Suchi Saria
Bio: I am an Assistant Professor in Computer Science in the Whiting School of Engineering and Health Policy in the Bloomberg School of Public Health at Johns Hopkins University. Prior to that, I finished my PhD in Computer Science from Stanford University with Prof. Daphne Koller as my advisor. I also spent a year as an NSF Computing Innovation Fellow visiting Harvard University collaborating with Prof. Ken Mandl and Prof. Zak Kohane.


Research: My research interests include inference and prediction in complex, heterogeneous dynamical systems, graphical models, machine learning and health systems engineering. I am particularly interested in helping solve the trillion dollar question of how can we fix our healthcare system. I develop novel ways to capture and analyze our interactions with the health care system to help make inferences about the health of an individual as well as the health system. The overarching goal is to identify opportunities and develop tools to improve the delivery of care.
On the computational front, time series data captured from passive observation of such systems present numerous challenges. The data is often high-dimensional, heterogeneous (captured from multiple measurement modalities with varying noise properties), unstructured (notion of what the right representation is often unclear) and there is often bias in what is observed. In addition, we must address challenges associated with machine learning systems that must be deployed in mission critical settings.
I'm also interested in modeling and inference challenges that arise from observational data across dynamical systems more broadly. Examples of past collaborations include modeling user activity on a desktop (the CALO project), traffic prediction from GPS data, and activity understanding from motion-sensed data.
Selected Peer-Reviewed Publications
The Digital Patient: Machine Learning Techniques for Analyzing Longitudinal Electronic Health Record data
S. Saria
PhD thesis, Stanford University, 2011
Convex envelopes of complexity controlling penalties: the case against premature envelopment
V. Jojic, S. Saria, D. Koller
In Artificial Intelligence and Statistics (AISTATS), 2011 pdf
Convex envelopes of the cardinality and rank function, l1 and nuclear norm, have gained immense popularity due to their sparsity inducing properties. This has given rise to a natural approach to building objectives with sparse optima whereby such convex penalties are added to another objective. Such a heuristic approach to objective building does not always work. For example, addition of an L1 penalty to the KL-divergence fails to induce any sparsity, as the L1 norm of any vector in a simplex is a constant. However, a convex envelope of KL and a cardinality penalty can be obtained that indeed trades off sparsity and KL-divergence. We consider the cases of two composite penalties, elastic net and fused lasso, which combine multiple desiderata. In both of these cases, we show that a hard objective relaxed to obtain penalties can be more tightly approximated. Further, by construction, it is impossible to get a better convex approximation than the ones we derive. Thus, constructing a joint envelope across different parts of the objective provides a means to trade off tightness and computational cost. [...] This work thus also implies a new way of learning sparse dynamic models.
Learning Deformable Motifs in Continuous Time Series data
S. Saria*, A. Duchi*, D. Koller
In International Joint Conference on Artificial Intelligence (IJCAI), 2011 pdf
See my thesis chapter for a longer version with a few corrections. pdf
Continuous time series data often comprise or contain repeated motifs — patterns that have similar shape, and yet exhibit nontrivial variability. Identifying these motifs, even in the presence of variation, is an important subtask in both unsupervised knowledge discovery and constructing useful features for discriminative tasks. This paper addresses this task using a probabilistic framework.
Learning individual and population level traits from Clinical Temporal data
S. Saria, D. Koller, A. Penn
In Neural Information Processing Systems (NIPS), Predictive Models in Personalized Medicine workshop, December 2010 pdf
See my thesis chapter for the detailed version with more comprehensive experiments. pdf
This paper proposes a nonparametric hierarchical Bayesian method for exploratory data analysis and feature construction in continuous time series. [...] We explore the application of modeling different continuously monitored physiological signals such as heart rate and respiratory rate from premature infants.
Combining Structured and Free-text Data for Automatic Coding of Patient Outcomes
S. Saria, G. McElvain, A. Rajani, A. Penn, D. Koller
In American Medical Informatics Association (AMIA), November 2010. pdf
Best Student Paper Finalist.
Integrating easy-to-extract structured information such as medication and treatments into current natural language processing based systems can significantly boost coding performance; in this paper, we present a system that validates this idea. [...], we develop transfer features that represent patterns that repeat across multiple complications and allow us to generalize from one label to another without having seen mentions of that feature in the training data.
Integration of Early Physiological Responses Predicts Later Illness Severity in Preterm Infants
S. Saria, A. Rajani, J. Gould, D. Koller, A. Penn
In Science Translational Medicine, September 2010. Vol. 2, Issue 48, p. 48ra65. DOI: 10.1126/scitranslmed.3001304.
Physiological data are routinely recorded in intensive care, but their use for rapid assessment of illness severity or long-term morbidity prediction has been limited. We developed a physiological assessment score for preterm newborns, akin to an electronic Apgar score, based on standard signals recorded non-invasively on admission to a neonatal intensive care unit. [...] On the computational front, a regression model (e.g., logistic regression) is frequently the approach of choice for combining heterogeneous measurements. However, a systematic way of handling different missing data assumptions, different types of data (continuous vs discrete) with different dependencies (linear vs quadratic vs non-linear) is necessary especially in the presence of sparse data where cross-validation for every choice is not practical. In this paper, we advocate a hybrid technique. Features and groups of features are modeled using simple classes of generative models inferred via maximum likelihood and combined using discriminative training.
Reasoning at the Right Time Granularity
S. Saria, U. Nodelman, D. Koller
In Uncerainty in Artificial Intelligence (UAI), July 2007. pdf
Best Student Paper
Most real-world dynamic systems are composed of different components that often evolve at very different rates. In traditional temporal graphical models, such as dynamic Bayesian networks, time is modeled at a fixed granularity, generally selected based on the rate at which the fastest component evolves. [...], we provide a new EP algorithm that utilizes a general cluster graph architecture where [...] different parts of the system can be modeled at very different time granularities, according to their current rate of evolution. We also provide an information-theoretic criterion for dynamically re-partitioning the clusters during inference to tune the level of approximation to the current rate of evolution. This avoids the need to hand-select the appropriate granularity, and allows the granularity to adapt as information is transmitted across the network. [...]
Microsoft Cambridge at TREC 13: Web and Hard Tracks
H. Zaragoza, N. Craswell, M. Taylor, S. Saria, S. Robertson
In Text Retrieval Conference (TREC), 2004. pdf
Probabilistic Plan Recognition in Multiagent Systems
S. Saria, S. Mahadevan
In Conference on Artificial Intelligence and Planning Systems (ICAPS), June 2004. pdf
We present a theoretical framework for online probabilistic plan recognition in cooperative multiagent systems. Our model extends the Abstract Hidden Markov Model (AHMM) (Bui, Venkatesh, & West 2002), and consists of a hierarchical dynamic Bayes network that allows reasoning about the interaction among multiple cooperating agents. We provide an in-depth analysis of two different policy termination schemes, T_{all} and T_{any} for concurrent action.[...] Our approximate inference procedure reduces the complexity from exponential time in N, the number of agents and K, the number of levels, to time linear in both N and K' <= K (the lowest-level of plan coordination) for the T_{all} termination scheme and O(N logN) and linear in K' for the T_{any} termination scheme.
Recent Selected Talks
November 2012
(Invited) DARPA Defense Science Office Workshop
Digital Patient Records: Need for Novel Computational Paradigms to Tackle its Complexity
November 2012
(Invited) AAAI Fall Symposium on Information Retrieval and Knowledge Discovery in Biomedical Text
Learning from Electronic Medical Record data
October 2012
(Invited) NSF/NIH/CCC Computing and Health symposium, Exploiting Data in Abundance panel (link)
Computational challenges in working with Health data
September 2012
Center for Health Services and Outcomes Research, Bloomberg School of Public Health, Johns Hopkins University (link)
Machine Learning for Quality Improvement in the nICU: Early risk prediction from device and EHR data
September 2012
(Invited) Non-parametric Bayes symposium at Institute of Computational and Experimental Research in Mathematics (ICERM), Providence RI (link)
Discovery and Prediction from Clinical Temporal Data
June 2012
(Invited) International Society for Bayesian Analysis, Kyoto, Japan (link)
Predicing infants at risk: Non-parametric Bayes to the rescue!
May 2012
(Invited) Yahoo! Machine Learning Seminar, University of Maryland, College Park
Modeling Individual and Population traits from Clinical Temporal Data
April 2012
(Invited) University of Washington, St. Louis, Computer Science Seminar
Discovery and Prediction from Clinical Temporal Data
April 2012
(Invited) Grand Rounds, School of Biomedical Informatics, Vanderbilt University
Secondary use of EHR data through machine learning: Real-time Risk Prediction in the Neonatal ICU
December 2011
(Invited) Indo-US workshop on Large Scale Data Analytics and Intelligent Services, Indian Institute of Science, Bangalore, India
Methods for discovery from ICU data
November 2011
(Invited) Meaching Learning in Health Care, INFORMS (The annual Operations Research meeting), Charlotte, NC (link)
Discovering Shared and Individual Traits from Clinical Temporal Data

Older talks with slides:
July 2011
(Selected) International Joint Conference of Artificial Intelligence (IJCAI)(link)
Discovering Deformable Shape Motifs from Continuous Time Series Data
November 2010
(Selected) American Medical Informatics Association, Washington D.C.
Combining Structured and Free-Text Data for Automatic Coding of Patient Outcomes pdf
July 2007
Uncertainty in AI, Vancouver B.C.
(Selected) Reasoning at the Right Time Granularity pdf
Press

Some popular press sources where my thesis work has appeared:
, , , , breaking news section, , and some that I cannot read.
Recent Events
2012/10/11 — At the NSF/NIH/CCC meeting for future directions in Healhcare and Computing. Panel talk on computational challenges for computing on health systems data.
2012/09/24 — Featured by NSF in their Bits and Bytes Publication and here is a copy of their write-up.
2012/08/12 — Finished co-organizing the Meaningful Use of Complex Medical Data symposium. Turned out to a great meeting! Summary of the symposium.
2012/08/01 — Moving from Harvard to Hopkins in a week. The NSF Computing Innovation Fellowship was a great opportunity. Really looking forward to Hopkins!
Contact
Hackerman Hall 227
Department of Computer Science,
Johns Hopkins University,
3400 N. Charles St,
Baltimore, MD 21218
ssaria AT cs DOT jhu DOT edu

Hampton House 502,
Department of Health Policy & Management,
Bloomberg School of Public Health,
624 N. Broadway,
Baltimore, MD 21205
ssaria AT jhsph DOT edu