requirement prioritization

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Vaatimusten priorisointi

Requirement Prioritization

Requirements Prioritization

Requirement Prioritization

Structure of the presentationIntroduction Prioritization principlesPrioritization methodsPrioritization scalesWiegers` methodPair-wise comparison techniqueComparison between the methods

Requirement Prioritization

Introduction (1/3)There are usually more requirements than you can implement given stakeholder`s time and resource constraints... [Kar97], but...

Requirement Prioritization

Introduction (2/3)... on the other hand, systems have useless functions for the users and customers!

Requirement Prioritization

If we manage to implement just those requirements that meet customer and user needsproduct development time shortensproduct development costs decreaseHow to select a subset of the customers requirements and still produce a system that meets their needs?

Introduction (3/3)

Requirement Prioritization

Requirements prioritization

Requirement Prioritization

Prioritization principles Prioritization means balancing the business benefit of each requirement against its cost and any implications it has for the architechtural foundation and future evolution of the product [Wie99]

Requirement Prioritization

Why prioritize requirements? (1/2)Priorities help youconcentrate on the most important user and customer requirementsfocus the development effortmanage projects more effectivelyplan for staged deliveriesIt can also help you make acceptable trade-offs among conflicting goalsallocate resources [Wie99], [Kar97]

Requirement Prioritization

Why prioritize requirements? (2/2)If the customers do not differentiate their requirements by importance and urgency, project managers must make these decisions on their own. [Wie99]Most software organisations carry out this selection process informally and quite frequently produce systems that developers, customers and users view as suboptimal. [Kar97]

Requirement Prioritization

Challenges of prioritization (1/2)Different stakeholders have usually different opinions about requirements importance and urgency.People naturally have their own interest and they aren`t always willing to compromise their needs for someone else`s benefit.Many of the prioritization methods are either too complicated and time consuming or insufficient [Rya97].

Requirement Prioritization

Challenges of prioritization (2/2)Customers may try to avoid prioritization, becausethey suspect that low priority requirements will never be implementedDevelopers may try to avoid prioritization, because they feel bad to admit, that they can`t implement all requirements

Requirement Prioritization

Prioritization methods

Requirement Prioritization

Prioritization scales (1/3)MethodGrouping requirements in the categoriesUsually three-level scale (e.g. Essential, Conditional, Optional [IEEE98])ParticipantsDifferent stakeholdersConflicts are negotiated informally

Requirement Prioritization

Prioritization scales (2/3)ProsCheap and easy to useClear technique, near common sense.

Requirement Prioritization

Prioritization scales (3/3)ConsThe results are in many cases just a rough estimate Participant dependent methodCustomers estimate 85% of requirements at high priority, 15% at medium and 5% at low priorityNo desired flexibility for the projectIn the real world low priority requirements have frequently been abandoned.

Requirement Prioritization

Wiegers method (1/4)Basic ideaCustomer value depends on both the benefit provided to the customer by spesific requirementpenalty paid by that feature [Par96]Can be used only for negotiable requirements (those that are not top priority)

Requirement Prioritization

Wiegers method (2/4)MethodEstimate for each requirement using scale from 1 to 9relative benefit that it provides to the customerrelative penalty the customer would suffer without itrelative cost for itrelative risk for itCalculate the percentage of the benefit/penalty/ cost/risk that comes from each requirement

Requirement Prioritization

Wiegers method (3/4)Calculate priority for each requirement using the following formula

ParticipantsKey customer representativesSoftware developers

Requirement Prioritization

Wiegers method (4/4)ProsRelative methodEstimation is based on several variablesResults are informative and clear ConsNot much objective information is available about the methodResults are dependent on peoples ability to estimate value, cost and risk

Requirement Prioritization

Pair-wise comparison (1/6)Methodn requirements are setted up in the rows and columns of the n x n matrixPair-wise comparison of all the requirements according the criterion from 1 to 9

Requirement Prioritization

Pair-wise comparison (2/6)

1Of equal value3Slightly more value5Essential or strong value7Extreme value9Intermediate value

Requirement Prioritization

Pair-wise comparison (3/6)ParticipantsRequirements engineersReview candidate requirementsCustomers and usersApply p-w comparison to estimate the relative value of the candidate requirements Software engineersApply p-w comparison to estimate the relative cost of implementing each requirement

Requirement Prioritization

Value (%)Pair-wise comparison (4/6)Cost (%)RequirementCost-value diagram

Requirement Prioritization

Pair-wise comparison (5/6)ProsReliable methodRedundancyInformative resultsEstimating relative values is found to be easier and quicker than estimating absolute values

Requirement Prioritization

Pair-wise comparison (6/6)ConsSuitable only for a small number of requirements (