title: Hierarchical Span-Based Conditional Random Fields for Labeling and Segmenting Events in Wearable Sensor Data Streams.
abstract: The field of mobile health (mHealth) has the potential to yield new insights into health and behavior through the analysis of continuously recorded data from wearable health and activity sensors. In this paper, we present a hierarchical span-based conditional random field model for the key problem of jointly detecting discrete events in such sensor data streams and segmenting these events into high-level activity sessions. Our model includes higher-order cardinality factors and inter-event duration factors to capture domain-specific structure in the label space. We show that our model supports exact MAP inference in quadratic time via dynamic programming, which we leverage to perform learning in the structured support vector machine framework. We apply the model to the problems of smoking and eating detection using four real data sets. Our results show statistically significant improvements in segmentation performance relative to a hierarchical pairwise CRF.
authors.affiliation: University of Massachusetts Amherst, 140 Governors Drv, Amherst, MA 01003, RJADAMS@CS.UMASS.EDU.
authors.forename: Roy J
authors.initials: RJ
authors.lastname: Adams
authors.affiliation: University of Memphis, 375 Dunn Hall, Memphis, TN 38152, NSLEHEEN@MEMPHIS.EDU.
authors.forename: Nazir
authors.initials: N
authors.lastname: Saleheen
authors.affiliation: The University of Texas at Austin, 110 Inner Campus Drive, Austin, TX 78705, ETHOMAZ@UTEXAS.EDU.
authors.forename: Edison
authors.initials: E
authors.lastname: Thomaz
authors.affiliation: Lumme Inc, 34 Main St, Amherst, MA 01002, APARATE@CS.UMASS.EDU.
authors.forename: Abhinav
authors.initials: A
authors.lastname: Parate
authors.affiliation: University of Memphis, 375 Dunn Hall, Memphis, TN 38152, SKUMAR4@MEMPHIS.EDU.
authors.forename: Santosh
authors.initials: S
authors.lastname: Kumar
authors.affiliation: University of Massachusetts Amherst, 140 Governors Drv, Amherst, MA 01003, MARLIN@CS.UMASS.EDU.
authors.forename: Benjamin M
authors.initials: BM
authors.lastname: Marlin