A Grammar and a Lexicon for a Text-Production System

In a text-produqtion system high and special demands are placed on the grammar and the lexicon. This paper will view these comDonents in such a system (overview in section 1). First, the subcomponente dealing with semantic information and with syntactic information will be presented se!:arataly (section 2). The probtems of relating these two types of information are then identified (section 3). Finally, strategies designed to meet the problems are proDose¢l and discussed (section 4). One of the issues that will be illustrated is what happens when a systemic linguistic approach is combined with a Kt..ONE like knowledge representation • a novel and hitherto unexplored combination] 1. THE PLACE OF A G R A M M A R AND A LEXICON IN PENMAN This gaper will view a grammar and a lexicon as integral parts of a text production system (PENMAN). This perspective leads to certain recluirements on the form of the grammar and that of the eubparts of the lexicon and on the strategies for integrating these components with each other and with other parts of the system. In the course of the I~resentstion of the componentS, the subcomDonents and the integrating strategies, these requirements will be addressed. Here I will give a brief overview of the system. PENMAN is a successor tO KDS ([12], [14] and [13]) and is being created to produce muiti.sentential natural English text, It has as some of its componentS a knowledge domain, encoded in a KL.ONE like representation, a reader model, a text-planner, a lexicon, end a Sentence generator (called NIGEL). The grammar used in NIGEL is a Systemic Grammar of English of the type develol:~d by Michael Halliday • see below for references. For present DurOoses the grammar, the lexic,n and their environment can be represented as shown in Figure 1. The lines enclose setS; the boxes are the linguistic compenents. The dotted lines represent parts that have been develoDed independently of the I~'esent project, but which are being implemented, refined and revised, and the continuous lines represent components whose design ill being developed within the project. The box labeled syntax stands for syntactic information, both of the general kind that iS needed to generate structures (the grammar;, the left part of the box) and of the more Sl~=cific kind that is needed for the syntactic definition of lexical items (the syntactic subentry of lexical items; to the right in the box -the term lexicogrammar can also be uasd to denote both ends of the box). 1Thitl reBe•rcti web SUOl~fled by the Air Force Office of Scientific Re~lllrrJ1 contract NO. F49620-7~-¢-01St, The view~ and ¢OIX:IuIIonI contained in this document Me thoe~ of the author and ~ou ld not be intemretKI u neceB~mly ~ t J ~ ~ official goli¢iee or e~clors~mcm=, either e ; ~ o r e ~ or im~isd. Of the Air FOrCAI Office of . ~ W I O R ~ r c h ot the U.S. Government. The reeea¢ch r e ~ t ~ • joint effort end so ao t t~ =tm~ming from it whicti are the sub, tahoe Of this m l ~ ' . I would like to thank in p~rt~cull=r WIIIklm MInn, who tieb helped i1~ think, given n~e ~ h ~ l ideaa s u g g ~ o ~ l and commented extensively on dr.Jft= of th@ PaDre3, without him it ~ not be. I am ~ gretefu| tO Yeeutomo Fukumochi for he~p(ul commcmUI On I dran end to Michael Hldlldey, who h ~ mecle clear to m@ rmmy sylRemz¢ i:~n¢iOl~ end In=Ught~ N•turelly, ] am eolefy reso¢~i~le for errors in the grelMmtetlon and contenL ' CONCEPTUALS J~ :::::::::::::::::::::::::::::::::::::::::::::::: i s¥ N T jiiiiii iiiii!iiliii!ii i Grammor ~i::i::i::il Lexls ii::~i!i!ilil I .................................. ] L ~iiii::i::iiiii~ii!iii~::~:::.::i~ii~ii~:.:::.:::.i:.i~ General Specif ic