You will have read some articles, stopped by vendor booths in exhibit halls, and perhaps requested literature and general cost information from vendors whose products look interesting; but it is the OR that will be the cornerstone of your evaluation process. Thus, if possible, try to wait until you have received all or most vendor responses and have had the opportunity to give them an initial look-through before taking the next step, which is to schedule system demonstrations. By so doing, you will avoid having to look at a system that is eliminated early in the evaluation process either because the vendor chose not to respond or because the response was 'fatally flawed.'