To style features with a custom function that evaluates each feature, use the context option of an OpenLayers.Style object. If the context object contains a function and this function is referenced in a symbolizer, the function will be called with the feature as an argument..
Features in the northern hemisphere are styled according to their "type" attribute. This is accomplished with a simple template that is evaluated with the feature attributes as context.
Features in the southern hemisphere are styled according to a combination of their attributes and non-attribute properties. This is accomplished using an advanced template that calls functions on the context object passed to the Style constructor.