Page 273 - Software and Systems Requirements Engineering in Practice

ç ç 3 O F T W A R E ç ç 3 Y S T E M S ç 2 E Q U I R E M E N T S ç % N G I N E E R I N G ç ) N ç 0 R A C T I C E

%XPLORATORY PROTOTYPES ARE USED WHEN THE FUNCTIONALITY IS
EVOLVING OR BEING DISCOVERED DURING THE PROJECT !GILE APPROACHES SUCH
AS 3CRUM ;3CHWABER ET AL = MAY WORK WELL ON SOFTWARE PROJECTS FOR
SUCH SITUATIONS WHERE THE FUNCTIONALITY IS ADDED INCREMENTALLY 3CRUM
MAY BE APPLIED BOTH TO EARLY PHASE ACTIVITIES SUCH AS FOR RAPIDLY
DEVELOPING A THROWAWAY PROTOTYPE OR DURING IMPLEMENTATION WHERE
THE DEVELOPMENT IS BROKEN DOWN INTO MONTHLY SPRINTS

õ 7HENõTOõ0ROTOTYPE
2APID PROTOTYPING IS GENERALLY USED WHEN REQUIREMENTS ARE NOT WELL
UNDERSTOOD AND THERE IS A NEED TO BETTER UNDERSTAND WHAT THE
ENVISIONED PRODUCT WILL DO E G BY VIEWING THE USER INTERFACE 4HE
PRIMARY GOAL OF PROTOTYPING IS TO ANSWER SPECIFIC QUESTIONS REGARDING
THE TARGET SYSTEM AND IN DOING SO TO DECREASE THE COMPLEXITY AND RISK
INVOLVED IN ITS IMPLEMENTATION ,ACK OF CLARITY ABOUT WHAT THE SYSTEM
SHOULD DO EITHER DUE TO ITS NOVELTY OR DUE TO STAKEHOLDER CONFLICTS OR
DUE TO A SHIFTING COMPETITIVE LANDSCAPE INCREASES THE COMPLEXITY AND
THE RISK THAT SIGNIFICANT CHANGES WILL BECOME NECESSARY IN LATER STAGES
OF THE DEVELOPMENT LIFE CYCLE
7E RECOMMEND PROTOTYPING AS A GOOD WAY OF QUICKLY EVOLVING
FROM FUZZY HIGH LEVEL REQUESTS TOWARD REALISTIC AND VIABLE SYSTEM
AND FEATURE REQUIREMENTS 0ROTOTYPING IS COMMONLY USED AS A WAY TO
VALIDATE TECHNICAL SOLUTIONS OR TO EXPLORE AN UNKNOWN PROBLEM OR
ENGINEERING DOMAIN 0ROTOTYPING IS ALSO USED VERY WIDELY THROUGHOUT
ENGINEERING AND MANUFACTURING ORGANIZATIONS TO VALIDATE FUTURE
PRODUCTS OR PRODUCTION PROCESSES )N MANY CASES SOFTWARE PROTOTYPING
IS A LOWER COST ALTERNATIVE TO PRODUCING REAL PHYSICAL PROTOTYPES AND
SOFTWARE PROTOTYPES ARE OFTEN SUFFICIENT FOR REPRESENTING MANY
FUNCTIONS
&ORMAL REQUIREMENTS INSPECTIONS COUPLED WITH PROTOTYPING ARE
EFFECTIVE IN REDUCING REQUIREMENTS DEFECTS ;*ONES = (OWEVER
THE SIZE OF PROTOTYPES BECOMES AN ISSUE SEE THE FOLLOWING h0ROTOTYPING
AND 3IZEv SIDEBAR )F THE SIZE OF THE PROTOTYPE IMPLEMENTS LESS THAN
ABOUT PERCENT OF THE TOTAL APPLICATION THE PROTOTYPE CANNOT
REPLICATE MANY OF THE KEY FEATURES "UT FOR VERY LARGE SYSTEMS IN ABOUT
THE FUNCTION POINT RANGE A PERCENT PROTOTYPE WOULD BE A
MAJOR SYSTEM IN ITS OWN RIGHT 4HEREFORE PROTOTYPING BECOMES LESS
EFFECTIVE FOR VERY LARGE APPLICATIONS SUCH AS %20 PACKAGES IN THE
FUNCTION POINT RANGE ;*ONES =
3OME EXAMPLE AREAS WHERE PROTOTYPING SUPPORTS REQUIREMENTS
ENGINEERS ARE GIVEN UNDER THE HEADINGS THAT FOLLOW
%ARLYõ2EQUIREMENTõ%LICITATION
4HE INITIAL REQUIREMENT ELICITATION FOR PROTOTYPING TASKS IS GENERALLY
SIMILAR TO THE APPROACH OF MANY AGILE METHODOLOGIES 4HE TASKS MUST
BE STRUCTURED AROUND SPECIFIC SCENARIOS OF INTEREST AND IN THE CONTEXT