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The /topics endpoints expose Hexagraph’s registry of research topics. Topics represent fine-grained areas of scholarly research derived from clusters of related publications. Each topic contains descriptive metadata, scholarly output metrics, citation counts, associated domain classifications, and relationships to similar topics. Topics are identified using the OA:T prefix system.

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List topics

Retrieve a paginated list of research topics.

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Query Parameters

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page (number)

Page number for paginated results. Starts at 1.

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per_page (number)

Number of results returned per page. Maximum value is 200.

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sort (number)

Sort results by scholarly output count. Available values:
ValueDescription
1Sort by outputs ascending
-1Sort by outputs descending

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filter (string)

Filter results using one or more key-value expressions. Multiple filters may be combined using commas.

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group_by (string)

Group results by a specified field for aggregation and analysis.

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Example Request

curl "https://hexagraph-core.onrender.com/topics"

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Example Response

[
  {
    "id": "OA:T14423",
    "name": "Military Technology and Strategies",
    "description": "This cluster of papers covers various aspects related to the modernization and development of air force capabilities...",
    "outputs": 22341643,
    "citations": 830569,
    "domain": [
      "Physical Sciences"
    ],
    "field": [
      "Engineering"
    ],
    "subfield": [
      "Aerospace Engineering"
    ],
    "siblings": [
      "Antenna Design and Analysis",
      "Robotics and Sensor-Based Localization",
      "Nuclear reactor physics and engineering"
    ]
  },
  {
      "id": "OA:T10346",
      "name": "Magnetic confinement fusion research",
      "description": "This cluster of papers covers a wide range of topics in plasma physics and fusion research, including turbulence, transport, MHD stability, edge localized modes, zonal flows, confinement, neoclassical tearing modes, energetic particles, and diagnostics. The research spans from theoretical modeling to experimental observations in various fusion devices.",
      "outputs": 9281567,
      "citations": 2575385,
      "domain": [
        "Physical Sciences"
      ],
      "field": [
        "Physics and Astronomy"
      ],
      "subfield": [
        "Nuclear and High Energy Physics"
      ],
      "siblings": [
        "Black Holes and Theoretical Physics",
        "Particle physics theoretical and experimental studies"
      ]
    }
]

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Get a single topic

Fetch a specific topic by its OA:T identifier.

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Example Request

curl "https://hexagraph-core.onrender.com/topics/OA:T14423"

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Example Response

{
  "id": "OA:T14423",
  "name": "Military Technology and Strategies",
  "description": "This cluster of papers covers various aspects related to the modernization and development of air force capabilities...",
  "keywords": [
    "Air Force",
    "Modernization",
    "Warfare",
    "Unmanned Aerial Vehicles",
    "Radar Systems"
  ],
  "outputs": 22341643,
  "citations": 830569,
  "domain": {
    "id": "OA:3",
    "name": "Physical Sciences"
  },
  "field": {
    "id": "OA:22",
    "name": "Engineering"
  },
  "subfield": {
    "id": "OA:2202",
    "name": "Aerospace Engineering"
  },
  "wikipedia": "https://en.wikipedia.org/wiki/Air_force_modernization",
  "siblings": [
    {
      "id": "OA:T10069",
      "name": "Antenna Design and Analysis"
    }
  ]
}

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Response Fields

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id

Unique identifier for the topic. Uses the OA:T prefix system (e.g. OA:T14423).

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name

Display name of the research topic.

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description

Summary describing the research area represented by the topic.

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outputs

Total number of scholarly outputs associated with the topic.

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citations

Aggregate citation count across all works associated with the topic.

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keywords

A list of representative keywords associated with the topic. Only available in the single-topic endpoint.

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domain

The parent research domain associated with the topic. In the list endpoint, domains are returned as an array of names. 
{
  "domain": ["Physical Sciences"]
}
In the single-topic endpoint, the domain is returned as an object.

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domain.id

Unique identifier of the parent domain.

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domain.name

Display name of the parent domain.

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field

The parent research field associated with the topic. In the list endpoint, fields are returned as an array of names. 
{
  "field": ["Engineering"]
}
In the single-topic endpoint, the field is returned as an object.

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field.id

Unique identifier of the parent field.

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field.name

Display name of the parent field.

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subfield

The parent research subfield associated with the topic. In the list endpoint, subfields are returned as an array of names. 
{
  "subfield": ["Aerospace Engineering"]
}
In the single-topic endpoint, the subfield is returned as an object.

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subfield.id

Unique identifier of the parent subfield.

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subfield.name

Display name of the parent subfield.

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wikipedia

Wikipedia article associated with the topic, when available. Only available in the single-topic endpoint.

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siblings

Related topics that belong to a similar area of research. In the list endpoint, siblings are returned as an array of topic names. In the single-topic endpoint, siblings are returned as objects containing:

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siblings[].id

Unique identifier of the related topic.

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siblings[].name

Display name of the related topic.