"Each pixel is considered mixed, and the areal proportion of each class is estimated." (Li et al., 2014)
Li Miao, Zang Shuying, Zhang Bing, Li Shanshan and Wu Changshan. "A Review of Remote Sensing Image Classification Techniques: the Role of Spatio-contextual Information". European Journal of Remote Sensing 47, no. 1 (2014): 389-411.