> For the complete documentation index, see [llms.txt](https://docs.sdv.dev/sdv/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.sdv.dev/sdv/~/changes/T3ZD1DOoRUEqkmrAGBZp/reference/metadata-spec/sequential-metadata-json.md).

# Sequential Metadata JSON

This guide describes the sequential metadata JSON spec. 

<figure><img src="/files/tdvX2emldgh3F9LBcyfp" alt=""><figcaption><p>An example of sequential data. There are multiple sequences (one for each Patient ID). Within each sequence is an ordered set of rows.</p></figcaption></figure>

<details>

<summary>Click to see the metadata JSON</summary>

```json
{
    "METADATA_SPEC_VERSION": "SINGLE_TABLE_V1",
    "sequence_key": "Patient ID",
    "sequence_index": "Time",
    "columns": {
        "Patient ID": { "sdtype": "id", "regex_format": "ID_[0-9]{3}" },
        "Address": { "sdtype": "physical_address", "pii": true },
        "Smoker": { "sdtype": "boolean" },
        "Time": { "sdtype": "datetime", "datetime_format": "%m/%d/%Y" },
        "Heart Rate": { "sdtype": "categorical" },
        "Systolic BP": { "sdtype": "numerical" }
    }
}
```

</details>

{% hint style="success" %}
**Create your metadata programmatically.** Use the [Python API](/sdv/~/changes/T3ZD1DOoRUEqkmrAGBZp/single-table-data/data-preparation/single-table-metadata-api.md) to automatically detect the metadata based on your data.
{% endhint %}

## Overview

{% hint style="success" %}
The JSON for a sequential table is the same as the single table JSON with some added elements.

**See** [**Single Table JSON**](/sdv/~/changes/T3ZD1DOoRUEqkmrAGBZp/reference/metadata-spec/single-table-metadata-json.md) **for more details.**
{% endhint %}

## Sequence Specific Concepts

You can optionally include additional metadata related to your sequences.

**`"sequence_key"`**: A column name of the sequence key, if you have multi-sequence data

{% hint style="info" %}
The **sequence key** is a column that identify which row(s) belong to which sequences. This is usually an ID column but it may also be a PII sdtype (such as `"phone_number"`).&#x20;

This is important for tables that contain multiple sequences. In our example, the sequence key is `'Patient ID'` because this column is used to break up the sequences.

If you don't supply a sequence key, the SDV assumes that your table only contains a single sequence. *Note: The SDV sequential models do not fully support single sequence data.*
{% endhint %}

**`"sequence_index"`**: A column name of the sequence index, if you have sequential data

{% hint style="info" %}
The **sequence index** determines the spacing between the rows in a sequence. Use this if you have an explicit index such as a timestamp. If you don't supply a sequence index, the SDV assumes there is equal spacing of an unknown unit.
{% endhint %}


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