# Data sources

In the ENLYZE Manufacturing Data Platform (MDP), a data source represents a virtual or physical OT device that is connected to the ENLYZE MDP via a connector to collect process data. Examples of data sources include programmable logic controllers (PLCs) such as the Siemens S7-1200, Modbus energy meters, or OPC-DA and OPC-UA servers running on industrial PCs (IPCs).

While energy meters are typically connected only via Modbus, PLCs like the Siemens S7-1200 support connections using various protocols, such as the native OMS+ (S7+) and OPC-UA.

Process data is collected from a data source by selectively reading one or more [variables](https://github.com/enlyze/enlyze-docs/blob/main/en/model/variables.md). There are two methods to register the available variables from a data source in the ENLYZE MDP, depending on the protocol used for the connection.

## **Variable Discovery**

Variable Discovery is an automated process where an Edge Device assigned to the data source queries the available variables and registers them in the ENLYZE MDP.

#### Applicable protocols:

* S7+ (OMS+)
* PVI
* OPC-DA
* OPC-UA
* Beckhoff ADS

## **Manual Registration**

If a data source is connected via a protocol that does not support Variable Discovery, the available variables must be registered manually. This often requires additional resources such as data sheets or project files.

#### Applicable protocols:

* S7 (Step 7)
* Modbus