The Practice Grammar

Assuming that you've already used Choose Grammar... to select the grammar practice.gr as the current grammar, and that you've used New under the File menu to open a palette and workspace, you're now ready to build.

1. The tools palette contains 4 areas. The first area contains the arrow tool and the scissors tool. Basically, keep the arrow tool highlighted when you're building trees, and select the scissors when you're pulling them apart. The second area contains a series of categories: S, V, N, P etc. When you click on one of these boxes (try it), different sets of words and other expressions appear in the third area, which contains lexical items and other phrase-structure rules. When you click on lexical items, different tree fragments appear in the fourth area of the palette. These are the pieces that you use to build phrase structure trees.

In the example below the verb category is highlighted, and the verb "sat" is highlighted, bringing up a tree fragment corresponding to an intransitive verb, i.e. with no position for an object for the verb.

2. Now we're going to run through the steps required to build a tree for the sentence the cat sat on the mat.

Click in the tree fragment area of the palette and use the mouse to drag the tree fragment into the workspace.

3. Next find the tree fragments associated with the other lexical items in the sentence, and drag these into the workspace.

4. Now you are ready to start combining tree fragments to create larger trees. A useful feature of Trees is that it will only let you combine tree fragments in ways that are allowed by the grammar you have chosen. To move a tree fragment around select its highest node, and drag with the mouse. Try doing this with a tree fragment for the lexical item "the". Try dragging the "Det" node over the "Det" node of the "cat" tree fragment. You should see that the "Det" node becomes highlighted. If you release the mouse now, the two tree fragments will be automatically combined.

Complete the two NPs, and then combine the NP "the mat" with the preposition "on" to create a series of larger tree fragments like the following. Notice that there's now no way to combine your tree fragments any further - you're going to need some more structure.

5. To combine the subject with the verb, select the tree fragment associated with "np-vp" from the S category, and drag it into the workspace. Use this tree fragment to combine the subject NP and the VP. At this point, though, you still can't integrate the PP into the tree.

6. In order to add the PP, which is a modifier of VP in this case, you first need to use the scissors tool to disconnect the VP node that you just attached below the S. Highlight the scissors tool and then click on the VP node with the tip of the scissors icon. The VP tree fragment will separate from the tree. [The scissors cannot be used on just any node - try clicking on the V node: nothing happens. This is because the grammar practice.gr has been programmed to only allow you to detach pieces at the point where they were attached.]

7. To create an attachment site for both the VP and the PP, choose the tree fragment corresponding to "vp-mod" from the palette and drag it into the workspace.

8. Now it should be straightforward to attach the VP-modifier structure below the S-node, and then to attach the VP and the PP below that. Now we're done with "the cat sat on the mat".

8. Next you should try to modify your existing tree to build a tree for the sentence "the cat saw the dog on the mat", this time interpreting the PP "on the mat" as a modifier of the NP, and not as a modifier of the VP (i.e. it's the dog that's on the mat, not the seeing event).

First use the scissors tool to detach the PP, the lower VP node and the VP-modifier tree fragment. You won't be needing the VP-modifier fragment or the "see" fragment for the new tree, so you can delete them by highlighting the top node of each fragment and selecting Clear from the Edit menu.

9. Now try to use other tree fragments that the grammar provides to create this structure...

10. Finally, modify the structure you built under (9) to create the structure below. [Tip: look for a tree fragment for building NP-modifiers under the N category list.]