raw values type

Added text to the Raw Values Type section. Fixes issue #9

draft-ietf-rats-corim.md

@@ -991,7 +991,19 @@ computing base.
 
 ###### Raw Values Types {#sec-comid-raw-value-types}
 
-[^issue] https://github.com/ietf-rats-wg/draft-ietf-rats-corim/issues/9
+Raw value measurements are typically vendor defined values that are checked by Verifiers
+for consistency only, since the security relevance is opaque to Verifiers.
+
+There are two parts to a `raw-value-group`, a measurement and an optional mask.
+The default raw value measurement is a CBOR tagged `bstr`.
+Additional raw value types can be defined, but must be CBOR tagged so that parsers can distinguish
+between the various forms.
+
+The mask is applied by the Verifier as part of appraisal.
+Only the raw value bits with corresponding TRUE mask bits are compared during appraisal.
+
+When a new raw value type is defined, the convention for applying the mask is also defined.
+Typically, a CoRIM profile is used to define new raw values and mask semantics.
 
 ~~~ cddl
 {::include cddl/raw-value.cddl}