enh: add compressed TSV files to the common principles

Their description is hedged within the physiological recordings so
upcasting them to the common principles seems important.

src/common-principles.md

@@ -542,6 +542,32 @@ like in the example below.
 }
 ```
 
+### Compressed tabular files
+
+Large tabular information such as physiological recordings MAY be stored with
+[compressed tab-delineated (TSVGZ) files](glossary.md#tsvgz-extensions).
+Rules for formatting plain-text tabular files apply to TSVGZ files with three exceptions:
+
+1.  The contents of TSVGZ files SHOULD be compressed with
+    [gzip](https://datatracker.ietf.org/doc/html/rfc1952).
+1.  Compressed tabular files SHOULD NOT contain a header in the first row
+    indicating the column names.
+1.  TSVGZ files SHOULD be accompanied by a JSON file with the same name as their
+    corresponding tabular file but with a `.json` extension.
+
+???+ warning "Columns of TSVGZ files MUST be defined in the corresponding JSON sidecar and the tabular content MUST NOT include a header line."
+
+    In contrast to plain-text TSV files, compressed tabular files files
+    MUST NOT include a header line.
+    Column names MUST be specified in the JSON file following the
+    [`Columns` metadata](glossary.md#columns-metadata) specifications.
+    As plain-text tabular data, column names MUST NOT be blank (that is, an empty string),
+    and MUST NOT be duplicated within a single JSON file describing a TSVGZ file.
+
+    TSVGZ are header-less to improve compatibility with existing software
+    (for example, FSL, or PNM), and to facilitate the support for other file formats
+    in the future.
+
 ### Key-value files (dictionaries)
 
 JavaScript Object Notation (JSON) files MUST be used for storing key-value

src/modality-specific-files/physiological-and-other-continuous-recordings.md

@@ -2,12 +2,9 @@
 
 Physiological recordings such as cardiac and respiratory signals and other
 continuous measures (such as parameters of a film or audio stimuli) MAY be
-specified using two files:
-
-1.  a [gzip](https://datatracker.ietf.org/doc/html/rfc1952)
-    compressed TSV file with data (without header line)
-
-1.  a JSON file for storing metadata fields (see below)
+specified using a [compressed tabular file](../common-principles.md#compressed-tabular-files)
+([TSVGZ file](../glossary.md#tsvgz-extensions)) and a corresponding
+JSON file for storing metadata fields (see below).
 
 !!! example "Example datasets"
 
@@ -38,8 +35,10 @@ before the suffix.
 For example for the file `sub-control01_task-nback_run-1_bold.nii.gz`,
 `<matches>` would correspond to `sub-control01_task-nback_run-1`.
 
-Note that when supplying a `*_<physio|stim>.tsv.gz` file, an accompanying
-`*_<physio|stim>.json` MUST be supplied as well.
+!!! warning "TSVGZ files SHOULD NOT include a header line (as established by the [common-principles](../common-principles.md#compressed-tabular-files))"
+
+    As a result, when supplying a `*_<physio|stim>.tsv.gz` file, an accompanying
+    `*_<physio|stim>.json` MUST be supplied as well.
 
 The [`recording-<label>`](../appendices/entities.md#recording)
 entity MAY be used to distinguish between several recording files.
@@ -66,15 +65,6 @@ A guide for using macros can be found at
 Additional metadata may be included as in
 [any TSV file](../common-principles.md#tabular-files) to specify, for
 example, the units of the recorded time series.
-Please note that, in contrast to other TSV files in BIDS, the TSV files specified
-for physiological and other continuous recordings *do not* include a header
-line.
-Instead the name of columns are specified in the JSON file (see `Columns` field).
-This is to improve compatibility with existing software (for example, FSL, PNM)
-as well as to make support for other file formats possible in the future.
-As in any TSV file, column names MUST NOT be blank (that is, an empty string),
-and MUST NOT be duplicated within a single JSON file describing a headerless
-TSV file.
 
 Example `*_physio.tsv.gz`: