#381: threadFlowLocation "helper rules"

I created and merged a change draft for Yekaterina’s
Issue #381
, “Associate descriptor metadata with thread flow  locations”:

https://github.com/oasis-tcs/sarif-spec/blob/master/Documents/ChangeDrafts/Accepted/sarif-v2.0-issue-381-helper-rules.docx

Please take a look.  The entire change is pasted below.

Yekaterina and Michael : There is a subtle point that I want to discuss in a separate email. It might result in a small change to what I wrote.

Next is
Issue #387
:  “anyOf externalPropertyFileReference location or guid is required”.

Thanks,
Larry

3.37.14 taxa property
A
threadFlowLocation
MAY  contain a property named
taxa
whose value is an array of zero or more unique  (§
3.7.3
)
reportingDescriptorReference
objects  each of which specifies a category into which this
threadFlowLocation
falls.
NOTE: The motivation for this property is a tool that uses a set of rules to guide its analysis as it traces tainted data from a source to a sink. For example,  at one location, the tool might apply a rule that says: “If the input to
String.Substr
is tainted, then so is the  return value.” Such a tool can represent these “helper rules” as a custom taxonomy (§
3.19.3
),  an array of
reportingDescriptor
objects (§
3.48
). Each member  of
threadFlowLocation.taxa
can  reference one of these helper rules.
EXAMPLE: This example illustrates the scenario in the above note.
{                                # A run object (§
3.14
).
  "tool": {                      # See §
3.14.6
.
    "driver": {
      "name": "TaintDetector",
      "rules": [
        {
          "id": "TD0001",
          "name": "UntrustedDataStoredInDatabase",
          "shortDescription": {
            "text": "Data from an untrusted source was stored in a database."
          }
        },
        ...
      ],
      "taxa": [                  # Custom taxonomy (§
3.19.3
)  for helper rules.
        {                        # A reportingDescriptor object (§
3.48
).
          "id": "HR0001",
          "name": "SubstrPropogatesTaint",
          "shortDescription": {
            "text": "If the input to String.Substr is tainted,
                     so is the return value."
          }
        },
        ...
      ]
    }
  },

  "results": [                   # See §
3.14.22
.
    {                            # A result object §
3.26
.
      "ruleId": "TD0001",
      ...
      "codeFlows": [             # See §
3.26.18
.
        {                        # A codeFlow object (§
3.35
).
          "threadFlows": [       # See §
3.35.3
.
            {                    # A threadFlow object (§
3.36
).
              "locations": [     # See §
3.36.6
.
                ...
                {                # A threadFlowLocation object.
                  "location": {  # See §
3.37.3
.
                    "physicalLocation": {
                      "artifactLocation": {
                        "uri": "io/input.c",
                        "uriBaseId": "SRCROOT"
                      },
                      "region": {
                        "startLine": 32
                      }
                    }
                  },
                  "taxa": [
                    {        # A reportingDescriptorReference object (§
3.51
).
                      "id": "TD0001",
                      "index": 0
                    }
                  ]
                },
                ...
              ]
            }
          ]
        }
      ]
    }
  ]
}