Filter weak Crossref discovered references

README.md

@@ -159,6 +159,8 @@ Broad BibTeX exports skip DOI-only placeholder records such as `Referenced work
 
 Long-running CLI commands report progress on `stderr` so `stdout` remains clean for JSON, BibTeX, or tabular output.
 
+Crossref reference expansion is intentionally conservative about weak discoveries. If a cited reference has no DOI and Crossref only exposes it as an unstructured citation blob, `expand --source crossref`, `expand-topic --source crossref`, and bootstrap flows now skip materializing that record unless the fallback metadata looks like a cleaner non-`misc` work such as conference proceedings. This reduces junk `@misc` entries whose `title` field is really a pasted citation string.
+
 For live-source development, prefer fixture-backed or cache-backed source clients so resolver and expansion work can be exercised repeatedly without re-hitting upstream APIs on every run.
 
 ## Example Application

examples/cli/README.md

@@ -211,6 +211,8 @@ Re-enrich all current `@misc` entries with DOIs:
 .venv/bin/python -m citegeist --db library.sqlite3 resolve-stubs --doi-only --all-misc --limit 25
 ```
 
+When Crossref expansion only yields an unstructured citation blob without a DOI, citegeist now skips materializing that discovery instead of storing it as a weak `@misc` entry. Cleaner fallback cases that infer a more specific type, such as proceedings-like titles, are still admitted.
+
 ## Explore Citation Graphs
 
 Purpose: traverse citation edges, export graph data, and render quick visualizations.

src/citegeist/expand.py

@@ -58,6 +58,8 @@ class CrossrefExpander:
         results: list[ExpansionResult] = []
         for index, reference in enumerate(references, start=1):
             discovered = self._reference_to_entry(reference, citation_key, index)
+            if discovered is None:
+                continue
             created = False
             if store.get_entry(discovered.citation_key) is None:
                 store.upsert_entry(
@@ -89,17 +91,22 @@ class CrossrefExpander:
             )
         return results
 
-    def _reference_to_entry(self, reference: dict, source_citation_key: str, ordinal: int) -> BibEntry:
+    def _reference_to_entry(
+        self,
+        reference: dict,
+        source_citation_key: str,
+        ordinal: int,
+    ) -> BibEntry | None:
         fallback = _crossref_reference_to_entry(reference, source_citation_key, ordinal)
         doi = reference.get("DOI") or ""
         if not doi:
-            return fallback
+            return None if _skip_crossref_reference(reference, fallback) else fallback
 
         resolution = self.resolver.resolve_doi(doi)
         if resolution is None:
             resolution = self.resolver.resolve_datacite_doi(doi)
         if resolution is None:
-            return fallback
+            return None if _skip_crossref_reference(reference, fallback) else fallback
 
         merged = merge_entries(resolution.entry, fallback)
         merged.fields["note"] = fallback.fields["note"]
@@ -341,6 +348,8 @@ class TopicExpander:
         rows: list[tuple[ExpansionResult, dict[str, object]]] = []
         for index, reference in enumerate(references, start=1):
             discovered = self.crossref_expander._reference_to_entry(reference, citation_key, index)
+            if discovered is None:
+                continue
             rows.append(
                 (
                     ExpansionResult(
@@ -425,6 +434,44 @@ def _crossref_reference_to_entry(reference: dict, source_citation_key: str, ordi
     return BibEntry(entry_type=entry_type, citation_key=citation_key, fields=fields)
 
 
+def _skip_crossref_reference(reference: dict, entry: BibEntry) -> bool:
+    if reference.get("DOI"):
+        return False
+    if reference.get("article-title") or reference.get("volume-title"):
+        return False
+
+    title = str(entry.fields.get("title") or "")
+    normalized_title = _normalize_text(title)
+    if not normalized_title:
+        return True
+    if normalized_title.casefold().startswith("referenced work "):
+        return True
+    if normalized_title[0] in ".,;:)":
+        return True
+
+    unstructured = _normalize_text(str(reference.get("unstructured") or ""))
+    if not unstructured:
+        return not bool(reference.get("journal-title"))
+    if entry.entry_type == "misc":
+        return True
+    return _looks_like_citation_blob(unstructured)
+
+
+def _looks_like_citation_blob(text: str) -> bool:
+    lowered = text.casefold()
+    if any(token in lowered for token in ("http://", "https://", "www.", " accessed ", " url ")):
+        return True
+    if any(token in lowered for token in ("supporting material", "grant", "poll results", "prescribing information")):
+        return True
+    if text.count(",") >= 3 or text.count(";") >= 2:
+        return True
+    if re.search(r"\(\d{4}\)", text):
+        return True
+    if re.search(r"\b[A-Z]\.[ ]?[A-Z]?\.", text):
+        return True
+    return False
+
+
 def _reference_citation_key(reference: dict, title: str, year: str, ordinal: int) -> str:
     if doi := reference.get("DOI"):
         suffix = re.sub(r"[^A-Za-z0-9]+", "", doi).lower()

tests/test_expand.py

@@ -59,14 +59,11 @@ def test_crossref_expander_creates_draft_nodes_and_relations():
 
         results = expander.expand_entry_references(store, "seed2024")
 
-        assert [result.discovered_citation_key for result in results] == [
+        assert [result.discovered_citation_key for result in results] == ["doi101000exampleref"]
-            "doi101000exampleref",
-            "ref2021unstructured2",
-        ]
         discovered = store.get_entry("doi101000exampleref")
         assert discovered is not None
         assert discovered["review_status"] == "draft"
-        assert store.get_relations("seed2024") == ["doi101000exampleref", "ref2021unstructured2"]
+        assert store.get_relations("seed2024") == ["doi101000exampleref"]
         relation_provenance = store.get_relation_provenance("seed2024")
         assert relation_provenance[0]["source_type"] == "graph_expand"
     finally:
@@ -142,6 +139,78 @@ def test_crossref_reference_to_entry_infers_non_misc_for_proceedings_like_text()
     assert entry.entry_type == "inproceedings"
 
 
+def test_crossref_expander_skips_citation_blob_without_identifier():
+    store = BibliographyStore()
+    try:
+        store.ingest_bibtex(
+            """
+@article{seed2024,
+  author = {Seed, Alice},
+  title = {Seed Paper},
+  year = {2024},
+  doi = {10.1000/seed-doi}
+}
+"""
+        )
+
+        expander = CrossrefExpander()
+        expander.resolver.source_client.get_json = lambda _url: {  # type: ignore[method-assign]
+            "message": {
+                "reference": [
+                    {
+                        "unstructured": (
+                            "Abraham, J.K., Meir, E., Perry, J. (2009). "
+                            "Addressing undergraduate student misconceptions. "
+                            "https://example.org/article"
+                        ),
+                        "year": "2009",
+                    }
+                ]
+            }
+        }
+
+        assert expander.expand_entry_references(store, "seed2024") == []
+        assert store.get_relations("seed2024") == []
+    finally:
+        store.close()
+
+
+def test_crossref_expander_keeps_simple_unstructured_title_without_identifier():
+    store = BibliographyStore()
+    try:
+        store.ingest_bibtex(
+            """
+@article{seed2024,
+  author = {Seed, Alice},
+  title = {Seed Paper},
+  year = {2024},
+  doi = {10.1000/seed-doi}
+}
+"""
+        )
+
+        expander = CrossrefExpander()
+        expander.resolver.source_client.get_json = lambda _url: {  # type: ignore[method-assign]
+            "message": {
+                "reference": [
+                    {
+                        "unstructured": "Proceedings of the Artificial Life Workshop",
+                        "year": "2005",
+                    }
+                ]
+            }
+        }
+
+        results = expander.expand_entry_references(store, "seed2024")
+
+        assert [result.discovered_citation_key for result in results] == ["ref2005proceedings1"]
+        discovered = store.get_entry("ref2005proceedings1")
+        assert discovered is not None
+        assert discovered["entry_type"] == "inproceedings"
+    finally:
+        store.close()
+
+
 def test_crossref_expander_returns_empty_on_fetch_error():
     store = BibliographyStore()
     try: