Step 3: Compound Scoring. For each library compound identified as a potential match for a target m/z, we compute several reference metrics that can be used to support the presumptive identification of the target. Since its initial publication, there have been several subtle changes in the scoring and presentation of scores. For ease of reading, we will discuss two subtle data preprocessing steps that occur prior to scoring, and a major philosophical change in the presentation of computed scoring metrics. A separate summary of each scoring metric is provided in Table .