Source: https://databento.com/docs/datasets/xnas-basic


# Nasdaq Basic with NLS Plus

**Dataset ID**: [XNAS.BASIC]($PLATFORM_HOSTNAME/catalog/us-equities#XNAS.BASIC)

Nasdaq disseminates top-of-book data via their QBBO feed, and last sale data via their NLS and NLS+ feeds.
Databento receives these over UDP multicast in our NY4 data center.
Because they come from separate feeds, BBO and trade events may be out-of-order, even within a single instrument.

PDF specifications are available on Nasdaq's website for the [QBBO](https://www.nasdaqtrader.com/content/technicalsupport/specifications/dataproducts/QBBOSpecification2.1.pdf), [NLS](https://www.nasdaqtrader.com/content/technicalsupport/specifications/dataproducts/NLSSpecification3.0.pdf) and [NLS+](https://www.nasdaqtrader.com/content/technicalsupport/specifications/dataproducts/NLSPlus-cloud.pdf) feeds.

### Symbol convention

Raw symbols in this dataset use the **Nasdaq** convention (e.g. `BRK.B`, `AAC+`).
See [CMS vs. Nasdaq symbology](https://databento.com/docs/conventions/symbology.md#raw-symbol) for the per-dataset convention map.

### Timestamps

Nasdaq Basic messages received by Databento have at most one timestamp, which has nanosecond precision.
As with all of our datasets, we also collect a `ts_recv` timestamp when the packet was received by our capture server.

The extra field `ts_in_delta` does not convey any additional information for this dataset, and is equivalent to `ts_recv - ts_event`.

| Databento Field | TotalView Field | Description |
| `ts_recv` | N/A | The capture-server-received timestamp. |
| `ts_event` | Timestamp | The matching-engine-received timestamp. |

More details about our timestamps are available in our [timestamping guide](https://databento.com/docs/architecture/timestamping-guide.md).

### Source feeds

Nasdaq Basic is composed of data from the Nasdaq QBBO and Nasdaq NLS+ feeds.

### Venues

Nasdaq Basic contains trade data for the following venues:
- Nasdaq (XNAS)
- Nasdaq PSX (XPSX)
- Nasdaq Texas (XBOS)
- FINRA/Nasdaq TRF Carteret (FINN)
- FINRA/Nasdaq TRF Chicago (FINC)

However, only quotes for Nasdaq (XNAS) are provided.

The `publisher_id` field on every record from Databento can be used to identify the venue associated with the event.

Because Nasdaq PSX, Nasdaq Texas, and the TRF facilities do not have a BBO disseminated by Nasdaq QBBO, the [MBP-1](https://databento.com/docs/schemas/mbp-1.md), [BBO](https://databento.com/docs/schemas/bbo.md) and [TBBO](https://databento.com/docs/schemas/tbbo.md) schemas are not available.
Instead, the equivalent consolidated schemas are provided: [CMBP-1](https://databento.com/docs/schemas/mbp-1.md#consolidated-market-by-price-cmbp-1), [CBBO](https://databento.com/docs/schemas/bbo.md#consolidated-bbo-on-interval-cbbo) and [TCBBO](https://databento.com/docs/schemas/tbbo.md#consolidated-bbo-on-trade-tcbbo).

### Normalization

There are only **A**dd and **T**rade actions for Nasdaq Basic.

**T**rade records are normalized from NLS+ *Trade Report for Non-NextShares* or *Long form Trade Report for Non-NextShares* messages.
The `publisher_id` field will identify the venue associated with the trade.
There is no information about the side of the trade, so `side` will always be `N`.

**A**dd records are normalized from Nasdaq QBBO *Quotation Message*.
An **A** record will be published anytime the best bid or offer quote is updated.
The `publisher_id` field will always be set to 93 (`XNAS_BASIC_EQUS`)

### Definition normalization

Definition records are sourced from NLS+ *Stock Directory* messages.

| Databento Field | NLS+ Field | Description |
| `exchange` | Market Category | Normalized to the MIC code of the listing venue. All Nasdaq-listed instruments will normalize to `XNAS`. |
| `security_type` | Issue Classification | Identifies the security class for the issue as assigned by Nasdaq. A list of the different values and their meanings can be found in Appendix E [here](https://www.nasdaqtrader.com/content/technicalsupport/specifications/dataproducts/NLSPlusSpecification3.0.pdf). |
| `secsubtype` | Issue Sub-Type | Identifies the security sub-type for the issue as assigned by Nasdaq. A list of the different values and their meanings can be found in Appendix F [here](https://www.nasdaqtrader.com/content/technicalsupport/specifications/dataproducts/NLSPlusSpecification3.0.pdf). |

### Statistics normalization

Statistics records are sourced from NLS+ *Trade Report for Non-NextShares* messages.
Databento provides the opening price and closing price statistics based on the sale condition field of these trade messages.

### Flags normalization

The `F_PUBLISHER_SPECIFIC` flag provides no additional meaning in this dataset and can be safely ignored.