Projection
Projection is the mechanism by which, in a given syntactic tree, one or two constituents are integrated into a more complex structure. It is the bottom-up movement of merging or collapsing one or two subordinate nodes into a higher node in order to form a syntactic structure. In the UNLarium framework, projection is used to build the sentence structure out of the individual constituents (head, specifier, adjunct and complement) during natural language generation.
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Use
Projections are used to build trees out of the head-driven relations, i.e., to go from:
XS(head;specifier);, which describes the relation between the head of the structure and its specifier XA(head;adjunct);, which describes the relation between the head of the structure and its adjuncts XC(head;complement);, which describes the relation between the head of the structure and its complements XH(head);, which describes the head of the structure
to:
XP
/ \
spec XB
/ \
XB adjt
/ \
X comp
|
head
This is done by a set of rules as follows:
first intermediate projection (lower XB)
- XC(%head;%comp)
- =XB(%head;%comp);
- projects the first intermediate projection (XB) in case of comp
- XA(%head;%comp)
- =XB(%head;%adjt);
- projects the first intermediate projection (XB) in case of adjt (i.e., when there is no comp)
- XH(%head)
- =XB(%head;);
- projects the first intermediate projection (XB) when there is no comp or adjt (the second argument is empty)
second intermediate projection (if any)
- XB(%head;%xb1)XA(%head;%adjt)
- =XB(XB(%head;%xb1);%adjt));
- projects the second intermediate projection (XB) in case of adjt (the tree has a comp or a adjt, or two adjts)
- XB(%head;%comp1)XC(%head;%comp2)
- =XB(XB(%head;%comp1);%comp2));
- projects the second intermediate projection (XB) in case of comp (the tree has two comps)
third intermediate projection (if any)
- XB(XB(%head;%xb1);%xb2))XA(%head;%adjt)
- =XB(XB(XB(%head;%xb1);xb2);%adjt)); (the tree has one comp and two adjts, two comps and one adjt or three adjts)
fourth intermediate projection (if any)
...
maximal projection
- XB(%head;)
- =XP(XB(%head;););
- minimal tree: the tree has only the head (no comp, adjt or spec)
- B(%head;%xb)
- =XP(XB(%head;%xb););
- the tree has only one intermediate projection and no spec
- XB(%head;%xb)XS(%head;%spec)
- =XP(XB(%head;%xb);%spec);
- the tree has only one intermediate projection and the spec
- XB(%head;%xb)
- =XP(XB(%head;%xb););
- the tree has only one intermediate projection and no spec
- XB(XB(%head;%xb1);%xb2)XS(%head;%spec)
- =XP(XB(XB(%head;%xb1);%xb2);%spec);
- the tree has two intermediate projections and the spec
- XB(XB(%head;%xb1);%xb2)
- =XP(XB(XB(%head;%xb1);%xb2););
- the tree has two intermediate projections and no spec
etc.
Syntax
Projection rules are S-rules of the replace type, i.e.:
<RELATION> := <RELATION>;
Where <RELATION> is a syntactic relation, including a <HEAD>, in case of head-only relations (VH, NH, PH, JH, AH, CH, IH, DH), or a <HEAD> and a <ARGUMENT>, in case of binary relations (VC, VS, VA, NC, NS, NA, etc.).
There are mainly two types of projection rules:
- Replace, when the number of relations in the left side is the same as in the right side, and which is used for collapsing single-branched structures (i.e., parent nodes that have one single child)
- Merge, when the number of relations in the left side is greater than in the right side, and which is used for collapsing double-branched structures (i.e., parent nodes that have two children).
Examples
- VH(%head):=VB(%head);
- The head of the verbal phrase becomes the head of the verbal intermediate projection (VB)
- VC(%head;%comp):=VB(%head;%comp);
- The head of the verbal phrase becomes the head of the verbal intermediate projection and the complement of the verbal phrase becomes the second argument of the verbal intermediate projection
- VB(%head;%comp)VA(%head;%adjt):=VB(VB(%head;%comp);%adjt);
- The verbal intermediate projection becomes the head of a higher intermediate projection that takes the adjunct to the verb as second argument
