13. The method of claim 10 , further comprising: determining an average cluster purity score for the set of clusters, the average cluster purity score indicating an average percentage of containers in the set of clusters that are associated with the semantic classifier; determining a maximum page coverage value associated with a particular cluster of the set of clusters, the maximum page coverage value indicating that the particular cluster includes a minimum number of containers not associated with the semantic classifier among the set of clusters; assigning a first weight to the average cluster purity score to obtain a weighted average cluster purity score, the first weight being associated with a particular candidate content property; assigning a second weight to the maximum page coverage value to obtain a weighted maximum page coverage value, the second weight being associated with the particular candidate content property; determining a combined weighted value from the weighted average cluster purity score and the weighted maximum page coverage value; determining that the combined weighted value meets a threshold value; and selecting the particular candidate content property for inclusion in the second set of one or more content properties.
10. The method of claim 5 , further comprising: receiving a test dataset comprising test container data corresponding to multiple containers of test digital content; selecting a set of one or more candidate content properties; selecting a candidate distance function; executing, using the candidate distance function and the set of one or more candidate content properties, a first iteration of the clustering algorithm on the test container data to obtain a set of clusters associated with the test digital content, each cluster in the set of clusters comprising a respective one or more of the multiple containers of the test digital content; and determining a cluster purity score of a first cluster in the set of clusters, the first cluster purity score indicating a percentage of containers in the first cluster that are associated with a semantic classifier.