the in-

termediary of additional membrane polymers, which

is useful for the model formation in ”without-life”

systems. Based on these models, we have elaborated

a communication model (Mellah et al., 2006) and a

self organizing protocol (Mellah et al., 2007) based

principally on communication primitives that show

how, through interactions (communication), interact-

ing information sources are self organized. Moreover,

the latter is regarded as an interaction cellular pro-

gram and complexity is ensured by the composition

of blocks (primitives). In (Mellah et al., 2008) despite

the model, a layered architecture is proposed for dis-

covering contents of distributed IS, and the ﬁrst layer

that interacts with users, is based on agents. For this,

we suggest the recourse to a Multi Agent Systems

(MAS) self organizing protocol for service discovery

process. The self organizing protocol is inspired by

bacteria colony life.

5 WHAT IS TO BE SELF

ORGANIZE IN A SOA

In Palathingal’s (Palanthingal and Chandra, 2004) ap-

proach, the proposed MAS is within the UDDI. When

a service provider expresses the need to publish ser-

vices, an agent is created. Each software agent is

specialized in a category of services. In the pro-

posed approach solicited in this paper, the proposed

MAS for services discovery is based principally on

data duplication, which is inspired from (Palanthingal

and Chandra, 2004; Erradi, 2006), within the services

provider. Therefore, instead to affect a provider of

services to a single machine,services are duplicated

on several machines and at each one, a software agent

is associated. At each provider will correspond sev-

eral machines. When a service does not respond any

more or there is a resource bottleneck, another ma-

chine will be ready to provide the same or similar ser-

vice. Based on these postulates, services will be con-

sidered as the tasks transferred between agents ma-

chines. The latter’s interaction will be based on the

self organizing protocol proposed in (Mellah et al.,

2007), and failures are detected by the checking prim-

itive that keeps alive interactions between agents ma-

chines (ﬁgure1). The positioning primitive states the

distance between agent machines that do not responds

to a service request and on which data are duplicated;

the routing primitive elaborates the way to follow for

reaching the required service from other machines.

After ﬁnding the addresses, the new service will be

updated within the WSDL document. It will be also

interesting to extend the MAS approach, for contexts

providers, and resolve the same failures problems en-

countered, additionally with contexts.

Figure 1: Emergence of a new services communication

structure by the mean of the MAS AO protocol.

services are duplicated on several machines and

at each one, a software agent is associated. At each

provider will correspond several machines. When a

service does not respond any more or there is a re-

source bottleneck, another machine will be ready to

provide the same or similar service. Based on these

postulates, services will be considered as the tasks

transferred between agents machines. The latter’s in-

teraction will be based on the self organizing protocol

proposed in (Mellah et al., 2007), and failures are de-

tected by the checking primitive that keeps alive inter-

actions between agents machines (ﬁgure1). The po-

sitioning primitive states the distance between agent

machines that do not responds to a service request

and on which data are duplicated; the routing prim-

itive elaborates the way to follow for reaching the re-

quired service from other machines. After ﬁnding the

addresses, the new service will be updated within the

WSDL document. It will be also interesting to ex-

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166

tend the MAS approach, for contexts providers, and

resolve the same failures problems encountered, ad-

ditionally with contexts.

6 CONCLUSIONS

In this paper we have presented some challenging sit-

uations showing how and where to combine self or-

ganizing solutions with a SOA based systems, and

what a MAS self organizing protocol can bring to a

SOA. The proposed MAS self organizing protocol is

inspired form bacteria colony. As perspective we are

trying to assure services discovery process based on a

self organizing MAS. The MAS will be integrated in

a layered architecture combining agents and services

technology.

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