An association is defined as a data attribute of the HTML tag. Instead of passing the reference to another control you define the ID of another control.
Caution:
Deprecated as of UI5 version 1.120, replaced by XML View.
The following code gives an example:
<div data-sap-ui-type="sap.m.Label" data-text="Message:" data-label-for="message"></div>
<div data-sap-ui-type="sap.m.Input" id="message"></div>
The code snippet defines the link between Label and Input by using the ID of Input as a value for the data-label-for attribute of the Label.