Dropdowns County

County dropdown

Narrows a query to specific counties inside the chosen state. Multi select. Leaving it empty means the whole state.

What it does

It lives in the Region selector, directly under the State dropdown, and only renders once a state has been picked. Before that there is nothing sensible to show, so it is not there at all.

The list is fetched fresh for each state, sorted alphabetically by name. Labels arrive from the graph fully qualified, as Androscoggin County, Maine rather than Androscoggin, and are shown as is.

While the fetch is in flight the select shows its loading state, wired straight from the hook's isLoading. This is the only discovery dropdown that surfaces loading at all, and the reason is the next paragraph.

There is no fallback list. Every other query backed dropdown has hardcoded defaults to fall back on. This one does not, because a wrong county list is worse than no county list: you would be offering filters that silently match nothing. If the endpoint fails you get an empty dropdown.

The county code the app actually uses is not returned by the query. It is derived on the client by taking the county URI and splitting on dots, so kwgr:administrativeRegion.USA.23005 becomes 23005. That five digit FIPS code is what downstream pipeline queries put into their VALUES clauses.

The SPARQL query

Endpoint is spatialkg. No region variant, since the state code is the whole point.

SELECT DISTINCT ?county ?countyName WHERE {
  ?county kwg-ont:administrativePartOf kwgr:administrativeRegion.USA.23 ;
          rdfs:label ?countyName .
  FILTER(STRSTARTS(STR(?county), STR(kwgr:)))
} ORDER BY ?countyName

Line by line:

• ?county kwg-ont:administrativePartOf kwgr:administrativeRegion.USA.23 finds everything that is administratively part of Maine. The 23 is substituted with whichever state FIPS code was selected.
• Note there is no + on that predicate, unlike the sample point region pattern used by the Substance and Material queries. A single hop from the state lands exactly on counties, which is what makes this query short. Adding + would pull in sub county divisions too.
• rdfs:label ?countyName is the display name.
• The FILTER keeps only URIs in the KnowledgeWeb Graph resource namespace. Other graphs describe the same counties under their own URIs, and without this the dropdown would list each county several times.
• ORDER BY ?countyName gives the alphabetical ordering. DISTINCT guards against a county carrying more than one matching label.

Verified against the live endpoint. Maine returns its counties in order, starting Androscoggin, Aroostook, Cumberland.

How it is wired up

• The control is a shared FlatSelect, rendered at RegionSelector.tsx:47, inside a block that only renders when a state is set.
• Its options come from useCounties(stateCode), called at RegionSelector.tsx:12.
• The query text is built by buildDiscoverCountiesQuery().
• It runs through executeSparql() against the spatialkg URL in endpoints.ts.
• The state list feeding it is static, ALL_US_STATES and AVAILABLE_STATE_FIPS in regions.ts.

Cached under ['counties', <stateCode>] with staleTime: Infinity and gated by enabled: !!stateCode, so nothing fires until a state exists. No placeholderData and no retry override, which is what makes the loading state visible here and invisible elsewhere.

The code derivation happens at useDiscoveryQueries.ts:151.

If it looks wrong

No County dropdown at all. No state is selected. It is conditionally rendered, not disabled.

Empty after picking a state. Either the spatialkg endpoint is down, or that state has no administrative regions loaded. There is no fallback to mask it, so an empty list here is always worth investigating. Check the browser network tab for the request.

Stuck showing the loading state. The request has not resolved. Unlike the other dropdowns there is no placeholder data underneath it, so a slow endpoint is visible rather than hidden.

Duplicate counties. The namespace FILTER is not doing its job, which would mean the same county is described more than once inside the KWG resource namespace itself.

A county selection matches nothing downstream. Check the derived code. The client takes everything after the last dot in the URI, so a URI shaped differently than administrativeRegion.USA.23005 would yield garbage.

See also

• Dropdowns, the index of all filter controls
• Dropdowns Substance and Dropdowns Material, both of which consume the selected county codes