8.2.5 Model Adaptability

The model-related issues we have discussed to this point are all rather concrete and relatively easy to address. Other, more subjective model attributes are also important, however. For an agency considering implementation of an existing model, a critical question becomes: Is this model adaptable to the articular agency's needs? For any agency contemplating long-term use of a model, an analogous question can be stated: Is this model flexible in ongoing use? This second question relates to whether the model can be adjusted to depict changes in operating policies that are bound to occur from time to time.

The importance of adaptability (generalizability) in transfer has already been discussed in the context of the M/M/N priority queueing model for police deployment. One city's standard operating procedure may be entirely unacceptable in another city. Even apparently subtle changes in operating policy can violate the theoretical underpinnings of an existing model (as any leader of Chapters 3-7 should be aware of by now!).

When trying to circumvent the transferability problem, one must naturally ask: "How much generality can I afford?" If a model is being funded internally, the model builder has no obligation to incorporate generalizability beyond that needed for the client city. If the model is being funded by a federal agency, more generality is certainly called for. However, even then there are limits, including those posed by analytical tractability as well as by costs.

Regarding ongoing use in a single jurisdiction, an agency's operating rules are likely to change over time. A prioritized response service may radically change its prioritization structure. A school district may split a 6 year high school into a 3-year junior high and a 3-year senior high. A bus company may introduce new types of vehicles. The question to the modeler To what extent will the model still be useful under various conceivable operating changes? The same comments made above about generalizability apply here. Surely no model should be so rigid that the most minor change in an agency's operating policies makes the model obsolete. The professional model builder should incorporate sufficient flexibility into the model design to allow for reasonable changes in operating rules that do not violate the cost constraints of model development and implementation.