263Validation
the pieces are built but must be repeated as interacting blocks are incorpo-
rated. Itis best if the testing is done by someone different than the person
constructing the model. Developers of software have elaborated detailed
approaches to completing this kind of verication, and there is an exten-
sive literature on the subject (Beyer 2014). The following sections address
common aspects of DES for HTA that should be checked as part of the
verication process.
The whole verication procedure should be carefully documented, includ-
ing what was tested, by whom, how it was tested, when, and what were the
results of the testing. In practical terms, an external assessor addressing this
aspect, after the model is completed, can only rel ...