Estimate the restricted model and write down the log-likelihood, lnLr. If the log-likelihood function were retrievable within the program, there would be no need to employ outside resources such as a calculator or a pencil and paper. Retrievability brings a second, less obvious requirement. There must be some means of using the result once it is retrieved. For the example above, for the log-likelihoods to be useful in further computations, it must be possible to do the computation in Step 3.
Programs do differ in the degree to which one can post-process results.
Consider, for example, carrying out a Hausman test on a subset of the coefficients estimated by two different estimators. This operation would require 1. These require a considerable amount of flexibility. What is referred to above as post-processing' is the use of these estimation results in subsequent commands to analyze data in the context of a particular model, an extension of the model, or some general modeling framework.