On QlikView Help you can find a specific section for Field Tags:
"There are three different types of system tags, script generated system tags that cannot be altered by the user, script generated system tags that can be altered in the script and system tags that are set interactively by the user. System tags are always preceded by a $ sign.
The following system tags are automatically generated at the end of script generation. These cannot be changed by the user:
$system - denotes a system field.
$key - denotes a key field.
$keypart - denotes that the field is part of one or more synthetic keys.
$synthetic - denotes a synthetic key.
The following tags are also automatically generated at the end of script generation, but may be altered or overridden using script syntax, see Tag Field and Untag Field.
$hidden - denotes a hidden field.
$numeric - all (non-null) values in the field are numeric.
$integer - all (non-null) values in the field are integers.
$text - no values in the field are numeric.
$ascii - field values contain only standard ascii characters.
$date - all (non-null) values in the field can be interpreted as dates (integers).
$timestamp - all (non-null) values in the field can be interpreted as time stamps.
The following tags are set in the Document Properties: Tables dialog. They can be enabled and disabled by the user:
$dimension - denotes a field recommended for use in chart dimensions, list boxes, etc.
$measure - denotes a field recommended for use in expressions.
The user can also add custom tags. These are added either in the script using Script Syntax or in the Document Properties: Tables dialog. These custom tags may not use the same name as any system tag.
Note!
If the same tags are manipulated in both the script and in Document Properties: Tables the settings in the script will prevail.
In the QlikView help file you can find all details for generating field tags.
See the "Field tag" section.
"Tag Field
Provides a way of assigning tags to a field. Field names not present in the document are ignored. If conflicting occurrences of a field or tag name are found, the last value is used.
A field tagged with dimension will be displayed at the top of all field selection controls in QlikView except in the Edit Expression dialog.
A field tagged with measure will be displayed at the top of all field selection controls in the Edit Expression dialog.
The keyword can be used to add tags to a field using the syntax:
tag fields fieldlist using mapname
fieldlist is a comma separated list of the fields that should be tagged from this point in the script.
mapname is the name of a mapping table previously read in a Mapping load or Mapping select statement.
To set individual tags, the following syntax is used:
tag field fieldname with tagname
fieldname is the name of the field that should be tagged.
tagname is the name of the tag that should be applied to the field.
