## 4 Materials and Methods
### Diagnostic Process
\begin{table}
\begin{tabular}{l l l} \hline \hline \multicolumn{1}{l}{**(Sub)Category**} & \multicolumn{1}{l}{**Parameter**} & \multicolumn{1}{l}{**Type**} \\ \hline \multicolumn{1}{l}{**Environmental**} & & \\  & Temperature & numeric \\  & Average weight & numeric \\  & **External Clinical** & **Signs (Symptoms)** & \\ Behavioral & Anorexia & boolean \\  & Lethargic fish & boolean \\  & Weight loss & boolean \\  & Reduced weight increase rate & boolean \\  & Swimming Bladder Control Loss & boolean \\  & Stress & boolean \\  & Mortality & Categorical (zero, massive, nonmassive) \\  & Swimming Behavior & Categorical (normal, alien, slow, fast) \\  & Time between symptoms and deaths & Categorical (normal, small, large) \\ Physiological & Skin color darkening & boolean \\  & Skin discoloration & boolean \\  & Whitisation areas & boolean \\  & Conjugal fins redness & boolean \\  & Retinopathy & boolean \\  & Exophthalmos & boolean \\  & Corneal Clouding & boolean \\  & Mouth lower jaw deformity & boolean \\  & Corrosion-Necrosis of Tail and Fins & boolean \\  & Scales Loss & boolean \\  & Bleeding areas & boolean \\  & Hemorrhagic and necrotic lesions & boolean \\  & Hemorrhagic stomatitis & boolean \\  & Skin ulcers & Categorical (no, small, mild, large) \\  & Fins and Tail ulcers & boolean \\  & Soliosis or Lordosis & boolean \\  & or Hypercalcification & Release of Mucus Fecal Casts \\ \multicolumn{1}{l}{**Internal Clinical Signs (Symptoms)**} & \\ Gills & Excess gill mucous & boolean \\  & Gill discoloring & boolean \\  & Anemic gills & boolean \\  & Local changes & boolean \\ INTERNAL & Pseudoenteritis & boolean \\ Organs & Splenomegaly & boolean \\  & Granulomatosis & boolean \\  & Inflamed liver & boolean \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Parameters/Symptoms of sea bass diseases elicited from experts. Based on the above remarks and the way different categories of parameters were used in the decision trees, we concluded to use a level-based diagnostic process. So, we distinguish four levels of the diagnostic process (see Figure 4). At the _1 st Level Diagnosis_, only the environmental parameters (i.e., water temperature and fish average weight) are considered. They are quite crucial parameters whose values can exclude some diseases for further investigation. So, after the 1 st level diagnosis, a reduced number of diseases are passing for consideration at the next level diagnosis. At the _2 nd Level Diagnosis_, the external clinical symptoms are considered, distinguished in _behavioral_ and _physiological_ terms (Table 3). The user gives as input information about the observed external symptoms and/or their values (depending on the type of the symptom). In some cases, the user may provide an image of a fish, and the system calls the _image recognition unit_ (see Section 2.4) to automatically extract the required information. The output of this level is a list of possible diseases, ordered from the most probable to the least probable. The number of diseases may be further reduced. At the _3 rd Level Diagnosis_, the internal clinical symptoms are considered, distinguishing between _gills_ and _internal organs_ related symptoms (Table 3). The user gives as input information about the observed external symptoms or their values (depending on the type of the symptom). In most cases, the user may provide an image of a fish organ section. Then, the system calls the _image recognition unit_ (see Section 2.4) to automatically extract the required information. The output of this level is a list of possible diseases, ordered from the most probable to the least probable. The number of diseases may be further reduced. Figure 4: Level-Based Diagnostic Process. At the Final Level Diagnosis, if necessary, the user calls, one by one, the SESs of the diseases in the order provided in the output list.