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A Framework for Software Product Line Practice, Version 5.0

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Make/Buy/Mine/Commission Analysis

In "A Note on Terminology", we pointed out that software enters an organization in one of three ways: it can be

Software that is built in-house can actually be constructed anew or mined from software already in the organization for use in a new effort. Every piece of software that is part of a development effort arrived as the result of an all-encompassing four-way choice that we call "make/buy/mine/commission." Organizations that build software systems must all make this choice, but they usually lack a conscious rationale for their selection. The purpose of this practice area is to both underscore the necessity of making a conscious and reasoned choice and describe some of the analyses that can help an organization make the right choice.

Techniques from the discipline of decision analysis apply well here. Decision analysis is the process of applying analytical methods to decision making in situations where there is uncertainty, multiple conflicting objectives, or dynamic change [Clemen 1991a, Hammond 1999a]. Such a situation exists when an organization is trying to choose the best way to obtain software and must, as a result, weigh several business, technical, and political factors. In such a case, making the decision requires both qualitative and quantitative analysis.

Sometimes the decision is straightforward. For some organizations, all the software assets are developed in-house for proprietary (or political) reasons. For other organizations, all the assets are commissioned because of organizational policy or because of unique requirements and a lack of in-house development resources. (In the U.S., most government organizations, such as the DoD, fit into this category.) If no other organization but yours has the necessary domain expertise in a component's realm, "buying" and "commissioning" are not viable alternatives. Conversely, if you have neither the skill nor the history to build a component, "making" and "mining" are not going to work. More commonly, however, some of the software will be built from scratch, some will be mined, some will be purchased on the open market, and some will be commissioned.

The make/buy/mine/commission decision for software is based on strategic factors such as the cost, schedule, staff availability, and expected quality and fitness of purpose that each alternative offers. For example, mining is valuable only when a project that uses the mined assets can be completed on time at a lower cost and produce a capability equal to or greater than that of comparable assets obtained through other means. Any calculation of reuse cost should include the total cost of use over the lifetime of the new product or products, not just the cost of mining/restoring a particular set of assets. In practice, improvements on one of the scales (at a cost to the others) may produce a significant tactical advantage. For example, if mining and restoration gain time but lose cost and functionality (relative to building from scratch), they could still provide a significant advantage if time to market is a primary driver. The direct cost of each alternative is a factor, but so is the opportunity cost: what could your staff be doing instead of building a component if you buy or commission it? If you developed it in-house, what could you do with the funds you would save by not employing an expensive contractor? If the staff is underused, the "make" and "mine" options get more weight. If the staff is overused and the schedule is tight, the "buy" and "commission" options get more weight. Other factors influence the decision when a service-oriented approach is used. For example, are suitable service providers available to offer the necessary types of services in a form that is compatible with the product line architecture? Will it be possible to sign a service level agreement (SLA) with particular vendors to guarantee the quality of service (QoS) needed for the product line?

When analyzing the

The make/buy/mine/commission decision for software should also be based on a frank assessment of an organization's own capabilities. Establishing working relationships with contractors can be tricky, and the legalities of drawing up an ironclad contract can be formidable for those without experience. If your organization does not have a standing legal department for which such relationships are pro forma, you might be better off on the "make/mine" side of the equation–that is, unless building such a capability for the future makes strategic sense for your organization. Conversely, if your development capabilities are weak, letting others tackle the technical complexities may be the best approach–again, unless you are trying to improve your organization's development skills or domain expertise. In either case, start your venture into the unknown with small steps, using the newest approaches for only the least critical components. In addition, have contingency plans to handle major missteps along the way.

Also keep in mind that the four options are not always mutually exclusive-for a given asset, you might do a little of each; for example

Since the make/buy/mine/commission decision analysis can be complex, making the decision consciously and documenting the rationale is a good idea.

Aspects Peculiar to Product Lines

The analysis approach for a product line is similar to that for single systems but with two main differences. When a product line is involved, you must perform the analysis (1) while constantly considering the satisfaction of the product line's production constraints and strategy and (2) using different weighting factors because of the reasons described below:

The decision analysis for a product line must also look further into the future for multiple products that will be spawned, each having its own lifetime. In a product line, much more is riding on the decisions about how and where to obtain software. Analysis is essential, and rigorous analysis is warranted.

Application to Core Asset Development

Because all core assets have to come from somewhere, make/buy/mine/commission analysis is at the root of core asset development, and the analysis applies to non-software assets as well as software assets. The possibility of commissioning entire swaths of product line development (such as domain analysis, scoping analysis, market analysis, requirements engineering, and testing) should be considered. Requirements, architectures, and designs–as we describe in the "Mining Existing Assets" practice area–are superb candidates for recovery and rehabilitation from previous systems. The criteria to consider during the analysis include

The source of the product line architecture must be chosen prior to, or at least concurrent with, deciding how to obtain individual component or service assets. The architecture, by definition, specifies constraints for component and service assets-constraints that must be factored into any analysis about how those assets will be obtained.

Application to Product Development

Individual products in the product line may need additional software not contained in the core asset base. The same decision analysis process should be used to determine how to obtain this software. The criteria may be less demanding if the component or service in question will not be a candidate for inclusion in the core asset base. Although the component or service would still need to align with the product line architecture, it wouldn't have to offer the variability needed to support other products. On the other hand, the cost of obtaining the component or service may be more of a consideration because it has to be absorbed by a single product rather than being amortized over a family of products.

For example, if there isn't a human-computer interface (HCI) component or subsystem in the core asset base and a specific product needs one, the product builder can select the HCI component that is optimal for the needs of that particular product and the allowable budget. On the other hand, if an HCI component would be a viable candidate for addition to the core asset base, the decision analysis would rely on the same criteria used for core asset development, as described above. Furthermore, if external services are to be used within an individual product, the cost of using these services must be considered.

Example Practices

Breadth-first analysis of options: One approach is to adopt a breadth-first strategy in which each of the four options for obtaining software is considered and explored before any is eliminated. For some options, the consideration may be trivial. For example, if organizational policy dictates the commissioning of all software systems, the "make" choice requires no consideration: it's simply not an option.

Example questions for analyzing the make/buy/mine/commission decision are given below. First, there is an umbrella set of questions for the breadth-first strategy, followed by four sets of specific questions–one for each of the four options. Since each organization is unique, these sample questions should be viewed as a starter set that you can customize and augment as necessary.

Umbrella questions that follow the breadth-first strategy:

After this initial analysis, the choices may be narrowed to two, three, or even one of the four major options. A more detailed analysis for each option still in the running could include questions such as the following:

Sample questions for the "make" option:

Sample questions for the "buy" option:

Sample questions for the "mine" option:

Sample questions for the "commission" option:

These question sets are meant to be starter sets. Weigh these factors according to your organization's needs and experience, and augment them with factors of your own.

OAR/SMART: The SEI Options Analysis for Reengineering (OAR) approach is used to make decisions on mining assets for product lines and to address the specific mining questions outlined above [Smith 2002a]. OAR is explained in more detail in the "Mining Existing Assets" practice area. Similarly, the SEI Service-Oriented Migration and Reuse Technique (SMART) helps organizations analyze a legacy system to determine whether its functionality, or subsets of it, can be reasonably exposed as services in a service-oriented architecture (SOA) [Lewis 2005a]. This technique may be useful if a service-oriented approach is used within a product line. Economic models such as SEI SIMPLE (discussed in the example practices for the "Building a Business Case" practice area) can help answer questions regarding the relative costs or cost savings of each option.

In some cases, the "commission" option may involve commissioning a supplier to mine assets from an existing system. Bergey and colleagues suggest that under these circumstances a specific set of practices should be included to

Tool support: Although spreadsheets are the most common tool used in decision analysis, tools that are more sophisticated are also available on personal computers. For example, TreeAge Software offers tools called DATA and DATA Interactive [TreeAge 1999a]. With DATA, an analyst can build sophisticated decision models as decision trees, influence diagrams, or Markov processes and then analyze them using analysis tools such as sensitivity analysis, cohort simulation, and Monte Carlo simulation. A companion product, DATA Interactive, provides a model customization and delivery system for accessing and analyzing the decision models created in DATA. These tools require knowledge about decision analysis principles, the problem domain, and the tools' functionality for building and analyzing models.

Practice Risks

Do not confuse the risks of this practice area with those of the practice areas associated with each of the four options (i.e., "Component Development," "Using Externally Available Software," "Mining Existing Assets," and "Developing an Acquisition Strategy"). The risks of this practice area are related to choosing among those options.

The major risk specific to this practice area is, of course, choosing the wrong option, which can result in inappropriate assets and undue direct (or opportunity) costs. This risk could occur for the following reasons:

Further Reading

[Clemen 1991a] & [Hammond 1999a]
Clemen, Hammond, Keeney, and Raiffa provide excellent background reading in decision analysis, which is necessary for applying the "Make/Buy/Mine/Commission" practice area successfully.

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