[jira] [Resolved] (TIKA-4794) Normalize/simplify metadata keys in 4.x

["Tim Allison (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/TIKA-4794?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Tim Allison resolved TIKA-4794.
-------------------------------
    Fix Version/s: 4.0.0
       Resolution: Fixed

> Normalize/simplify metadata keys in 4.x
> ---------------------------------------
>
>                 Key: TIKA-4794
>                 URL: https://issues.apache.org/jira/browse/TIKA-4794
>             Project: Tika
>          Issue Type: Task
>            Reporter: Tim Allison
>            Priority: Major
>             Fix For: 4.0.0
>
>
> *Background*
> Tika's metadata keys are inconsistent, and 4.0.0 is the last free break until 5.0 (whatever ships is frozen for the 4.x line):
>  * Tika's own keys are scattered across ~8 prefixes (X-TIKA:, tika:, tika_pg:, rendering:, signature:, imagereader:, bare hasSignature/embeddedResourceType), with 3+ casings inside X-TIKA: alone (snake, camel, Title-Hyphen, UPPER sub-namespaces).
>  * resourceName shipped half-migrated (bare → X-TIKA:resourceName) — the worst state.
>  * The metadata object is also a control plane (media type drives routing, resourceName drives detection, X-TIKA:* carries provenance/digests), but the boundary is convention only: a crafted file can inject or overwrite Tika's own keys.
>  * Format namespaces mix casings; QuattroPro reuses WordPerfect's prefix (collision); there's no rule for "is this key Tika's or the file's".
> Options
>  #  Leave as-is. Ship the inconsistency + half-migrated resourceName + convention-only boundary; frozen until 5.x
>  #  tk:. Consolidate every Tika-asserted key under one kebab-cased tk: prefix; finish resourceName → tk:resource-name; add a reserved-namespace trust boundary. Format namespaces untouched.
>  #  tk: + kebab. Everything in (2), plus apply the casing rule inside the format namespaces.
> *Guiding principles (2 and 3)*
>   1. Who asserted the key? Tika-computed → owned, normalized, trusted. File/standard-authored → verbatim (the spelling/capitalization is the interop contract).
>   2. Match enforcement to stakes. Control-plane / Tika-native keys → reserved, writable only via a Property; cosmetic drift → convention.
>   3. Casing follows key-name authorship, not the namespace (the prefix is just the domain). Tika coined the name → kebab; a standard/file authored it → verbatim.
>   4. Clean 3→4 break, documented with a migration table; no auto-remap machinery.
>   *2 — tk: (rationale + consistency)*
>   One prefix, one casing for everything Tika asserts, replacing the 8 scattered prefixes and their mixed casings; resourceName finished. tk: (and legacy X-TIKA: ) become reserved: a String write to them is dropped unless trusted, so a scraped file can't forge Tika's routing/provenance/digest/content keys or inject fake tk:chunks embeddings — enforced once in tika-core, not per-parser discipline. Consistency: any Tika key is now predictable (tk: + kebab), and the trust boundary is mechanism rather than convention.
>   *3 — tk: + kebab (rationale + consistency)*
>   Extends "Tika-coined → kebab" into the format namespaces (e.g. pdf:hasMarkedContent → pdf:has-marked-content, zip:compressedSize → zip:compressed-size, access_permission: →  access-permission: ). Names from a standard stay verbatim (dc:, xmp:, EXIF/tiff:, MAPI, email headers, ECMA-376 OOXML props, PDF/A/X sub-namespaces) — re-casing them would break round-trip/interop. Also fixes the QuattroPro/WordPerfect prefix collision. Consistency: a Tika-authored key is kebab wherever it lives (under tk: or a format prefix); a  standard/file key keeps its source spelling — one rule answers casing everywhere.
>  
> If we did steps 2 or 3, we'd probably want to release a 4.0.0-beta-2.
>  
> Steps 2 or 3 would be fairly major changes for downstream users, but it would allow us to clean up years of metadata key name bloat.



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