2 files changed, 27 insertions, 3 deletions
diff --git a/src/sisudoc/ocda/abstraction/ssp.d b/src/sisudoc/ocda/abstraction/ssp.d
index 6aa55c2..3e80956 100644
--- a/src/sisudoc/ocda/abstraction/ssp.d
+++ b/src/sisudoc/ocda/abstraction/ssp.d
@@ -414,7 +414,11 @@ template spineAbstractionTxt() {
   import std.string;
   import std.array;
   mixin sspObjectRecord;
-  void spineAbstractionTxt(D)(D doc) {
+  /+ ↓ the whole .ssp for a document, as lines. the file writer below emits
+       these, and the abstraction db is built by reading them back, so the
+       database cannot carry anything the .ssp does not
+  +/
+  string[] sspDocumentLines(D)(D doc) {
     auto doc_abstraction = doc.abstraction;
     auto doc_matters     = doc.matters;
     string[] output;
@@ -556,6 +560,11 @@ template spineAbstractionTxt() {
       output ~= "}";
       output ~= "";
     }
+    return output;
+  }
+  void spineAbstractionTxt(D)(D doc) {
+    auto doc_matters = doc.matters;
+    string[] output = sspDocumentLines(doc);
     /+ ↓ write to file +/
     /+ path: <output_path>/<language>/abstraction/<doc_uid_out>.ssp +/
     string out_root = (doc_matters.output_path.length > 0)
diff --git a/src/sisudoc/ocda/abstraction/ssp_in.d b/src/sisudoc/ocda/abstraction/ssp_in.d
index f0fb963..220bfe3 100644
--- a/src/sisudoc/ocda/abstraction/ssp_in.d
+++ b/src/sisudoc/ocda/abstraction/ssp_in.d
@@ -198,11 +198,16 @@ template spineAbstractionRead() {
             obj.metainfo.identifier         = _tail[_sp + 1 .. $];
           } else {
             obj.metainfo.heading_lev_markup = _levOfMarkedUp(_tail);
-            obj.metainfo.identifier         = obj.metainfo.ocn.to!string;
+            /+ ↓ omitted means it equals the ocn, and for an object with no ocn
+                 it was empty: "a"~N identifiers are always written
+            +/
+            obj.metainfo.identifier         = (obj.metainfo.ocn != 0)
+              ? obj.metainfo.ocn.to!string : "";
           }
         } else {
           obj.metainfo.is_a     = _rest;
-          obj.metainfo.identifier = obj.metainfo.ocn.to!string;
+          obj.metainfo.identifier = (obj.metainfo.ocn != 0)
+            ? obj.metainfo.ocn.to!string : "";
         }
         obj.metainfo.is_of_section = section;
         continue;
@@ -327,6 +332,16 @@ template spineAbstractionRead() {
     }
     return doc;
   }
+  /+ ↓ the abstraction as it survives a trip through the .ssp text: emitted
+       as lines by the writer, read straight back. what a consumer built
+       from this cannot see, the .ssp does not carry, which is what makes a
+       second artefact built from it unable to drift
+  +/
+  auto sspRoundTripAbstraction(D)(D doc) {
+    import sisudoc.ocda.abstraction.ssp;
+    mixin spineAbstractionTxt;
+    return sspRead(sspDocumentLines(doc)).abstraction;
+  }
   SSPdocument sspReadFile(string file_path) {
     string[] _lines;
     try {