|Lesson 1A||Lesson 1B||Lesson 2X||Lesson 2A||Lesson 2B||Lesson 2C||Lesson 2D|
Read Document 2X
and Homework 2B.
The grammar eg2B builds upon eg2A, which in turn was formed from eg2X. Using eg2B, and the updated dictionary wd2B, it will be possible to parse sentences containing "wh- strings". These strings, with some exceptions, begin with a "wh- word" (what, who, which, etc.). Their distinguishing feature is that the portion following the wh word has the same structure as an <ASSERTION> except that one element that should have a non-null value is empty. We say the element is "omitted" though the linguistic analysis is that the "omitted" element has been made into a pronoun that is part of the wh- word (e.g. the ich of which). Thus, in the tower which () was built, the subject tower of was built has been "omitted", but can be said to be present in pronoun form in the word which. An example of an omitted object is the tower in the tower which the Vikings built (), and an example of an omitted prepositional object is the tower in the tower which they know of (). As the preceding examples illustrate, wh strings can occur as right adjuncts of a noun, so RN is expanded to include wh strings as options.
Some wh strings occur in <SUBJECT> or <OBJECT> position, e.g. what () was built as <SUBJECT> in What () was built was a tower, and as <OBJECT> in They discovered what () was built. The beginning grammar already had an instance of a wh- string, <NREP>. However, <NREP> was limited to the wh- word what and had no general mechanism for "omitted" elements. The grammar eg2B replaces NREP with strings (options of <SNWH>) based on the more general treatment of wh-strings. In eg2B, <SNWH> has options WHS-N, i.e.,a wh sentence missing a noun (which they built (), who () built it) and PWHS, a preposition followed by a wh- sentence with no omission of a required element (by whom it was built).
The definition of WHS-N consists of 'WHO', 'WHOM', 'THAT', 'WHICH', or 'WHAT' followed by <ASSERTION>. To allow for a <*NULL> in a noun position within the <ASSERTION>, the option <*NULLWH> is added in <SUBJECT> and <NSTGO>. The restrictions WWH1, WWH2, and WWH3 check that one and only one NULLWH is assigned within the omitting wh- string. Note that not all wh-words in WHS-N, as defined in this grammar, should be allowed in all positions of WHS-N occurrence (*the tower what was built). Further refinement of the grammar should deal with this problem.
WWH1 is housed in <SUBJECT>, applied after NULLWH is attached. It checks that NULLWH is within a WHS-N ($PATH1), checks that no previous acceptance of a NULLWH has occurred within WHS-N, signalled by assigning the node attribute DIDOMIT ($NO-PREV-OM), and then assigns the DIDOMIT node attribute ($ASSIGN). WWH2 is similar to WWH1; it accepts NULLWH within <OBJECT> or within a right adjunct <PN> in an <OBJECT> N (the people whom we know the language of ()). WWH3 checks that there is indeed a NULLWH in a WHS-N.
In eg2B, the definition of <SUBJECT> has been expanded to include <SN>, with options <THATS>, <TOVO>, <SNWH>. Examples of <THATS> and <TOVO> occurring in <SUBJECT> are: That a tower was built is known; To build a tower takes many years. In <OBJECT> position the options of <SN>, namely <SNWH>, <TOVO> and <THATS>, appear as individual options since not all verbs that occur with one of these object strings can occur with them all. Also <ASSERTION> has been added as an option of <OBJECT> e.g. the Vikings did it in They know the Vikings did it.
New options have been added to <OBJECT> for strings that include the adverbial particle DP. DP words are often also prepositions (e.g. up) but unlike prepositions DPs can occur either before or after their coelement noun or string. E.g., DP = out in They found out the facts, They found the facts out, They found out who built it. Because these particles may appear before or after an NSTGO and before an <SN>, there are three DP object strings: <DP2> (find out the facts), <DP3> (find the facts out), and <DPSN> (find out who built it). A fourth possibility, a particle after <SN>, does not occur (*find who built it out.)
Each verb that can occur with a DP object occurs only with a specified few DPs, listed as values of the attribute DPVAL, which is assigned to the DP object strings on the OBJLIST attribute of that verb. The new restriction WOBJDP checks that the particular DP (e.g. out) in an occurring DP object string (e.g. <DP2> = [find] 'out the facts) of a verb (e.g. find) appears as a value of the attribute DPVAL of DP2 on the OBJLIST attribute in the dictionary entry for that verb. Thus, WOBJDP will succeed for find it out and fail (or produce an unintended parse) for find it in because in is not a value of the attribute DPVAL of DP2 on the OBJLIST attribute of find.
Some verbs (e.g. tower in The Vikings tower over the investigators) occur with <PN> as their object (over the investigators in the previous example). Again, as with DP object strings, each verb that can occur with a PN object must have the particular prepostion(s) specified. For this, an attribute PVAL is defined, similar in form and function to the attribute DPVAL described above. The new restriction WOBJPN is similar to WOBJDP. It will succeed for The Vikings tower over the investigators and fail for The Vikings tower under the investigators.
Note that four new routines, IMMEDIATE-NODE, IMMEDIATE-STRING, NONSEG-IMMSTG, and PRESENT-ELEMENT have been added to the grammar and are used in restrictons.
The dictionary wd2B also has new elements. SNWH, DP2, DP3, and DPSN appear as values of OBJLIST in some dictionary entries, and the attribute DPVAL is new. The only word in the text which occurs as a DP, out, was given that classification in addition to P. The words in and up were added as other instances of both P and DP. To enable the restriction WOBJDP to check for the occurrence of the particular DP specified by the DPVAL attribute of the verb's DP object, each DP word in the dictionary is assigned an attribute consisting of its "name". Thus, the DP category of out in wd2B.txt has the form: DP: ('OUT').
Again, the situation of an object string beginning with P is similar to that of an object string beginning with a DP. To enable the restriction WOBJPN to check for the occurrence of the particular P specified by the PVAL attribute of the verb's PN object, each P word in the dictionary is assigned an attribute consisting of its "name". Thus, the P category of over in wd2B.txt has the form: P: ('OVER').
CHANGES MADE IN THE GRAMMAR
CHANGES MADE IN THE DICTIONARY