[ENH] move definition of raw and derivatives datasets to common principles

[Remi-Gau]

• closes None but relates to update qMRI to align with the new definition of derivatives #1812 (comment)

---

• HTML
  • https://bids-specification--1815.org.readthedocs.build/en/1815/common-principles.html#definitions
  • note that those definitions are now also part of the glossary

---

• This makes the definition of raw and derivative both more official and easier to find.
• Add some semantic line break.

TODO

• link to the definitions in the relevant derivate related sections

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.04%. Comparing base (0950f6d) to head (e26449f).
Report is 22 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1815      +/-   ##
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+ Coverage   87.92%   88.04%   +0.11%     
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  Files          16       16              
  Lines        1375     1380       +5     
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+ Hits         1209     1215       +6     
+ Misses        166      165       -1     

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[CPernet]

ok but will you keep the intro https://bids-specification.readthedocs.io/en/stable/derivatives/introduction.html with examples or will this go away?

[Remi-Gau]

hum true that the examples look a bit weird without the previous sentence. I will put back that sentence.

[yarikoptic]

thank you! proposed some wording tune ups

[yarikoptic]

why to accent on "valid"? isn't it somewhat assumed since otherwise it is not a BIDS dataset per se?
Also we are talking about BIDS derivative dataset, right?
Also I do not see need for a conditional here.

hence I would suggest

Suggested change

	description: If a dataset is derived from at least one other valid BIDS dataset, then it is a derivative dataset.
	description: A BIDS dataset derived from at least one other BIDS dataset.

[yarikoptic]

Looking at other definitions, they are continuation of the phrase "{display_name} is ..." and hence I would adjust here too to

Suggested change

	description: A raw BIDS dataset is data that have been curated into BIDS from a non-BIDS source.
	description: A BIDS dataset that have been curated into BIDS from a non-BIDS source(s), for example data from acquisition hardware.

[effigies]

IMO, derivative and derivative dataset are not identical. If we want to define the generic term "derivative", then it should apply to files and datasets. Similarly with "raw".