The Genomic data model¶
As we have said, PyGMQL is a Python interface to the GMQL system. In order to understand how the library works, a little insights on the data model used by GMQL is necessary.
GMQL is based on a representation of the genomic information known as GDM - Genomic Data Model. Datasets are composed of samples , which in turn contains two kinds of data:
- Region values (or simply regions), aligned w.r.t. a given reference, with specific left-right ends within a chromosome. Regions can store different information regarding the “spot” they mark in a particular sample, such as region length or statistical significance. Regions of the model describe processed data, e.g. mutations, expression or bindings; they have a schema , with 5 common attributes ( id , chr , left , right , strand ) including the id of the region and the region coordinates, along the aligned reference genome, and then arbitrary typed attributes. This provides interoperability across a plethora of genomic data formats
- Metadata, storing all the knowledge about the particular sample, are arbitrary attribute-value pairs, independent from any standardization attempt; they trace the data provenance, including biological and clinical aspects
This is exemplified by the figure below, showing on the left the regions and on the right the metadata of a dataset sample.