Flexibility Concepts

CHAPTER I CHAPTER I INTRODUCTION

2.1 Flexibility and Online Airline Reservation Systems

2.1.1 Flexibility Concepts

to changes in the environment" [42]. In case of manufacturing, one may distinguish eleven different classes of flexibility: machine, material handling, operation, process, product, routing, volume, expansion, program, production and market flexibility [43]-

(45]. In the discipline of systems engineering, the flexibility of a system is understood as "the ability to respond to change" [ 46]. Product design literature defines flexibility

"as the ability of companies to frequently upgrade their products to meet the rapidly changing technologies" [47], (48]. Each of the above definition defines flexibility in a different perspective, but the fundamental meaning of this term remains consistent across all definitions which: "able to flex."

As defined by the Special Interest Group on Human-Computer Interaction (SIGCHI) of the Association for Computing V!achinery (ACM) "Human Computer Interaction is a discipline concerned with the design, evaluation and implementation of interactive computing systems for human use and with the study of the major phenomena surrounding them." In HCI, human actions are processed by computers;

as a result interaction occurs between the two. This shows that humans make computer perform operations, therefore, it is very important to understand human computer interaction in the context of flexibility as well. Hence, flexibility can be discussed from these two different perspectives, i.e. (I) System's Flexibility (Computer) and (2) Users' Flexibility (Humans) as shown in Figure 2.1.

System's Flexibility

I

User's FlexibilitY]

Figure 2.1: Two Different Perspectives of Flexibility

2.1.1.1 System's Flexibility

Within the HCI discipline, System's Flexibility is referred to its ability to respond to internal or external changes. However, th<: ambiguous characteristic of word

"flexibility" [46] has forced authors to explain flexibility differently as shown in Table 2.1.

Human computer interaction studies are conducted to develop or improve the safety, utility, etlectiveness, efficiency. usability, appeal of the systems that include computers as shown in Figure 2.2. Of which, Usability of the systems is described by researchers as a "measure of the ease with which a system can be learned and used, its safety, effectiveness and efficiency, and attitude of its users towards it" [49]. While, ISO defines Usability as "the extent to which a product can be used by specified users to achieve specified goals with effectiveness, etliciency and satisfaction in a specified context of use" (ISO 9241-11 ). The principles that provide support to achieve, develop or improve Usability of the system include, (I) Learnability, which is the ease with which users can use the system effectively. (2) Robustness, which is the level of support provided to the user to achieve its goals and (3) Flexibility, which is basically multiplicity of ways the user and the system exchanges information.

Table 2.1: Definitions of Flexibility in the Context of System Engineering Author

Nilchiani

Saleh

Ross

Definition of Flexibility

We define flexibility as the ability of a system to respond to potential internal or external changes affecting its value delivery, in a timely and cost-effective manner. Thus, flexibility is the ease with which the system can respond to uncertainty in a manner to sustain or increase its value delivery. It should be noted that uncertainty is a key element in the definition of flexibility. Uncertainty can create both risks and opportunities in a system, and it is with the existence of uncertainty that flexibility becomes valuable.

Flexibility should be sought when: I) the uncertainty in a system's environment such that there is a need to mitigate market risks, in the case of a commercial venture, and reduce a design's exposure to uncertainty in its environment, 2) the system's technology base evolves on a time scale considerably shorter than the system's design lifetime, thus requiring a solution for mitigating risks associated with technology obsolescence.

The only difference between flexibility and adaptability is the location of the change agent with respect to the system boundary: inside (adaptable) or outside (flexible). Of course the system boundary could be redefined, changing a flexible change into an adaptable one, or vice versa. The fungible nature of the definition is often reflected in colloquial usage and sometimes results in confusion. If the system boundary and location of change agent are well- defined, confusion will be minimized.

Reference

[50]

[51]

[52]

0.'\.'\.~ HCI Constructs

Y-'-'~~~~"..~~~~~~"

Safety Utility

Figure 2.2: Different Elements of Human Computer Interaction

Of the three principles, Flexibility is related to taking input/output in different forms and examined with respect to (I) Dialogue initiatives, (2) Multi-threading, (3) Task migratability, (4) Substitutivity and (5) C:ustomizability as shown in Figure 2.3.

Customizability refers to adaptability of interfaces to suit different needs, and it is achieved by way of (i) adaptability, where users can adapt the user interface, (ii) adaptivity, where the user interface can be adapted by the system and (iii) personalization, where the user interface is tailored towards the individual user. While system driven interaction hinders its flexibility, user-driven interaction is considered to be strongly favourable.

Dialogue Initiative

Multi Threading

I

Leamability

l

Task Migratability

~

Flexibility

I

~

^Usability

Adaptability Substitutivity

I

Robustnous

J

Adaptivity Customizability

Personalization

Figure 2.3: Flexibility as the Multiplicity of Ways for Information Exchange

2.1.1.2 Users' Flexibility

The User's Flexibility is nothing but users' ability to rapidly change from one course of action to another, i.e. "flexible behavior", and it is referred as a hallmark of human

cognition system [53]. Webster's Dictionary defines cognition as "the act or process of knowing in the broadest sense; specifically. an intellectual process by which knowledge is gained from perception or ideas". Empirical research into cognition is usually scientific and quantitative, and involves formation of mental models to describe or explain certain behaviors. In context of t1cxiblc behavior of users, human cognition system may thus be examined from the perspective of cognitive psychology. As mentioned earlier, Human-Computer Interaction (HCI) research is intended to explain interaction between humans and the computer technology. And in order to provide a scientific explanation to human behavior (e.g. user interface design, information visualization, etc) many principles, theories and concepts from cognitive psychology are deployed in HCI [54]-[60] such as Perception, Categorization, Memory, Knowledge Representation, Language and Thinking as shown in Figure 2.4.

L

Perception Categorization

Memory

Co~n-;;~

l

Psychology ¹

Logic I

j I L::::e_ __ ^j

,.I

^Thinking

--~

I_

Decis~~~aking

Problem Solving

Figure 2.4: Building Construct of Cognitive Psychology

Thinking refers to any intellectual or mental activity resulting m ideas or arrangements of ideas and within the context of HCI. thinking simulates human behavior, which is eventually translated as an action taken on part of users, in the form of making choices, performing logical operations. formation of concepts, problem solving and decision making [61]. For understanding t1exible human

behavior, decision making is an important reflection of users thought process.

Decision making is a mental process which results in selection of a course of action among several alternatives. At the end of every decision making process, an output is produced in the form of a final choice or selection, which can be in the form an action, or an opinion of choice. Decision making process is an active research area since it examines decisions of users in context of their unique set of needs and preferences, therefore, reflection of users' Hexible behavior can be seen in the decisions they make [62], [63].

2.1.1.3 Conceptual Linking between System's Flexibility and Users' Flexibility

In order to understand users' Hexible behavior, it is first important to understand the contexts that govern users' behavior towards being flexible. In case of System's Flexibility, users interact with computer systems in order to accomplish tasks. While the System's Flexibility is reHected in its customizability features, therefore, developing an understanding of system's customizability in terms of affecting users Hexible behavior, requires a science base in the form of systematic knowledge of what governs user's Hexible behavior' and inHuencing upon their decision making process as shown in Figure 2.5. Thus, three variables have been identified in this basic conceptual framework: (i) System's Flexibility, (ii) Users' Flexibility and (iii) System's Usability.

From literature review, it is found out that users' flexible behavior is reflected in their decision making process, while Syst,~m's Flexibility is translated in its customizability features.

I. System's Flexibility has a linear relationship with User's Flexibility due to the following assumptions:

• A Hexible system (customizable) can reinforce users' Hexible behavior by inHuencing upon their decision-making, even if they were inHexible or partially Hexible initially [25].

• On the contrary, if a user is flexible with respect to making decisions, it cannot still reinforce System's Flexibility through customizability, even if it was inf1exible or partially flexible, initially.

2. System ·s Flexibility is one of the principles that provide support to achieve, develop or improve usability of the system. System's flexibility thus has a linear relationship with System's Usability.

3. Users' flexible behavior in terms of their decision making influence upon the usability of a system. Thus Users' Flexibility has a linear relationship with System's Usability.

Adaptability

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Personalization

Dialogue lmtiattve

Multi Threading

Task Mtgratabiltty

Substitutivity

{ Customuobility

)1-System's Flexibility

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Users' Flexibility

Cognltivo

P•yc~ology (~ht~~;ng) J

A

Chol<e . -]

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Logic

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[con<ept Fonn,.ion : D«l•ion Making 1 Problem Solving

Figure 2.5: Conceptual Linking between System's Flexibility and Users' Flexibility From literature it is concluded that flexibility can be discussed from two different aspects, one from System's perspective (Computers), and second from User's perspective (Human). System's Flexibility translates into its customizability in achieving the defined usability objectives of the system which are effectiveness, efficiency and satisfaction.

Likewise, in context of User's Flexibility, this section concludes that different users may have different needs, interests and wishes to be served and system's

effectiveness, efficiency and satisfaction may vary from one user to another based on their usability perception. For some users a sys1tem may be very effective but this may not be true for all. This drives the need of integrating cognitive ergonomics into the framework, to understand Users' Flexibility in designing of systems. Moreover, from literature it is found that Users' Flexibility is ret1ected in their decision making behavior. Further elaboration and validation of the conceptual linking between System's Flexibility, Users' Flexibility and Usability can be found in the methodology chapter Section 3 .2.1.