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github-actions[bot] edited this page Sep 2, 2026 · 1 revision

Material dropdown

Picks what the sample was taken from: groundwater, soil, tissue, and so on. Multi select. Leaving it empty means "any material".

Material dropdown

What it does

It sits directly under the Substance dropdown in the query editor, and appears whenever the entity type is Samples, inside + Add Filters.

Like Substance, the list comes from the data rather than a fixed list, sorted by how many observations use each material, with the count in brackets: GROUNDWATER (609496). Unfiltered it returns 171 distinct material types across the whole graph. Labels come straight from the graph, so they arrive in whatever case the source used. Maine data shouts in uppercase (GROUNDWATER, WASTE WATER), water quality portal data is title case (Tissue, Water). That inconsistency is upstream, not a rendering bug.

The list is region aware in the same way Substance is. Pick Cumberland County in Maine and it narrows from 171 entries to 25.

Two quirks worth knowing about before you trust what you see:

  • "Material" is looser than it sounds. The query keeps anything a sample was recorded as being made of, which in the water quality portal data includes biological taxa. Selecting Cumberland County surfaces Mytilus edulis, the blue mussel, sitting in the list next to GROUNDWATER. That is what the graph says, and the filter only excludes URIs outside the http://w3id.org/ namespace.
  • The URIs change with the region. Without a region the query hits sawgraph, which names groundwater me-egad#sampleMaterialType.GW. With a region it hits federation, which names the same thing me-egad-data#sampleMaterialType.GW. Same label, different URI. A selection made before picking a state will therefore not match anything after picking one. See If it looks wrong.

The SPARQL query

Endpoint is sawgraph with no region, federation once a state is picked. Unlike the Substance query, the two variants are not the same query with a pattern spliced in. They are written separately, and the difference matters.

Without a region

SELECT ?matType (SAMPLE(?_label) AS ?label) (COUNT(DISTINCT ?observation) AS ?num)
WHERE {
  ?observation rdf:type coso:ContaminantObservation ;
               coso:analyzedSample ?sample .
  ?sample coso:sampleOfMaterialType ?matType .
  OPTIONAL { ?matType rdfs:label ?_label . }
  FILTER(STRSTARTS(STR(?matType), "http://w3id.org/"))
} GROUP BY ?matType
ORDER BY DESC(?num) ?label

Line by line:

  • ?observation rdf:type coso:ContaminantObservation is every recorded measurement.
  • coso:analyzedSample ?sample is the physical sample that measurement was run on. This is the extra hop compared to Substance, which reads the chemical straight off the observation.
  • ?sample coso:sampleOfMaterialType ?matType is what that sample was made of.
  • OPTIONAL { rdfs:label } because not every material type has a label. Ones that do not fall back to the tail of their URI, done in the hook rather than in SPARQL.
  • The FILTER drops anything outside the w3id.org namespace, which is the crude way this query keeps out URIs from source vocabularies that were never meant to be shown.

Note that this variant never touches sample points at all. It walks observation to sample to material and stops.

With a region

SELECT ?matType (SAMPLE(?_label) AS ?label) (COUNT(DISTINCT ?observation) AS ?num)
WHERE {
  ?sp rdf:type coso:SamplePoint .
  ?sp spatial:connectedTo ?_region .
  ?_region rdf:type kwg-ont:AdministrativeRegion_3 ;
           kwg-ont:administrativePartOf+ ?_regionRoot .
  VALUES ?_regionRoot { kwgr:administrativeRegion.USA.23005 }
  ?observation rdf:type coso:ContaminantObservation ;
               coso:observedAtSamplePoint ?sp ;
               coso:analyzedSample ?sample .
  ?sample coso:sampleOfMaterialType ?matType .
  OPTIONAL { ?matType rdfs:label ?_label . }
  FILTER(STRSTARTS(STR(?matType), "http://w3id.org/"))
} GROUP BY ?matType
ORDER BY DESC(?num) ?label

The added part is the same region pattern the Substance dropdown uses, plus the coso:observedAtSamplePoint hop that connects an observation to a place. 23005 is Cumberland County, Maine. A whole state selection uses the two digit code instead, and the administrativePartOf+ walk covers everything underneath it either way.

Verified against the live endpoints. Unfiltered returns 171 material types, led by GROUNDWATER at 609496 observations, then Tissue at 96272 and Water at 95779. Cumberland County returns 25.

How it is wired up

Cached under ['materialTypes', <region key>] with staleTime: Infinity and retry: 1, so one fetch per region per session. As with Substance, the fallback doubles as placeholderData, and the empty result handling is asymmetric: with no region the fallback is returned, with a region an empty list is.

The missing label fallback happens in the hook, at useDiscoveryQueries.ts:132, by splitting the URI on # or / and taking the tail.

If it looks wrong

Exactly six materials with tidy title case labels and no counts. That is FALLBACK_MATERIAL_TYPES. Real results shout in uppercase and carry counts.

A selection stops matching after picking a state. This is the me-egad versus me-egad-data URI split described above. The two endpoints name the same material differently, and the stored selection is a URI. Reselect the material after setting the region.

Species names in a materials list. Genuinely in the graph, under us-wqp-data#biologicalTaxon.*. The namespace filter does not exclude them. If they should not be offered, the filter needs to be narrower than http://w3id.org/.

Labels that are URI tails, like sampleMaterialType.WW. That material has no rdfs:label, so the hook fell back to the URI tail.

Empty after picking a county. No observations recorded there. Expected.

See also

SAWGraph Explorer

Home

Dropdowns

In the repo

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