Refinement of MCAP Specification

Signed-off-by: Timm Ruppert <timm.ruppert@persival.de>

Author: TimmRuppert

doc/architecture/trace_file_mcap_format.adoc

@@ -4,6 +4,7 @@
 - Must comply with the https://mcap.dev/spec[MCAP format specification] version `0x30`
 - Must allow other non-OSI data to be present in the MCAP file
 - Message records must be written into `chunk records` for indexed files
+- Only OSI top-level messages containing a timestamp field are permitted to be directly stored in MCAP channels
 
 == Schema
 - `name` field: Full message type name, including package (e.g., `osi3.SensorData`)
@@ -12,12 +13,13 @@
 
 == Channel
 - `message_encoding` field: Must be "protobuf"
-- `metadata` field: Should include a brief description of data origin and purpose
+- `metadata` field:
+  - Must include an `osi_version` key, specifying the OSI SemVer version of the message contained within the channel
+  - Should include a `description` key explaining the data's origin and purpose
 
 == Message
 - `publish_time` field: 
   - Must reflect the timestamp of the stored OSI top-level message if it contains a timestamp field
-  - Should represent a plausible value to express message order in relation to timestamps of other top-level messages if the message doesn't contain a timestamp (e.g. SensorViewConfiguration)
   - Must be in nanoseconds
 - `log_time` field: Must reflect the time when the message was enqueued for MCAP file addition
   - Must reflect the time when the top-level OSI message was enqueued for addition to the MCAP file
@@ -26,7 +28,7 @@
 
 == Metadata
 - Must include metadata with the name `versions` containing at least the following key-value pairs:
-  * `osi`: SemVer version of OSI specification
+  * `osi`: SemVer version of the minimum required OSI version
   * `protobuf`: SemVer version of protobuf library
 - Must include metadata with the name `creation_date` containing at least the following key-value pairs:
   * `timestamp`: ISO 8601 formatted creation time
@@ -35,5 +37,4 @@
 - Additional custom metadata may be added
 
 == Compression
-- OSI-compliant tooling must support compression types: `none`, `lz4`, and `zstd`
-- Recommended compression in use should be either `lz4` or `zstd`
+- OSI-compliant tooling must support compression types: `none`, `lz4`, and `zstd`