Causal Graphs

These are a mechanism for formally describing possible failure cases in DNA. At the moment we have just looked at the screening process, identifying a couple of things which could have gone wrong, and how we would see these things.

This process does not offer any solutions, simply a mechanism for finding and identifying problems.

Here is an example:



This is a very simple example, which contains two mechanisms for detecting faults (detectors) and three possible faults. For an example, I will talk through the 'icy crystal' situation.

An icy crystal (i.e. with 'ice' forming on the surface) will cause curcular diffraction patterns on the image - ice rings. The symptom of an icy crystal is therefore ice rings on the diffraction pattern. These ice rings can exhibit their presence in three possible ways:
These indicators should therefore be able to clearly say that this problem occurred. These make use of two detectors, Mosflm and the DiffractionImage module. Without the DiffractionImage module it would not be easy to distinguish between this situation and others.

Clearly, in a non automated system there is a further detector, the user, and he or she may spot these possible indicators of failure.