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Next: Conclusions Up: RST-Tool: An RST Analysis Previous: Text Segmentation

Text Structuring

The second step of RST Analysis involves structuring the text. The text structuring interface of the RST-Tool allows the user to connect the segments into a rhetorical structure tree, as shown in figure 3. For presentation, the RST-Tool follows the graphical style presented in Mann & Thompson (1987).

  
Figure 3: Text Structuring Tool

Initially, all segments are unconnected, ordered at the top of the window. The user can then drag the mouse from one segment (the nucleus) to another (the satellite). Upon releasing the mouse button, the system offers a menu of relations to choose from (the user can use the relation-sets provided with the system, or provide their own).

The user can switch freely between text segmentation and text structuring mode -- to edit text, or to change segment boundaries. The system keeps track of the structure assigned so far. If the user, in editing the text, deletes a segment, the system forgets structuring information concerning that segment.

Types of Structure

Apart from simple nuclear-satellite relations, the tool allows a number of other options:

  
Figure 4: Scoping and Multi-nuclear Relations

  
Figure 5: Constituent Structure

Defining Relations

When forming a relation between two text-nodes, a menu pops up prompting the user to specify the relation-type. These relations are not built into the system, but can be edited by the user. The user modifies a text file to add, delete or modify the relation set. A sample set derived from Mann & Thompson (1987) is included with the distribution.

Other Points

Because rst-structures can become very elaborate, the RST Tool allows the user to collapse sub-trees -- hiding the substructure under a node, This makes it easier, for instance, to connect two nodes which normally would not appear on the same page of the editor.

The user can save the present state of the screen as postscript, for inclusion in Latex documents. Alternatively, a snapshot utility can be used to save selected parts of the structure in other formats. The structured text can be saved to a file, for later re-editing, or for use in variable-length document presentation.



next up previous
Next: Conclusions Up: RST-Tool: An RST Analysis Previous: Text Segmentation



Mick O'Donnell
Wed Mar 12 16:46:17 GMT 1997