The Testing —PREDICTOR

Testing of hypothesis is necessary if the ontcome of the construction phase is not uniqne. The program PREDICTOR consists of a series of production rules defining the theoretical behavior of a compound in the mass spectrometer. These rules are applied to each candidate strncture prodncing a hypothetical mass spectrum, which is compared to the experimental mass spectrnm. The rules used for the prediction phase are similar to those in the construction phase but are more generic. They use a proposed structure to derive potential fragmentation patterns. 

This is accomplished by creating the parent ion from the structure candidate and storing it in an ion list. The production rnles are applied and lead to a series of ionic strnctnre fragments that are appended to the list. In the next step, fragmentation is predicted for each ion, and a hypothetical mass spectrum is created and added to a spectrnm list. The spectrnm list contains the ion and the mass and charge value and its relative abnndance. The relative abundance is required since the same ion may occnr mnltiple times as resnlt of fragmentation of different substructures. If all ions in the ion list are compnted, the spectrum list contains all data for the hypothetical mass spectrnm of the candidate structure. 

A prodncfion rnle consists of a condition or an expression that has to be evaluated, and of an action that is triggered as a resnlt of the condition evaluates to true. Examples for conditions are 

FIGURE 6.1 (a) The matrix representation of molecules in the PREDICTOR system of the 

Any LISP function or any other production rule can be triggered. 

---