4 files changed, 41 insertions, 8 deletions

diff --git a/org/in_source_files.org b/org/in_source_files.org
index 0f50150..0a87ec4 100644
--- a/org/in_source_files.org
+++ b/org/in_source_files.org
@@ -930,11 +930,16 @@ 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;
@@ -1059,6 +1064,16 @@ 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 {
diff --git a/org/out_src_abstraction_ocda_peg_ssp.org b/org/out_src_abstraction_ocda_peg_ssp.org
index 3be6ce2..a541513 100644
--- a/org/out_src_abstraction_ocda_peg_ssp.org
+++ b/org/out_src_abstraction_ocda_peg_ssp.org
@@ -396,7 +396,11 @@ 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;
@@ -538,6 +542,11 @@ 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/org/out_src_abstraction_sqlite_db.org b/org/out_src_abstraction_sqlite_db.org
index 3daf045..6159fdd 100644
--- a/org/out_src_abstraction_sqlite_db.org
+++ b/org/out_src_abstraction_sqlite_db.org
@@ -42,9 +42,12 @@ template spineAbstractionDb() {
   import std.array;
   import d2sqlite3;
   import sisudoc.outputs.io_out.paths_output;
-
-  void spineAbstractionDb(D)(D doc) {
-    auto doc_abstraction = doc.abstraction;
+  /+ ↓ the abstraction is passed in rather than taken from doc, because the
+       caller hands over one that has been through the .ssp: written as text
+       and read back. so the database is a function of the .ssp and cannot
+       carry anything the .ssp does not
+  +/
+  void spineAbstractionDb(D,A)(D doc, A doc_abstraction) {
     auto doc_matters     = doc.matters;
 
     /+ ↓ determine output path +/
diff --git a/org/spine.org b/org/spine.org
index 722f235..84e4d04 100644
--- a/org/spine.org
+++ b/org/spine.org
@@ -1719,10 +1719,16 @@ if (doc.matters.opt.action.show_abstraction) {
 
 #+NAME: spine_each_file_show_abstraction_db
 #+BEGIN_SRC d
-/+ ↓ document abstraction sqlite database +/
+/+ ↓ document abstraction sqlite database, built from the .ssp: the
+     lines are emitted and read straight back, and the objects that
+     come out are what is written, so the database cannot carry
+     anything the .ssp does not
++/
 if (doc.matters.opt.action.show_abstraction_db) {
+  import sisudoc.ocda.abstraction.ssp_in;
   import sisudoc.outputs.io_out.create_abstraction_db;
-  spineAbstractionDb!()(doc);
+  mixin spineAbstractionRead;
+  spineAbstractionDb!()(doc, sspRoundTripAbstraction(doc));
 }
 #+END_SRC