diff --git a/specification.md b/specification.md
index c54b863..23cc09c 100644
--- a/specification.md
+++ b/specification.md
@@ -39,3 +39,20 @@ isotopes.
 - mztol is in terms of ppm.
 - mzfrac is in terms of absolute.
 - PPM = true always
+
+- First pass - (identify all of the fragments where chlorinated/brominated
+        compounds are found and carbon)
+- If isotopes exist, which ones have chlorines/bromines...
+- return a data frame.
+
+- No statistical testing required (check if it is chlorine or bromine)
+
+- Isotopes to check (Carbon, Sulfur, Chlorine, Bromine all have n+2) (check make.isos object)
+- **set all rules to false**
+
+## Isotopes
+
+- These isotopes will tend to have different intensities
+- Part of the reasoning can be attributed to differences.
+- Forseeable future, adapt to different isotopes.
+- Capture multiple outputs of different isotopes.