# Roadmap

Major unimplemented features (as of September 2018) include:

- backend "soundness" work to ensure corrupt data model states aren't reachable
  via the API
- authentication and account creation
- rate-limiting and spam/abuse mitigation
- "automated update" bots to consume metadata feeds (as opposed to one-time
  bulk imports)
- actual entity creation, editing, deleting through the web interface
- updating the search index in near-real-time following editgroup merges. In
  particular, the cache invalidation problem is tricky for some relationships
  (eg, updating all releases if a container is updated)

Once a reasonable degree of schema and API stability is attained, contributions
would be helpful to implement:

- import (bulk and/or continuous updates) for more metadata sources
- better handling of work/release distinction in, eg, search results and
  citation counting
- de-duplication (via merging) for all entity types
- matching improvements, eg, for references (citations), contributions
  (authorship), work grouping, and file/release matching
- internationalization of the web interface (translation to multiple languages)
- review of design for accessibility
- better handling of non-PDF file formats

Longer term projects could include:

- full-text search over release files
- bi-directional synchronization with other user-editable catalogs, such as
  Wikidata
- better representation of multi-file objects such as websites and datasets
- altenate/enhanced backend to store full edit history without overloading
  traditional relational database

## Known Issues

Too many right now, but this section will be populated soon.

- changelog index may have gaps due to postgresql sequence and transaction
  roll-back behavior

## Unresolved Questions

How to handle translations of, eg, titles and author names? To be clear, not
translations of works (which are just separate releases), these are more like
aliases or "originally known as".

Are bi-directional links a schema anti-pattern? Eg, should "work" point to a
"primary release" (which itself points back to the work)?

Should `identifier` and `citation` be their own entities, referencing other
entities by UUID instead of by revision? Not sure if this would increase or
decrease database resource utilization.

Should contributor/author affiliation and contact information be retained? It
could be very useful for disambiguation, but we don't want to build a huge
database for spammers or "innovative" start-up marketing.

Can general-purpose SQL databases like Postgres or MySQL scale well enough to
hold several tables with billions of entity revisions? Right from the start
there are hundreds of millions of works and releases, many of which having
dozens of citations, many authors, and many identifiers, and then we'll have
potentially dozens of edits for each of these, which multiply out to `1e8 * 2e1
* 2e1 = 4e10`, or 40 billion rows in the citation table. If each row was 32
bytes on average (uncompressed, not including index size), that would be 1.3
TByte on its own, larger than common SSD disks. I do think a transactional SQL
datastore is the right answer. In my experience locking and index rebuild times
are usually the biggest scaling challenges; the largely-immutable architecture
here should mitigate locking. Hopefully few indexes would be needed in the
primary database, as user interfaces could rely on secondary read-only search
engines for more complex queries and views.

There is a tension between focus and scope creep. If a central database like
fatcat doesn't support enough fields and metadata, then it will not be possible
to completely import other corpuses, and this becomes "yet another" partial
bibliographic database. On the other hand, accepting arbitrary data leads to
other problems: sparseness increases (we have more "partial" data), potential
for redundancy is high, humans will start editing content that might be
bulk-replaced, etc.

There might be a need to support "stub" references between entities. Eg, when
adding citations from PDF extraction, the cited works are likely to be
ambiguous. Could create "stub" works to be merged/resolved later, or could
leave the citation hanging. Same with authors, containers (journals), etc.