> ## Documentation Index
> Fetch the complete documentation index at: https://arize-ax.mintlify.dev/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# How to Use GraphQL

GraphQL provides developers with the ability to build more powerful tools with precise and flexible queries. This represents an architectural and conceptual shift from the well-known REST API.

Since GraphQL is relatively new, you'll likely encounter unfamiliar terminology in the GraphQL API. Use this page as a recourse to help you navigate the necessary terminology and concepts to implement the Arize GraphQL API.

### Schema

A schema defines a GraphQL API's type system and resides on the GraphQL API server.

It describes the complete set of possible data (objects, fields, relationships, everything) that a client can access. Calls from the client are [validated](https://graphql.org/learn/validation/) and [executed](https://graphql.org/learn/execution/) against the schema. A client can find information about the schema via [introspection](https://graphql.org/learn/introspection/).

### Field

A field is a unit of data you can retrieve from an object. As the [official GraphQL docs](https://graphql.org/learn/schema/) notes that: "The GraphQL query language is basically about selecting fields on objects."

The [official spec](https://graphql.github.io/graphql-spec/June2018/#sec-Language.Fields) also details the following:

> All GraphQL operations must specify their selections down to fields which return scalar values to ensure an unambiguously shaped response.

This means that if you try to return a field that is not a scalar, schema validation it will throw an error. There must be nested subfields added until all fields return scalars.

### Argument

An argument is a set of key-value pairs attached to a specific field. Some fields require an argument. [Mutations](https://graphql.org/learn/queries/#mutations) require an input object as an argument.

### Implementation

A GraphQL schema may use the term *implements* to define how an object inherits from an [interface](https://graphql.org/learn/schema/#interfaces).

Here's a contrived example of a schema that defines interface `X` and object `Y`:\\

```typescript theme={null}
interface X {
  some_field: String!
  other_field: String!
}

type Y implements X {
  some_field: String!
  other_field: String!
  new_field: String!
}
```

This means object `Y` requires the same fields/arguments/return types that interface `X` does, while adding new fields specific to object `Y`. (The `!` means the field is required.)

### Connection

Connections let you query related objects as part of the same call. With connections, you can use a single GraphQL call where you would have to use multiple calls to a REST API.

It's helpful to picture a graph: dots connected by lines. The dots are nodes, the lines are edges. A connection defines a relationship between nodes.

### Edge

Edges represent connections between nodes. When you query a connection, you traverse its edges to get to its nodes. Every `edges` field has a `node` field and a `cursor` field. Cursors are used for [pagination](https://graphql.org/learn/pagination/).

### Node

*Node* is a generic term for an object. You can look up a node directly, or you can access related nodes via a connection. If you specify a `node` that does not return a [scalar](https://graphql.org/learn/schema/#interfaces), you must include subfields until all fields return scalars.

### Discovering the GraphQL API

GraphQL is [introspective](https://graphql.org/learn/introspection/). This means you can query a GraphQL schema for details about itself.

Query `__schema` to list all types defined in the schema and get details about each:

```
query {
  __schema {
    types {
      name
      kind
      description
      fields {
        name
      }
    }
  }
}
```

Query `__type` to get details about any type:

```javascript theme={null}
query {
  __type(name: "Model") {
    name
    kind
    description
    fields {
      name
    }
  }
}
```

<Info>
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