EVALUATION OF FLEXIBLE POINTS ON USER INTERFACE

FOR INFORMATION SYSTEM

Limin Shen, Chunyan Gao and Wenwen Jiang

Department of Computer Science and Technology, Yanshan University, Qinhuangdao, China

Keywords: User interface, flexible point, flexible change, flexible degree, function point.

Abstract: To deal with user requirement changes at runtime, information system software provides adaptable

operations through user interfaces to change software functionality. We suggest the FleXible Point(FXP),

flexible changes, flexible degree, flexible force, and flexible distance, to evaluate the effect of such user

interfaces. Flexible degree is determined by flexible distance and flexible force. Flexible distance is

measured by function point counting and flexible force is measured by level value of flexible point. An

application to wage calculation software is given to illustrate the evaluation and measurement based on the

FXP. The approach can be used as a guide to adjusting, improving, and to comparing the FXP on user

interfaces, and arranging different levels of manipulators to increase the FXP efficiency and to bring the

FXPs on user interface into play.

1 INTRODUCTION

To deal with user requirement changes, some

software products provide adaptable operations

through flexible or intelligent user interface (UI).

We define such a point or a location on UI as a

FleXible Point (FXP), and define the changes

triggered and caused by the FXP as flexible changes.

What is flexible? Thesaurus

Dictionary gives the

following interpretations: “Capable of being bent,

turned, bowed, flexed repeatedly without breaking,

injury or damage; capable of being adapted;

responsive to change; adaptable”. Accordingly, the

flexible changes in software are controllable,

repeatable, inversed, consistent and harmonious.

The FXPs and flexible changes have made

software system more flexible and software can

change as user requirements change. How to

evaluate the effect of FXPs on UI and the flexibility

brought by them is to yet be clearly defined. We

present an approach based on the FXP and flexible

change to evaluate the effect of the FXP and its

flexibility brought by it.

2 RELATED WORK

In software engineering, software flexibility concept

had appeared in 1979. Pamas (1979) thought flexible

software is one that can be easily changed, extended,

contracted, or else in order to be used in a variety of

ways. Keith Bennett (1999, 2000) presented a list of

features about flexible software, suggesting that

flexible software should be necessary and sufficient,

personalized, adaptable and self adaptive, distributed,

in small units and transparent. Amnon

Eden (2006)

presented evaluating software flexibility from

program paradigm, architecture and design patterns.

Robin Jeffries (1991) suggested that a UI was

evaluated prior to its release by heuristic evaluation,

software guidelines, cognitive walkthroughs, and

usability testing.

However, most research in this area concentrates

on evaluation of UI design, usability and reliability.

Few research aims at providing a model that allows

discussing and expressing quantitative relations

between UI and software flexibility.

3 MEASUREMENT FACTORS

3.1 Changes via Force

To study how software can be changed, the “force”

concept is introduced. It is the force that pushes

software change. The force F consists of external

force F

and internal force F

, F =F

. The

internal force F

is given by software itself at

253

Shen L., Gao C. and Jiang W. (2007).

EVALUATION OF FLEXIBLE POINTS ON USER INTERFACE FOR INFORMATION SYSTEM.

In Proceedings of the Ninth International Conference on Enterprise Information Systems - HCI, pages 253-256

DOI: 10.5220/0002347002530256

 SciTePress

runtime; the external force F

is given by a

manipulator through a FXP. F is determined by

software internal structure, such as architecture style,

design pattern, framework, etc. F

is determined by

flexible and adaptive mechanism such as dynamic

binding, reflection and control platform, etc.

3.2 Definition of Concepts

The quantitative concepts are introduced as follows:

. Flexible Point FXP

: a point or a location on

the interface that can cause and trigger flexible

changes to occur, through which F

may apply.

. Flexible Force

: the minimum F

applied to

FXP

that may trigger software to change.

. Flexible Distance S

: the maximum range or

size of software change caused by

through FXPi.

. Flexible Degree

K : )1/(

iii

fSK

= , a

measure for software flexibility brought by FXP

. Flexible Capacity

∑

KCC

, a measure of

entire or partial flexibility brought by a set of FXPs.

4 ANALYSIS BASED ON FXPS

Software manipulators are divided into three levels:

Low-level User (LU), High-level User (HU) and

Developer-level User (DU). Their F

is F

, F

and

respectively, obviously,

DUHULU

FFF

≤

Whether a manipulator can utilize a FXP

determined by the fact whether F

f . The FXPs

can be distinguished into four levels based on the

relation between

and F

Self-Adaptive FXP (SAFXP): all FXP

with

, oriented to all users. The flexible capacity

brought by the SAFXP is

|0 (1)

SAFXP i i

CKf

∑

LU-oriented FXP (LUFXP): all FXP

with

LUi

Ff ≤<0

, oriented to the LU.

|0 (2)

LUFXP i i LU

CKfF

=<≤

∑

HU-oriented FXP (HUFXP): all FXP

with

HUiLU

FfF

≤

, oriented to the HU.

|(3)

HUFXP i LU i HU

CKFfF

=<≤

∑

DU-oriented FXP (DUFXP): all FXP

with

DUiHU

FfF

≤

， oriented to the DU.

|(4)

DUFXP i HU i DU

CKFfF

=<≤

∑

Related factors of the FXP have relations:

Implementation Difficulty (ID):

SAFXP

> ID

LUFXP

> ID

HUFXP

>ID

DUFXXP;

. Manipulation Easiness (ME):

SAFXP

> ME

LUFXP

> ME

HUFXP

>ME

DUFXP;

. Manipulator Cost (MC):

SAFXP

< MC

LUFXP

< MC

HUFXP

<MC

DUFXP

5 EVALUATION OF FXPS

The necessary measure steps of FXPs are as follows:

(1) Identify the FXP. (2) Calculate the FXP’s

flexible distance. (3) Determine flexible force value

of the FXP. (4) Calculate the flexible degree of the

FXP. (5) Calculate flexible capacity for different

analysis.

5.1 Identification of FXPs

Our initial investigation classified the FXP into five

categories. (1) The adjustment of input interface:

software users can customize or modify the input

manners, contents and formats, etc. (2) The

adjustment of output interface: software users can

customize or modify the output manners, contents

and formats. (3) The adjustment of business rules:

the users can maintain the business rules through

FXPs. (4) The adjustment of business flows:

according to the actual requirements users can adjust

the business flows. (5) The adjustment of data

structure and data source: users can select data

sources, and modify data structures, data ranges, etc.

The FXPs can be menu items, command buttons,

textboxes, drop-down-lists, tables, graphs, etc. For

general measurements, they only need provide

exercisable software and user instructions.

There are some FXPs instances often used on UI:

(1) adjust the value range of data element; (2) add

/delete business rules; (3) add/delete items in

selection; (4) add calculation formulas; (5)

add/delete information items; (6) adjust screen

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layout; (7) change data items type; (8) Select data

sources; (9) find services automatically or adaptively.

5.2 Calculation of Flexible Distance

We use function point count as unit of measuring

flexible distance S

. Function point counts can

represent the functional size of software in the users’

view, which have four main advantages as follows.

Firstly, it is easier to locate, identify and determine

the changes, for function point method classifies

software function into five components: EI (external

input), EO (external output), EQ (external inquiry),

ILF (internal logic files) and EIF (external interface

files). Secondly, we can directly use the rules given

by IFPUG. Thirdly, the function point analysis (FPA)

provides measurement rules for GUI. Finally, the

FPA is independent of platform and program

languages.

We adjusted the process of FPA for calculation

flexible distance as follows: (1) determine the

application boundary of the FXP; (2) identify and

rate transactional function types to determine their

contribution to the Unadjusted Function Point (UFP)

count; (3) identify and rate data function types to

determine their contribution to the UFP count; (4)

take UFP counts as flexible distance.

Table 1: Flexible force value of FXP.

FXP Level

Manipulation

SAFXP 0

No user’s manipulation

LUFXP 10 Simple functional manipulation

HUFXP 20 Functional and business manipulation

DUFXP 30 Average technical manipulation

5.3 Determination Flexible Force Value

The value of flexible force

is determined by the

FXP level. We defined the flexible force value of

self-adaptive flexible point is 0. The scale value of

each level is defined as 10. Because of f

SAFP

=0 and

SAFXP

< f

LUFXP

< f

HUFXP

DUFXP

, we can define the

flexible force as table 1.

5.4 Calculation Flexible Degree and

Capacity

Once flexible force

f and flexible distance

S are

gained, the flexible degree of FXP

can be calculated

by the formula

)1/(

iii

fSK

= . After each FXP’s

flexible degree is determined, it is time to calculate

different types of flexible capacity.

6 CASE STUDY

A Wage Calculation Software (WCS) has the

elementary functions: data input, data print, inquiry,

data import and data export. Meanwhile, the WCS

provides six FXPs, which are shown as the second

column on Table 3.

We proposed three implementation schemes. The

level of FXP in each scheme may be different,

which is indicated at column

. On Table 3, if

∞

f , it means the FXP does not exist.

In scheme 1, FXP

is a HUFXP, which is

suitable for HU to add or delete information items

such as address, e-mail, birth date, and calculable

items such as traffic allowance, worked hours

without modifying codes. At this point, the software

gives a relatively simple manipulation screen to the

end user. After users add or delete wage items, the

WCS is able to automatically adjust and change data

input interface, data output interface, and internal

logical files. Function point components EI, EO, EQ,

ILF and EIF are impacted and changed. While in

schemes 2, FXP

is designed as a DUFXP, it needs

developer’s intervention to satisfy requirements

above, and the flexibility at the FXP decreases, but

its implementation mechanism will be simple. In

schemes 3, FXP

does not exist, when the

requirements above change, users and the

maintainers have to change software codes.

We assume that prepared manipulators for the

WCS are LU and HU. Available FXPs (AFXP) are

FXPs which users have ability to manipulate.

The capacity of the AFXP in the case is

)5(

HUFXPP

FfKFfKC

LUFXP

HUi

iEi

iAFXP

≤=≤=

∑∑

Rate of FXP’s availability (RA) is

RA = number of the AFXP/ total number of the FXP (6)

Table 2 shows flexible capacity of every scheme.

Scheme 1 gains the highest flexibility and the

highest RA because prepared manipulators accord

with required manipulators. Inversely, scheme 3

gains the lowest flexibility and RA is 0. The data on

Table 3 and Table 2 can be used as quantitative

information to guide software developers and users

to improve the UI intelligence and software

flexibility.

EVALUATION OF FLEXIBLE POINTS ON USER INTERFACE FOR INFORMATION SYSTEM

255

Table 2: The calculation of flexible distance, flexible force and flexible capacity.

Scheme 1 Scheme2 Scheme 3

Flexible points FXP

Changed function

components

1 Adjust the wage item width EI, EO, EQ, ILF,EIF 56 20(HUFXP) 2.67 20(HUFXP) 2.67 30(DUFXP) 1.81

2 Add/delete wage item EI,EO,EQ,ILF,EIF 178 20(HUFXP) 8.48 30(DUFXP) 5.74

∞

Modify calculation

formulas

EO, ILF 29 10(LUFXP) 2.64 20(HUFXP) 1.38 30(DUFXP) 0.94

4 Adjust screen layout

EI 6 0(SAFXP) 6 20(HUFXP) 0.29 30(DUFXP) 0.19

5 Add calculation formulas

EO, ILF 30 20(HUFXP) 1.42 30(DUFXP) 0.97

∞

Adjust wage print table EO, EQ 12 10(LUFXP) 1.09 20(HUFXP) 0.57 30(DUFXP) 0.39

In the measurement process, we found that

though FXPs in scheme 3 were difficult to

manipulate, they were visible to the end user. Some

of the FXPs in scheme 1 are easy to manipulate but

they are hidden deeper and it is difficult to find

them. Thus the visibility of the FXP and its

manipulation difficulty have crucial influence on the

usability of the FXP. So, the metric should have

considered this issue.

Table 3: Analysis of WCS’ FXP.

Flexible capacity Scheme 1 Scheme2 Scheme 3

SA flexible capacity 6 0 0

LU flexible capacity 3.73 0 0

HU flexible capacity 12.57 4.91 0

DU flexble capacity 0 6.71 3.33

Available flexible

capacity

22.3 4.90 0.00

Available rate of

FXP

100% 42.25% 0.00%

* Manipulators are the LU and the HU

7 CONCLUSION

This is our initial investigation on evaluation of the

FXPs on UI. We put forward a new concept FXP,

built a measurement model with it, and summarized

how to quantify the FXPs. Though the measurement

can’t solve all the fundamental problems on software

flexibility, our work provides a new way to

understand and answer questions about software

flexibility.

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