The OAR Method

The Options Analysis for Reengineering (OAR) method is a systematic, architecture-centric approach for identifying and mining reusable software components within large, complex software systems. OAR addresses the following questions:

How does one efficiently and cost-effectively rehabilitate legacy software?
Which legacy components are worth extracting for reuse in a new software product line or with a new architecture?
What types of changes need to be made to the components?
What are the risks and costs involved in identifying and reusing legacy components?

The OAR method consists of five major activities with scalable tasks:

These activities have the following goals:

Establish Mining Context: understand the organization's product line needs, legacy base, and expectations for mining legacy components
Inventory Components: identify the legacy system components that can potentially be mined for use as product line components in core asset base
Analyze Candidate Components: analyze a candidate set of legacy components to evaluate their potential for use as product line components
Plan Mining Options: develop alternative plans for mining based on schedule, cost, effort, risk, and resource considerations
Select Mining Option: select which mining option or combination of options can best satisfy the organization's mining goals by balancing the programmatic and technical considerations

OAR enables users to screen candidate software components; identify the best candidates for reuse; analyze, isolate and aggregate candidate components; and estimate the level of difficulty, cost, and effort required to mine and rehabilitate the software components selected. Using OAR results, a reengineering team can focus its efforts on those high-value components that meet the technical and programmatic needs of the software product line or the new single system architecture.

Outputs of OAR include:

Inventory of existing legacy components and related documentation
Component Table identifying reusable components, their characteristics, estimates of changes needed, level of difficulty, estimated effort and cost
Options Table that identifies a set of mining options that reflects the organization's elicited needs, priorities, and concerns
List of product line or new single system components that can, and cannot, be satisfied by mining

For additional documentation, see:

Bergey, John; O'Brien, Liam; Smith, Dennis. Options Analysis for Reengineering (OAR): A Method for Mining Legacy Assets (CMU/SEI-2001-TN-013).
Bergey, John; O'Brien, Liam; Smith, Dennis. OAR: Options Analysis for Reengineering: Mining Components for a Product Line or New Software Architecture, presented at International Conference on Software Engineering, 2001 (ICSE, 2001); Toronto, Canada, May, 2001.