Every annotation in ELAN belongs to a tier. You can change what tiers you use, but to do so, you have to understand how tiers work. Each tier shows as a separate row of annotations in the Timeline Viewer, and is available for display in the Grid, Text, and Subtitles Viewers. Within a tier, annotations do not overlap, but the annotations on one tier can overlap with annotations on other tiers. Every tier is classified as a particular Tier Type. The tier type determines Whether the tier uses a Controlled Vocabulary. A controlled vocabulary is a limited set of possible annotations that you can use in a tier. For example, a tier for eye gaze might use a controlled vocabulary consisting of annotations such as “left”, “center” and “right”; these would be the only possible values for annotations in this tier. If two or more tiers belong to the same tier type, they may still differ from each other in several ways. They might:
describe the behavior of different participants or different articulators of the same participant
have different parent tiers
use different default languages (English, Spanish, French, Chinese, etc.)
use different conventions or styles (formal vs. informal glossing, for example)
So, for example, you might have a tier type of “Free translation” and have two different tiers, one for a free translation in English and the other in Spanish. Or, you might have a tier type “handshape” with two different tiers, one for each hand. Or, you might have a tier type “Note” and different tiers for grammatical, ethnographic, and working notes. Thus, you have complete control over what tiers, tier types and controlled vocabularies you use to annotate a particular video, how the tiers depend on each other, and how the tiers are displayed. When you start work on a new video, it is helpful to base the annotation file on a template which contains a predefined set of tiers, tier types, and controlled vocabularies (see ). But, there is often reason to add new tiers or types, rearrange them, or make other changes. The following section explains how to do so.
You can control which tiers are displayed and in what order. There are two ways to rearrange the order in which tiers are displayed.
Right-click on the list of tiers and choose “Sort Tiers”, then choose which way you want them to be grouped.
“Sort by Hierarchy” displays relationships between parent and child tiers.
“Sort by tier Type” and “Sort by Participant” group them according to tier type and participant.
“Unsorted” leaves you completely free to rearrange the display as you want.
Click on the name of a tier and drag it up or down in the list. Depending on how you have chosen to group the tiers, there are limits to how you can rearrange them. For example, if you have chosen “Sort by Participant”, you can’t move a tier away from other tiers that have the same participant, but you can move that participant’s group of tiers up or down as a group.
To hide or display a tier, right-click in the list of tiers at the left edge of the, choose , and then either , , or choose which tiers to display with the check boxes.
If a tier has children, and you have chosen to sort the tiers by hierarchy, you can show or hide its children as a group. Right-click on the name of the parent tier, and choose.