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+status: deployed
+
+XML Fulltext Ingest
+====================
+
+This document details changes to include XML fulltext ingest in the same way
+that we currently ingest PDF fulltext.
+
+Currently this will just fetch the single XML document, which is often lacking
+figures, tables, and other required files.
+
+## Text Encoding
+
+Because we would like to treat XML as a string in a couple contexts, but XML
+can have multiple encodings (indicated in an XML header), we are in a bit of a
+bind. Simply parsing into unicode and then re-encoding as UTF-8 could result in
+a header/content mismatch. Any form of re-encoding will change the hash of the
+document. For recording in fatcat, the file metadata will be passed through.
+For storing in Kafka and blob store (for downstream analysis), we will parse
+the raw XML document (as "bytes") with an XML parser, then re-output with UTF-8
+encoding. The hash of the *original* XML file will be used as the key for
+referring to this document. This is unintuitive, but similar to what we are
+doing with PDF and HTML documents (extracting in a useful format, but keeping
+the original document's hash as a key).
+
+Unclear if we need to do this re-encode process for XML documents already in
+UTF-8 encoding.
+
+## Ingest Worker
+
+Could either re-use HTML metadata extractor to fetch XML fulltext links, or
+fork that code off to a separate method, like the PDF fulltext URL extractor.
+
+Hopefully can re-use almost all of the PDF pipeline code, by making that ingest
+worker class more generic and subclassing it.
+
+Result objects are treated the same as PDF ingest results: the result object
+has context about status, and if successful, file metadata and CDX row of the
+terminal object.
+
+TODO: should it be assumed that XML fulltext will end up in S3 bucket? or
+should there be an `xml_meta` SQL table tracking this, like we have for PDFs
+and HTML?
+
+TODO: should we detect and specify the XML schema better? Eg, indicate if JATS.
+
+
+## Persist Pipeline
+
+### Kafka Topic
+
+sandcrawler-ENV.xml-doc
+    similar to other fulltext topics; JSON wrapping the XML
+    key compaction, content compression
+
+### S3/SeaweedFS
+
+`sandcrawler` bucket, `xml` folder. Extension could depend on sub-type of XML?
+
+### Persist Worker
+
+New S3-only worker that pulls from kafka topic and pushes to S3. Works
+basically the same as PDF persist in S3-only mode, or like pdf-text worker.