> Do you have some examples?
Biosamples represent aspects of a thing (subject/individual/organism). These aspects can be representative for the thing as a whole (e.g. genotype from germline DNA sequencing) or a part (expression profiling of a liver biopsy). This applies obviously to non-human things.
While one can model environmental samples as belonging to an abstract thing (and e.g. metagenomic samples may have close relations to a specific plant, human … subject), they are primarily defined not in relation to a “biological thing” but to a combination of attributes (pacific ocean at geolocation… depth … time …). One _can_ have those in a common model, but there are certainly arguments against treating them the same.
(comments here informed through lengthy discussions as GA4GH Metadata Task Team co-lead etc.; not a domain modelling specialist).
Michael.