broken

src/SIL.Machine/Corpora/CorpusAlignmentException.cs

@@ -8,5 +8,10 @@ public CorpusAlignmentException(string sourceRef, string targetRef)
             : base(
                 $"Invalid format in {sourceRef} and {targetRef}. Mismatched key formats \"{sourceRef}\" and \"{targetRef}\". There may be an extraneous tab, missing ref, or inconsistent use of user-defined refs."
             ) { }
+
+        public CorpusAlignmentException(string[] refs)
+            : base(
+                $"Invalid format in {string.Join(", ", refs)}. Mismatched key formats. There may be an extraneous tab, missing ref, or inconsistent use of user-defined refs."
+            ) { }
     }
 }

src/SIL.Machine/Corpora/INParallelTextCorpus.cs

@@ -0,0 +1,11 @@
+using System.Collections.Generic;
+
+namespace SIL.Machine.Corpora
+{
+    public interface INParallelTextCorpus : ICorpus<NParallelTextRow>
+    {
+        int Count(bool includeEmpty = true, IEnumerable<string> textIds = null);
+
+        IEnumerable<NParallelTextRow> GetRows(IEnumerable<string> textIds);
+    }
+}