Interacting with data through ADAM’s evidence access layer¶
ADAM exposes access to distributed datasets of genomic data through the ADAMContext entrypoint. The ADAMContext wraps Apache Spark’s SparkContext, which tracks the configuration and state of the current running Spark application. On top of the SparkContext, the ADAMContext provides data loading functions which yield GenomicDatasets. The GenomicDataset classes provide a wrapper around Apache Spark’s two APIs for manipulating distributed datasets: the legacy Resilient Distributed Dataset (Zaharia et al. 2012) and the new Spark SQL Dataset/DataFrame API (Armbrust et al. 2015). Additionally, the GenomicDataset is enriched with genomics-specific metadata such as computational lineage and sample metadata, and optimized genomics-specific query patterns such as region joins and the auto-parallelizing pipe API for running legacy tools using Apache Spark.
All GenomicDatasets include a sequence dictionary which describes the reference genome that the data in the genomic dataset are aligned to, if one is known. Additionally, RecordGroupGenomicDataset store a dictionary with read groups that are attached to the reads/fragments. Similarly, the MultisampleGenomicDataset includes a list of samples who are present in the dataset.