What is "synaptic polarity" in a chemical synapse? I'm reading a paper and they are discussing modelling the neural networks of an organism. One of the key things they are interested in is finding out the synaptic polarity of chemical synapses.  What does that term mean, and what might its relevance be?
From a paper on C.elegans:


  To understand the neural basis of these behaviors requires some information not only about the pattern and strength of the connections but also about the type of their synapses. The same neural circuit can perform different functions depending on the signs of synaptic polarities it contains. Specifically, circuits in which excitatory synapses dominate can sometimes become epileptic. On the other hand, networks with only inhibitory connections could be silent, and therefore in many situations useless. Thus, it may seem that some sort of an intermediate regime is necessary for a proper functioning of the nervous system


In that paper that's all they mean by it. It's not a very widespread term, and should not be confused with [the much more widespread term] neuronal polarity, which means the differentiation between dendrites and axon as the neuron develops. Also of note that synapses can also be classified morphologically, and when doing that there are more than two types, e.g. S-type, F-type and C-type.