©2006 BAE Systems. Practical Implementation of COSYSMO Reuse Extension Gan Wang, Aaron Ankrum, Cort Millar, Alex Shernoff, Ricardo Valerdi

Agenda Background Industry Definition BAE Systems Implementation Lessons Learned and Recommendations

What Is the Problem? Everything has a legacy In particular, most of the systems we build and programs we execute are based on legacy systems, architecture, and experience –Rarely are we building something completely new from the “clean slate”. Academic COSYSMO assumes all size drivers (Req, Int, Alg, Scn) are new, which is inadequate in estimating the systems we build today Therefore, we must consider the impact of reuse on systems engineering size We anticipate this will improve the model’s accuracy since reuse plays a significant role in today’s systems

COSYSMO at BAE Systems BAE Systems E&IS OG has developed an internal systems estimating tool based on COSYSMO –Collected 55 past program data points across lines of business and major sites –Developed platform-specific calibrations Problem encountered: Academic COSYSMO could not provide the correlation and convergence required to create meaningful calibrations –One of the big issues was driver reuse We worked with key stakeholders and developed the industry definition of COSYSMO Reuse We developed an internal implementation/instantiation of the reuse extension

Industry Definition

Reuse Categories 1.New: Items that are completely new. 2.Adopted: Items that are incorporated unmodified. 3.Modified: Items that are reused but are tailored. 4.Deleted: Items that are removed from a system.

Driver Counting Framework AdoptedModified New Deleted Easy Nominal Difficult # System Requirements # System Interfaces # System Algorithms # Operational Scenarios

Application of Reuse at BAE Systems

Implementation Strategy Be consistent with industry definition –By further instantiating and refining the verbiage so as to avoid any potential conflicts and inconsistencies Provide a clear and consistent operational guideline for driver counting and classification –By defining unambiguous verbiage of the reuse definition Establish clear boundaries between categories to ensure easy separation and consistency –Steps rather than ramps –Delineated by common concepts

Approach Define two (orthogonal) dimensions of classification framework to enable finer grain estimation of the size drivers: –Reuse by Process: SE activities –Level of Difficulty by Relative Effort: easy, nominal, difficult

Reuse Categories at BAE Systems 1.New: Items that are completely new 2.Managed: Items that are incorporated and require no added SE effort other than technical management 3.Adopted: Items that are incorporated unmodified but require verification and validation 4.Modified: Items that are incorporated but require tailoring or interface changes, and verification and validation 5.Deleted: Items that are removed from a legacy system, which require design analysis, tailoring or interface changes, and verification and validation Notes: New items are generally unprecedented Those items that are inherited but require architecture or implementation changes should be counted as New

Added Categories “Managed” We found, in particular, significant number of requirements require “technical management” level of effort only –They are still part of the system deliverables –They are still to be “sold off” to customers –They are not free Applied for –Proven elements from previous iterations/spirals –Subcontract/teammate provided turn-key components

Where: PM NS = effort in Person Hours/Months (Nominal Schedule) A = calibration constant derived from historical project data k = {REQ, IF, ALG, SCN} r = {New, Managed, Adopted, Modified, Deleted} w r = weight for defined levels of size driver reuse w x = weight for “easy”, “nominal”, or “difficult” size driver Ф x = quantity of “k” size driver E = represents diseconomy of scale CEM = composite effort multiplier Extended COSYSMO Relationship

Driver Classification Guideline NewManagedAdoptedModifiedDeleted Easy Nominal Difficult Second Pass Order of Classification Separate the two dimensions:  Apply reuse in terms of Process (activity)  Apply levels of difficulty in term of Relative Effort First Pass

Define Reuse Weights Based on Activities

Data Before Reuse Application

Same Data After Reuse Application

Excellent Correlation Achieved for Similar Programs PRED(30) PRED(25) PRED(20)

Application Lessons Learned Modified category, in particular, covers a wide range The intent of the modified category is to capture those elements that involve tailoring changes only, with no changes to the internal architecture If you modify everything, you should classify it as New Consistency is the key –Between data points –Between calibration data and new estimate What do we do for consistency? –Asked for a sample nominal requirement –Compare the productivity metric with peer programs –Graphical aids are helpful, e.g.,

Recommendations Reuse weights are meant to be defined ones only. Once they are defined, you should stick with it and apply to all programs –If you have to change them, apply to all program data Recommendation: industry should have a recommended value range for all reuse categories –To better communicate BOEs

Gan Wang Contact Ricardo Valerdi