Size Estimation in ERP Projects

by marc 22. december 2010 06:37


Difference ERP vs non-ERP

          Non-ERP: make your use cases etc. Estimate on a use case basis

          ERP: basic functionality already available, making usecases not seen as useful…


ERP: use available components as metric objects




What is available at the end of Inception phase?

          Highlevel Business Process

          Highlevel Business Requirements

          Global Impact Analysis                

          Use Case Model

          Architecture Description

And because you chose ERP

All documentation/experience/knowledge of that ERP





Proposal for Metric Objects in ERP projects

Classify business process

        New: New business process (not implemented in ERP before)

        Modified: Business process implemented in ERP but with modifications

        Re-use: Business process implemented in ERP without processmodifications


Classify Standard & Custom components

        New: components to be developed because COTS application does not provide for required functionality

        Modified: components to be modified because COTS application already contains (standard components but these do not entirely meet the requirements

        Re-use: pre-existing software will be used, but needs to be tested and integrated with new and modified components





Detail level

Classification business process

        Clear link to process-model tool must be used

Classification COTS components

        ‘Chunk of functionality’ within ERP-module: Receipts, Payments etc

        Independent functioning customization: 1 Interface, 1 report


      Detail too low: ERP module Accounts Payable

      Detail too high: Individual form, parameter for report



Find Agreement on classification

          Classification done individually by

        Business keyusers

        Supplier – application consultants

        Supplier – customization consultant





          Together agree on complexity per businessprocess

        Per businessprocess count

      Nr of new components

      Nr of reused components

      Nr of modified components

        Result is: estimation points. A number (like function points) which gives:

      indication of expected effort needed for a businessprocesses

      Indication of complexity of a businessprocess in relation to the other businessprocess (relative weight).



How to use the results to refine estimates?

First use own experience on how many hours per point


Ask supplier to report (weekly) on hours spent per business process in elaboration phase.

This gives an indication of the hours needed in elaboration phase per process identified in the impact analysis.

Supplierdeliverables in elaboration phase can be linked to businessprocesses from the impact analysis. Therefore reporting on hours spent per process should not be a problem.


Future projects can be used to refine this.




          Do not treat it as a science

          Try to find the most suited variable for your situation

          Use more then one estimating technique

          Just do it!



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