image-index: define platform.os.version on Windows

Signed-off-by: Akihiro Suda <suda.akihiro@lab.ntt.co.jp>

image-index.md

@@ -55,7 +55,10 @@ For the media type(s) that this document is compatible with, see the [matrix][ma
 
     - **`os.version`** *string*
 
-        This OPTIONAL property specifies the operating system version, for example `10.0.10586`.
+        This OPTIONAL property specifies the version of the operating system targeted by the referenced blob.
+        Implementations MAY refuse to use manifests where `os.version` is not known to work with the host OS version.
+        The values are implementation-defined when `os` is `windows`. e.g. `10.0.14393.1066`.
+        The values for other `os`-es SHOULD be submitted to this specification for standardization.
 
     - **`os.features`** *array of strings*
 
@@ -114,3 +117,4 @@ For the media type(s) that this document is compatible with, see the [matrix][ma
 
 [runtime-platform2]: https://github.com/opencontainers/runtime-spec/blob/v1.0.0-rc3/config.md#platform
 [matrix]: media-types.md#compatibility-matrix
+[system-version]: https://msdn.microsoft.com/en-us/library/system.version(v=vs.110).aspx

specs-go/v1/descriptor.go

@@ -51,7 +51,7 @@ type Platform struct {
 	OS string `json:"os"`
 
 	// OSVersion is an optional field specifying the operating system
-	// version, for example `10.0.10586`.
+	// version, for example on Windows `10.0.14393.1066`.
 	OSVersion string `json:"os.version,omitempty"`
 
 	// OSFeatures is an optional field specifying an array of strings,