HyperTaxonomy integration

WP-SKOS calls HyperTaxonomy through function-existence-guarded wrappers. It has no direct knowledge of TermConnect, As the Crow Flies, or any other plugin — all integrations are accessed through HyperTaxonomy public API.

Functions called

HyperTaxonomy function	Purpose
`htax_is_term_hidden( $term_id )`	Gate hidden terms: return 404 for unauthorized users; also filters hidden groups, child groups, and member concepts from Collections
`htax_get_included_terms( $term )`	Inclusions → `skos:related` and the `wpskos:includes` sub-property
`htax_get_container_terms( $term )`	Containers (reverse inclusions) → `skos:related` and the `wpskos:container` sub-property
`htax_get_synonym_terms( $term )`	Mutual inclusions → `skos:related` and the `wpskos:synonym` sub-property
`htax_get_related_terms( $term_id, $type )`	Custom relationship types (forward) → `skos:related` and typed sub-properties
`htax_get_reverse_related_terms( $term_id, $type )`	Custom relationship types (reverse) → typed `_reverse` sub-properties
`htax_get_registered_relationship_types( $include_custom )`	Enumerate custom relationship types and read their metadata (label, symmetry, source site)
`htax_get_redirect_target( $term_id )`	Detect redirect terms for `owl:deprecated` + `dct:isReplacedBy`
`htax_get_term_uris( $term_id )`	External URIs → `skos:closeMatch` (TermConnect populates via `htax_term_uris` filter)
`htax_get_term_locations( $term_id )`	Raw location rows → formatted to `schema:Place` objects inside wp-skos (ATCF provides the underlying data)
`htax_taxonomy_has_feature( $taxonomy, 'share_locations' )`	Gate `schema:location` on the per-taxonomy Share list of locations flag
`htax_get_expanded_term_ids( $term_id, true )`	Concept → expanded post set for the document search tax_query. The `true` flag also folds in terms that redirect to the concept, so a target concept’s documents include those tagged with its redirecting (deprecated) terms — matching the relevance index
`htax_get_term_external_posts( $term_id, $args )`	Related peer-site documents → `foaf:Document` results in document search; `$args` carries scope hints (platforms, foaf_depth, per_page) (TermConnect populates via `htax_term_external_posts`; HT gates visibility, so hidden concepts contribute nothing)
`htax_is_term_hidden( $term_id )` / `htax_can_see_hidden_terms( $taxonomy )`	Skip hidden concepts when resolving a document-search request (delegating the visibility decision to HT)
`htax_get_all_term_groups()`	Gate Collection endpoint availability (presence check)

Relevance ordering in the document search is not produced by a HyperTaxonomy function — wp-skos runs a direct SQL query against the wp_htax_search_terms index table to sum each candidate post’s strength over the expanded term set. The index stores strength per scoring model, so the query restricts rows to the model HyperTaxonomy uses for search (htax_strength_model_sql()). It also gates relationship_type per the concept’s taxonomy enabled features (mirroring HyperTaxonomy’s own scoring), and combines rows sharing a (post, term) pair via noisy-OR (1 − Π(1 − strength), regardless of source_term or relationship_type) before summing across terms — matching HyperTaxonomy’s term-strength scorers exactly: a term reached by only one path is unaffected, while a term reached by several distinct source terms scores higher without the combined value ever reaching the ceiling a single direct row can hit.

Collection membership (WP_SKOS_Builder::build_collection()) is the other direct SQL exception: it queries the wp_htax_term_relationships table for member_of rows pointing at the group, since HyperTaxonomy exposes no public function for “all terms that declare membership in this group.” Both direct queries are guarded with SHOW TABLES LIKE before running, so a HyperTaxonomy schema change degrades to an empty result (no relevance ordering / no Collection members) rather than a fatal error.

Feature flags checked

Flag	Effect when disabled
`share_locations`	`schema:location` omitted from concept documents

Cache invalidation hooks

Hook	Fired by	What WP-SKOS invalidates
`saved_term`	WordPress core	Both concept variants + scheme for that taxonomy
`delete_term`	WordPress core	Both concept variants + scheme for that taxonomy
`htax_includes_changed`	HyperTaxonomy	Both concept variants for the affected term
`htax_term_uris_changed`	HyperTaxonomy (relayed from TC)	Both concept variants for the affected term
`htax_term_locations_changed`	HyperTaxonomy (relayed from ATCF)	Both concept variants for the affected term

WP-SKOS does not depend on TermConnect or As the Crow Flies directly. HyperTaxonomy listens for tc_term_uris_changed and atcf_term_location_changed and re-fires them under its own namespace so downstream plugins only need to depend on HyperTaxonomy.

Cache

Concept documents are stored as WordPress transients with TTL 0 (persist until explicitly deleted):

Key pattern	Content
`wpskos_cpt_{term_id}_0`	Concept JSON-LD, unauthenticated view
`wpskos_cpt_{term_id}_1`	Concept JSON-LD, authenticated view (may include hidden linked concepts)
`wpskos_sch_{md5(taxonomy)}`	ConceptScheme JSON-LD

The two concept variants exist because hidden linked terms appear in skos:narrower / skos:related for privileged users but are suppressed for public visitors.

All transients and the wpskos_settings option are deleted when the plugin is uninstalled via the WordPress Plugins screen.

Multilingual labels

When a multilingual plugin is active, skos:prefLabel is an array with one entry per language:

"skos:prefLabel": [
  { "@value": "Electric Vehicles", "@language": "en" },
  { "@value": "Véhicules électriques", "@language": "fr" }
]

WP-SKOS builds the label map in get_pref_labels( WP_Term $term ), which detects multilingual plugins automatically: Polylang (via pll_get_term_translations()) and WPML (via the wpml_get_element_translations filter). Sites with no multilingual plugin get a single-entry array using the language tag from Settings → WP-SKOS.