# Basic Activities

Basic activities are represented on the drawing canvas as rounded rectangles containing an icon and the user-defined name of the activity. The Actions section of the Palette contains all of the basic activities. For example: Assign, Invoke and Receive.

Most basic activities will require some additional configuration.

##### Start and End

Every BPEL process has implicit Start and End activities. These do not correspond to actual BPEL elements however, and are simply placeholders for visualizing the beginning and end of the process flow.

##### Assign

Assign activity

The Assign activity allows you to manipulate variables and message contents that are defined in the process.

##### Invoke

Invoke activity

The Invoke activity is used to send a message to an external service (one-way invocation), and optionally wait for a response (request and response). An Invoke can also define a compensation handler and a fault handler to handle exception conditions.

##### Receive

Receive activity

The Receive activity will wait for a specific message type from a service client.

##### Reply

Reply activity

The Reply activity is used to respond to clients with a specific message type, or fault message (if defined for the process interface).

##### Validate

Validate Input activity

The Validate activity is used to validate the values of variables against their XML Schema and WSDL data definitions. This includes the variable's data type as well as structure. If validation fails, the BPEL standard fault invalidVariables is thrown.

Validation is typically performed just before sending messages to a partner or client, or after receiving a message to ensure the message contains all required data and that the data is as expected.

##### Wait

Wait activity

A Wait activity will delay process execution for a certain amount of time, or until a given date and time; this is typically used to invoke an operation at a certain time. For example to update process state hourly or daily, or to collect some information from another service at a certain time of day.