1. An activity recognition system comprising: an activity database configured to store similarity scoring techniques for known activity graphs, each of the similarity scoring techniques being associated with activity ingestion metadata; and an activity recognition device coupled with the activity database and configured to: generate a plurality of temporal features from a digital representation of an observed activity using a feature detection algorithm; establish an observed activity graph comprising one or more clusters of temporal features generated from the digital representation, wherein each one of the one or more clusters of temporal features defines a node of the observed activity graph; select at least one contextually relevant scoring technique from the similarity scoring techniques for known activity graphs, the at least one contextually relevant scoring technique being associated with activity ingestion metadata that satisfies device context criteria defined based on device contextual attributes of the digital representation; and calculate a similarity activity score for the observed activity graph as a function of the at least one contextually relevant scoring technique, the similarity activity score being relative to at least one known activity graph.