A Data filter is a way of prefiltering a Layer's records and if the map is later shared then its viewers will not be aware that a filter has been applied to the underlying Mapsimise Datasource.  

The currently active Data filter can be reviewed from the “Data Filter” option of the Layer’s context menu, clicking this option will launch the Data filter construction window.

The Data filter window selection lets the user turn off any applied Data filters, select from any that have already been defined or a new Data filter can be created.

A Data filter is made from a combination of field equations which can be constructed from a Layer’s record field, a selected operator, and a value. Each of these equations can be combined to create a single query that will be applied to the records returned by the Layer.

Rows can be added to the Data filter with the "Insert Row" button.  The first dropdown will allow the user to select from the Layer's field, the second dropdown will contain all of the operators and the third a value, both the operator and value are populated depending on the selected fields datatype.

Once multiple rows have been created, they can be grouped using the inclusive “And” options or the exclusive “Or” options. Multiple rows can be selected by clicking the arrow at the start of the row and once selected they can be grouped by selecting the relevant grouping button from the menu.

To change a grouping of a field the group can be selected and the "Ungroup" button can be clicked.

Once the Data filter is constructed it can be given a name and saved.

The newly created Data filter will be automatically applied to the Layer, but it can be deselected by reopening the Data filter window and selecting "No Data filter".