Proposal: measurementLists Group as alternative to many measurementList1...measurementList2 indexed groups

.github/workflows/wordlist.txt

@@ -281,3 +281,4 @@ dataOffset
 forihuelaespina
 StO
 StO2
+measurementLists

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 SNIRF uses the [Semantic Versioning](https://semver.org) scheme.
 
+### `2.0` In development
+* Add `nirs(i)/data(j)/measurementLists` as an alternative to the indexed-Group measurementList `nirs(i)/data(j)/measurementList(k)`.
 
 ### `v1.1`
 
@@ -22,7 +24,7 @@ SNIRF uses the [Semantic Versioning](https://semver.org) scheme.
 * Added language preventing `metaDataTags` sub-groups
 * Added notice that the summary table is intended to be machine-readable
 * Removed local channel indexing owing to incomplete specification.
-  
+
 ### `v1.0` (September 23 2021)
 
 [View this version of the specification](https://github.com/fNIRS/snirf/blob/v1.0/snirf_specification.md)  

snirf_specification.md

@@ -411,7 +411,7 @@ a time spacing of 0.2 (s) indicates a sampling rate of 5 Hz.
 Chunked data is allowed to support real-time streaming of data in this array.
 
 #### /nirs(i)/data(j)/measurementList(k) 
-* **Presence**: required
+* **Presence**: required if `measurementLists` is not present
 * **Type**:  indexed group
 * **Location**: `/nirs(i)/data(j)/measurementList(k)`
 
@@ -537,6 +537,119 @@ As described below, optional variables `probe.sourceLabels` and
 `probe.detectorLabels` are provided for indicating the instrument specific 
 label for sources and detectors.
 
+#### /nirs(i)/data(j)/measurementLists
+* **Presence**: optional
+* **Type**:  group
+* **Location**: `/nirs(i)/data(j)/measurementLists`
+
+The group for measurement list variables which map the data array onto the probe geometry (sources and detectors), data type, and wavelength. This group's datasets are arrays with size `<number of channels>`, with each position describing the corresponding column in the data matrix. (i.e. the values at `measurementLists/sourceIndex(3)` and `measurementLists/detectorIndex(3)` correspond to `dataTimeSeries(:,3)`).
+
+This group is required only if the indexed-group format `/nirs(i)/data(j)/measurementList(k)` is not used to encode the measurement list. `measurementLists` is an alternative that may offer better performance for larger probes.
+
+The arrays of `measurementLists` are:
+
+#### /nirs(i)/data(j)/measurementLists/sourceIndex 
+* **Presence**: required if measurementLists is present
+* **Type**:  integer 1-D array
+* **Location**: `/nirs(i)/data(j)/measurementLists/sourceIndex`
+
+Must be 1-D array with length equal to the size of the second dimension of `/nirs(i)/data(j)/dataTimeSeries`. Source indices for each channel.
+
+#### /nirs(i)/data(j)/measurementLists/detectorIndex 
+* **Presence**: required if measurementLists is present
+* **Type**:  integer 1-D array
+* **Location**: `/nirs(i)/data(j)/measurementLists/detectorIndex`
+
+Must be 1-D array with length equal to the size of the second dimension of `/nirs(i)/data(j)/dataTimeSeries`. Detector indices for each channel.
+
+#### /nirs(i)/data(j)/measurementLists/wavelengthIndex 
+* **Presence**: required if measurementLists is present
+* **Type**:  integer 1-D array
+* **Location**: `/nirs(i)/data(j)/measurementLists/wavelengthIndex`
+
+Must be 1-D array with length equal to the size of the second dimension of `/nirs(i)/data(j)/dataTimeSeries`. Index of the "nominal" wavelength (in `probe.wavelengths`) per channel.
+
+#### /nirs(i)/data(j)/measurementLists/wavelengthActual 
+* **Presence**: optional
+* **Type**:  numeric 1-D array
+* **Location**: `/nirs(i)/data(j)/measurementLists/wavelengthActual`
+
+Must be 1-D array with length equal to the size of the second dimension of `/nirs(i)/data(j)/dataTimeSeries`. Actual (measured) wavelength in nm, if available, for the source in each channel.
+
+#### /nirs(i)/data(j)/measurementLists/wavelengthEmissionActual
+* **Presence**: optional
+* **Type**:  numeric 1-D array
+* **Location**: `/nirs(i)/data(j)/measurementLists/wavelengthEmissionActual`
+
+Must be 1-D array with length equal to the size of the second dimension of `/nirs(i)/data(j)/dataTimeSeries`. Actual (measured) emission wavelength in nm, if available, for the source in each channel.
+
+#### /nirs(i)/data(j)/measurementLists/dataType 
+* **Presence**: required if measurementLists is present
+* **Type**:  integer 1-D array
+* **Location**: `/nirs(i)/data(j)/measurementLists/dataType`
+
+Must be 1-D array with length equal to the size of the second dimension of `/nirs(i)/data(j)/dataTimeSeries`. See Appendix for list of possible values.
+
+#### /nirs(i)/data(j)/measurementLists/dataUnit 
+* **Presence**: optional
+* **Type**:  string 1-D array
+* **Location**: `/nirs(i)/data(j)/measurementLists/dataUnit`
+
+Must be 1-D array with length equal to the size of the second dimension of `/nirs(i)/data(j)/dataTimeSeries`. International System of Units (SI units) identifier for each channel.
+
+#### /nirs(i)/data(j)/measurementLists/dataTypeLabel 
+* **Presence**: optional
+* **Type**:  string 1-D array
+* **Location**: `/nirs(i)/data(j)/measurementLists/dataTypeLabel`
+
+Data-type label. Must be 1-D array with length equal to the size of the second dimension of `/nirs(i)/data(j)/dataTimeSeries`.
+
+#### /nirs(i)/data(j)/measurementLists/dataTypeIndex 
+* **Presence**: required if measurementLists is present
+* **Type**:  integer 1-D array
+* **Location**: `/nirs(i)/data(j)/measurementLists/dataTypeIndex`
+
+Data-type specific parameter indices. Must be 1-D array with length equal to the size of the second dimension of `/nirs(i)/data(j)/dataTimeSeries`. Note that the Time Domain and Diffuse Correlation Spectroscopy data types have two additional parameters and so `dataTimeIndex` must be a 2-D array with 2 columns that index the additional parameters.
+
+#### /nirs(i)/data(j)/measurementLists/sourcePower 
+* **Presence**: optional
+* **Type**:  numeric 1-D array
+* **Location**: `/nirs(i)/data(j)/measurementLists/sourcePower`
+
+Must be 1-D array with length equal to the size of the second dimension of `/nirs(i)/data(j)/dataTimeSeries`. Units are optionally defined in `metaDataTags`.
+
+#### /nirs(i)/data(j)/measurementLists/detectorGain 
+* **Presence**: optional
+* **Type**:  numeric 1-D array
+* **Location**: `/nirs(i)/data(j)/measurementLists/detectorGain`
+
+Must be 1-D array with length equal to the size of the second dimension of `/nirs(i)/data(j)/dataTimeSeries`. Units are optionally defined in `metaDataTags`.
+
+#### /nirs(i)/data(j)/measurementLists/moduleIndex 
+* **Presence**: optional
+* **Type**:  integer 1-D array
+* **Location**: `/nirs(i)/data(j)/measurementLists/moduleIndex`
+
+Index of a repeating module. Must be 1-D array with length equal to the size of the second dimension of `/nirs(i)/data(j)/dataTimeSeries`.
+
+#### /nirs(i)/data(j)/measurementLists/sourceModuleIndex 
+* **Presence**: optional
+* **Type**:  integer 1-D array
+* **Location**: `/nirs(i)/data(j)/measurementLists/sourceModuleIndex`
+
+Index of the module that contains the source of the channel. 
+This index must be used together with `detectorModuleIndex`, and 
+can not be used when `moduleIndex` presents. Must be 1-D array with length equal to the size of the second dimension of `/nirs(i)/data(j)/dataTimeSeries`.
+
+#### /nirs(i)/data(j)/measurementLists/detectorModuleIndex 
+* **Presence**: optional
+* **Type**:  integer 1-D array
+* **Location**: `/nirs(i)/data(j)/measurementLists/detectorModuleIndex`
+
+Index of the module that contains the detector of the channel. 
+This index must be used together with `sourceModuleIndex`, and 
+can not be used when `moduleIndex` presents. Must be 1-D array with length equal to the size of the second dimension of `/nirs(i)/data(j)/dataTimeSeries`.
+
 #### /nirs(i)/stim(j) 
 * **Presence**: optional
 * **Type**:  indexed group
@@ -574,7 +687,7 @@ used to annotate the meanings of each data column.
 
 #### /nirs(i)/stim(j)/dataLabels
 * **Presence**: optional 
-* **Type**:  string array
+* **Type**:  string 1-D array
 * **Location**: `/nirs(i)/stim(j)/dataLabels(k)`
 
 This is a string array providing annotations for each data column in 
@@ -754,7 +867,7 @@ wavelengths>`. This is indexed by `measurementList(k).sourceIndex` and
 
 #### /nirs(i)/probe/detectorLabels 
 * **Presence**: optional 
-* **Type**:  string array
+* **Type**:  string 1-D array
 * **Location**: `/nirs(i)/probe/detectorLabels(j)`
 
 This is a string array providing user friendly or instrument specific labels 
@@ -793,7 +906,7 @@ index to the labels of the given landmark. Label names are stored in the
 
 #### /nirs(i)/probe/landmarkLabels(j) 
 * **Presence**: optional 
-* **Type**:  string array
+* **Type**:  string 1-D array
 * **Location**: `/nirs(i)/probe/landmarkLabels(j)`
 
 This string array stores the names of the landmarks. The first string denotes