Page 274 - Software and Systems Requirements Engineering in Practice

A
P

ç
$
I
D
ç
H
A
E
S
E
R
P
T
E
E
C
ç
4
H
Q
U
N
I
L
O
V
E
P
N
T
M
E
ç ç # # H A P T E R ç ç ç 2 2 A P I D ç $ E V E L O P M E N T ç 4E C H N I Q U E S ç ç
OF SPECIFIC USER TYPES 7HEN THE REQUIREMENTS ARE DISCUSSED IN THE
PROBLEM DOMAIN THE END USERS ARE MUCH BETTER ABLE TO REASON AND
COMMUNICATE USEFUL INFORMATION ABOUT THE BUSINESS GOALS CONSTRAINTS
AND PRECONDITIONS THAT THEY PERCEIVE 4HE FUNCTION OF THE DESIRED
FEATURES OF THE PRODUCT MUST BE PUT IN CONTEXT OF THE AGREED UPON
SCENARIOS IN ORDER TO BE CONSIDERED IN THE PROTOTYPING PROCESS
/NCE SPECIFIC SCENARIOS ARE IDENTIFIED WITH SOME AGREEMENT ON
THEIR PRECONDITIONS AND CONSTRAINTS THE NEXT STEP IS TO INTRODUCE
CANDIDATE USER INTERACTIONS 4HESE CAN COME FROM THE DOMAIN EXPERTS
AND BE BASED ON THEIR KNOWLEDGE OF EXISTING SYSTEMS IN THE MARKET
OR AVAILABILITY OF REUSABLE OR STANDARDIZED COMPONENTS $EVELOPERS
AND DESIGNERS CAN OFTEN SUGGEST ALTERNATIVES BASED ON THEIR
EXPERIENCE WITH EXISTING OR EMERGING TECHNOLOGIES )NTERACTIONS CAN
BE DEFINED AT MULTIPLE LEVELS BOTH AT A HIGH GRANULARITY DESCRIBING
LONG RUNNING INTERACTIONS AND AT A LOW LEVEL DESCRIBING THE
INTERACTIONS OF INDIVIDUAL USER CONTROLS
/NCE THE SCENARIOS ARE DEFINED WITH SPECIFIED CONTEXT AND USERS
THEY ARE PROTOTYPED IN A LIGHTWEIGHT FORM 3UCH PROTOTYPES CAN BE
REVIEWED BY THE STAKEHOLDERS PROVIDING A STABLE BASIS FOR ACCEPTING
OR REJECTING SPECIFIC USER INTERACTION DETAILS AND FOR FORMULATING
SPECIFIC CHANGE REQUESTS #ONTINUING WITH A SIMPLE REPRESENTATION OR
PROCEEDING TO AN EXECUTABLE PROTOTYPE THEN BECOMES A DECISION ABOUT
OPTIMIZING THE PROGRESS BASED ON THE QUALITY OF REPRESENTATION AND
THE PROTOTYPING EFFORT 3OME BENEFITS OF USING PROTOTYPING IN THE
CONTEXT OF REQUIREMENTS ELICITATION WERE QUANTIFIED IN THE INDUSTRIAL
CASE STUDY DESCRIBED IN ;6ERNER ET AL =
#ONFLICTING OR .ONPRIORITIZED 2EQUIREMENTS
4HERE ARE MANY POTENTIAL CONFLICTING STAKEHOLDER REQUESTS THAT WILL
ARISE AS A NEW SYSTEM IS BEING DEFINED 4HERE ARE INEVITABLE CONFLICTS
BETWEEN THE LOCALIZED INTERESTS OF INDIVIDUAL STAKEHOLDERS AND THE
OVERALL INTERESTS OF THE ENTIRE ORGANIZATION #ONVENTIONAL TEXT BASED
REQUIREMENTS REPRESENTATIONS MAY PROVIDE INADEQUATE SUPPORT FOR
CONFLICT DETECTION AND RESOLUTION
-ODELING OF SYSTEM REQUIREMENTS PROVIDES A BETTER ANALYSIS
INFRASTRUCTURE TO BE USED FOR DETECTING AND RESOLVING CONFLICTS
PARTICULARLY IF THE MODEL IS SUFFICIENTLY FORMAL TO ALLOW CERTAIN
AUTOMATED CONSISTENCY CHECKS (OWEVER THIS STILL MAY NOT SOLVE THE
PROBLEM BECAUSE DOMAIN EXPERTS AND STAKEHOLDERS MAY NOT BE
PROFICIENT IN THE MODELING TECHNIQUES USED BY SYSTEM ARCHITECTS AND
DEVELOPERS !S SUCH DOMAIN EXPERTS AND STAKEHOLDERS MAY BE UNABLE
TO FULLY UNDERSTAND THE PROPOSED SYSTEM AS IT IS BEING PRESENTED AND
THUS MAY NOT BE ABLE TO IDENTIFY CONFLICTS OR ERRORS
7E CAN USE PROTOTYPES TO EXECUTE UNAMBIGUOUS REPRESENTATIONS
OF RELATIVELY COMPLEX USER SCENARIOS FOR THE SYSTEM "Y INCORPORATING
SOME SCALE AND COMPLEXITY INTO THE PROTOTYPES WE EXPOSE MORE
STAKEHOLDERS TO A HIGH LEVEL VIEW OF THE SYSTEM AND ENABLE THEM