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+
+These are notes on how bibliographic metadata matches (of records) and
+slugification (to create lookup keys on title strings) worked in the past in
+the sandcrawler repository. Eg, circa 2018.
+
+## Scala Slug-ification
+
+Original title strings longer than 1023 characters were rejected (before
+slug-ifying).
+
+There was a "slug-denylist". Additionally, scorable strings needed to be
+between 8 and 1023 characters (not bytes) long (inclusive)
+
+Slugification transform was:
+
+- lower-case
+- remove whitespace ("\s")
+- strip specific accent characters:
+    '\u0141' -> 'L',
+    '\u0142' -> 'l',  // Letter ell
+    '\u00d8' -> 'O',
+    '\u00f8' -> 'o'
+- remove all '\p{InCombiningDiacriticalMarks}'
+- remove punctuation:
+    \p{Punct}
+    ’·“”‘’“”«»「」¿–±§
+
+Partially adapted from apache commons: <https://git-wip-us.apache.org/repos/asf?p=commons-lang.git;a=blob;f=src/main/java/org/apache/commons/lang3/StringUtils.java;h=1d7b9b99335865a88c509339f700ce71ce2c71f2;hb=HEAD#l934>
+
+My original notes/proposal:
+
+1. keep only \p{Ideographic}, \p{Alphabetic}, and \p{Digit}
+2. strip accents
+3. "lower-case" (unicode-aware)
+4. do any final custom/manual mappings
+
+Resulting slugs less than 8 characters long were rejected, and slugs were
+checked against a denylist.
+
+Only 554 entries in the denylist; could just ship that in the library.
+
+
+## Python Tokenization
+
+- "&apos;" -> "'"
+- remove non "isalnum()" characters
+- encode as ASCII; this removes diacritics etc, but also all non-latin character sets
+- optionally remove all whitespace
+
+
+## Python GROBID Cleanups
+
+These are likely pretty GROBID-specific. Article title was required, but any of
+the other filtered-out fields just resulted in partial metadata. These filters
+are the result of lots of manual verification of results, and doing things like
+taking truncating titles and looking at the most popular prefixes for a large
+random sample.
+
+Same denylist for title slugs as Scala, plus:
+
+    editorial
+    advertisement
+    bookreviews
+    reviews
+    nr
+    abstractoriginalarticle
+    originalarticle
+    impactfactor
+    articlenumber
+
+Other filters on title strings (any of these bad):
+
+- 500 or more characters long
+- tokenized string less than 10 characters
+- tokenized starts with 'nr' or 'issn'
+- lowercase starts with 'int j' or '.int j'
+- contains both "volume" and "issue"
+- contains "downloadedfrom"
+- fewer than 2 or more than 50 tokens (words)
+- more than 12 tokens only a single character long
+- more than three ":"; more than one "|"; more than one "."
+
+Remove title prefixes (but allow):
+
+    "Title: "
+    "Original Article: "
+    "Original Article "
+    "Article: "
+
+Denylist for authors:
+
+    phd
+    phdstudent
+
+Journal name processing:
+
+- apply title denylist
+- remove prefixes
+    characters: /~&©
+    Original Research Article
+    Original Article
+    Research Article
+    Available online www.jocpr.com
+- remove suffixes
+    Available online at www.sciarena.com
+    Original Article
+    Available online at
+    ISSN
+    ISSUE
+- remove anywhere
+    e-ISSN
+    p-ISSN
+
+## Python Grouping Comparison
+
+Would consume joined groups, row-by-row. At most 10 matches per group; any more
+and skip (this was for file-to-release).
+
+Overall matching requirements:
+
+- string similarity threshold from scala code
+    https://oldfashionedsoftware.com/2009/11/19/string-distance-and-refactoring-in-scala/
+    https://stackoverflow.com/questions/955110/similarity-string-comparison-in-java/16018452#16018452
+- authors should be consistent
+    - convert one author list into space-separated tokens
+    - remove "jr." from all author token lists
+    - the last word for each author full name in the other list (eg, the lastname),
+      tokenized, must be in the token set
+- if both years defined, then must match exactly (integers)
+
+In the code, there is a note:
+
+    Note: the actual importer/merger should filter the following patterns out:
+    - container title has "letter" and "diar"
+    - contribs (authors) contain "&NA;"
+    - dates differ (not just year)
+
+
+## Scala Metadata Keys
+
+Only the titles were ever actually used (in scala), but the keys allowed were:
+
+- title
+- authors (list of strings)
+- year (int)
+- contentType
+- doi
+