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Features
Features are ezra's means of encoding the research-relevant properties of hits, and they are the main way for annotators to provide hits with content. A feature is a parameter which may take on a value (get "valued") for a given hit. Each feature is decorated with a descriptive question illustrating its meaning in the context of the research project.
Features are specified by principal investigators, who give their possible values and questions and associate them with targets. They are valued by annotators, who review hits and set them with the appropriate feature values.
A feature is defined by three properties: name, instructions, and type.
The feature's name is a string used to identify it system-wide. It must be unique: no two features can have the same name.
The feature's instructions are a string that serves to unpack the intended meaning of the feature. The instructions provide a reminder to annotators of what they will be looking for, as well as a guide to the interpretation of the finished dataset.
The type of the feature constrains the values that the feature may take on. There are three types of feature: Single, Multiple, and String. A feature of the Single type has a finite set of possible values, exactly one of which may be the feature's value for a particular hit. A Multiple feature also has a finite set of values, but a given hit may have zero or more values for the feature. A String feature, finally, may take on an arbitrary string as its value.
Hits can be valued for features by means of the annotation screen for the hit. The process of valuing features is described in detail in the annotator tutorial.
Features may be created and associated with targets by means of the Features page. To create a new feature and associate it with some targets, click the New feature button at the top of that page. This will take you to the feature creation page.
The feature creation page contains text boxes for the feature's name and instructions. To specify these properties of the feature, simply fill in each box. The type of the feature may be selected by means of the Feature Type menu to the right of the Name text box.
Features of the Single or Multiple type must have possible values. Values, which are simply strings, are specified by entering text into an Add value box beneath the Add value button on the right side of the interactive area. To create more boxes into which to enter text, click the Add value button to add more fields.
All targets in the ezra system are listed in the bottom right corner of the feature creation page's interactive area. Each feature has a check box to its left. To associate the new feature with a target, check the box to the left of the target's name.
Once you have set up the value's parameters to your satisfaction, click Create feature to add the feature to the system. This will take you to the feature's information page.
Besides giving you access to the feature creation page, the Features page contains a list of features present in the system. This list allows you to view each feature and edit its properties.
To view a feature, click its name in the Features page index. This will take you to the feature information page, which displays the feature's parameters. These include the feature's name, instructions, type, possible values, and associated targets. To return to the Features page index from this page, click Back.
From the feature information page, you are able to edit the feature itself, as well as editing the list of targets associated with the feature. To edit the feature, click the Edit link next to its name. To edit its list of targets, click the Edit button above its list of targets.
Features can be edited via links from both the Features page index and, as just explained, the feature information page. To edit a feature via the index, click the Edit link next to its name in the list. This will take you to the feature editing page, which is identical to the feature creation page except for having Save update in place of Create feature.