Patent Application: US-36718703-A

Abstract:
the invention relates to a method for generating natural language in computer - based dialog systems . this method uses — in contrast to known declarative approaches — a highly controllable procedural approach , comprising the following steps : 1 : generating an input tree from an input file which comprises a sequence of simple semantic representation language statements ; 2 : inserting elementary syntactic information into the tree ; 3 : applying elementary operations such as sub - tree insertion and manipulation ; 4 : accessing lexical and / or language specific information ; 5 : generating syntactic structures oriented towards normalised interface structures from the structured deep syntactic input tree ; 6 : realizing and expanding structure types by inserting and / or transforming of pre - defined structures , inserting determiners and ordering sub - structures . 7 : generating morphologic transformations ; 8 : optionally , carrying out final refinements , comprising phonetic refinement , pretty print and / or cleaning operations of the tree and the node decorations ; 9 : outputting a graphic and / or textual representation of the final tree structure .

Description:
the invention addresses the task of dynamic natural language generation in a conversational system . it allows for the combination of both speedy and high - quality output of text realisation . in addition to use in dialog systems , the present invention could be used for other real - time applications ( e . g . natural language interfaces to databases ). some parts of the present invention ( ssrl ) could be used for other tasks of linguistic knowledge representation ( such as text summarisation ). the invention consists in a specific method that has been developed to enable a natural language generation system for real - time applications . this method comprises a sequence of steps . in the preferred embodiment of the invention , these steps are realized by a set of tools , comprising comprendium kernel 5 . 0 developed at sail labs munich , which interprets the lisp - like so - called lingware programming language ; the simple semantic - pragmatic representation language ( ssrl ); a generation - directed knowledge representation language ( gdkrl ); and a dictionary - free flexing algorithm for morphological generation . an embodiment of the invention is explained in detail below . reference is made to the attached drawings , wherein fig1 and 2 are charts depicting the various components of the method according to the invention and the interaction among these components , and fig3 to 15 are charts depicting the various generation steps of the present invention . in the proposed system , the tactical generation starts from semantic - pragmatic representations which consist of a set of statements ( predicates and meta predicates ) containing semantic , syntactic , pragmatic and morphological information that constitutes the content of the text to be generated . the elements of the representations are so - called simple semantic representation language ( ssrl ) expressions . the ssrl language describes event and entity nodes of a network , their properties , and links among them . an example illustrating the ssrl input that would ultimately generate the sentence “ your order consists of an extra large pizza with cheese , artichokes , peppers and ham , a medium bottle of coca - cola and a dessert with cream ” is given below in example ( 1 ). the ssrl representations are created by a text planning process ( the strategic component generating the what ) which determines the content and ( abstract ) structure of an utterance . ssrl representations serve as an interface between strategic and tactical generation . the tactical generation uses the programming environment of the comprendium kernel 5 . 0 by sail labs munich , which interprets the lingware programming language that the generation grammar is written in . lingware is based on a set of lisp and lisp - like functions , that is , built - in functions on the basis of lisp , which represent linguistic operators for natural language processing . it has been used in the context of machine translation for analysis , transfer and generation grammars at sail labs . it is being used for the first time to write generation grammars for conversational systems . in what follows , program parts of the generation grammar are called ( lingware -) procedures . each expression of the representation language has a corresponding lingware procedure with the same name . thus , the names of the ssrl expressions simultaneously represent representation language units and program parts of the tactical generator . the sequences of ssrl statements are prompted by actions which are initiated or specified by the application ( e . g . a dialog manager ). specific ssrl statements in turn are triggered by calling the corresponding homonymous procedures . the tactical natural language text generation consists in creating deep and surface tree descriptions as well as morphologically well - formed sequences of text units . the tree structures are generated in different steps by well defined sequences of lingware procedures which represent the implemented linguistic grammar . a dictionary - free flexing algorithm (‘ flexer ’) is applied for morphological generation . this component is also integrated into the tactical component . the resulting text output — sentence is : “ your order consists of an extra large pizza with cheese , artichokes , peppers and ham , a medium bottle of coca - cola and a dessert with cream .” the procedural rules of the proposed system use feature structures and unification of feature structures to determine the applicability of both phrase structure rules and feature instantiations . the tactical generation proceeds from an initial tree structure and the ssrl representation which reflects the semantic , pragmatic and lexical content of an utterance . the initial tree is defined as a normalised double branching structure with a root ( named s as a symbol for sentence ) and two ( text -) limiting sons , symbolised by $, as depicted below : the respective ssrl representation is generated by a preceding ( strategic ) component which either is part of an application ( e . g . for database question / answer applications where a direct answer has to be given based on the database search results ), or an intermediate component between the application and the tactical generation , such as within conversational systems . in this latter framework , a dialog management component pre - defines and plans the extension of system utterances and sends them to the text modelling component , which in turn supplements the elementary information provided by the dialog manager and determines the final sequence of ssrl statements . this sequence constitutes the basis for the tactical generation . the different ssrl statements in terms of meaningful units of the representation correspond to functions and program parts of the text generator . these functions initiate the generation process . the names of the representation units and the lingware functions are identical : an ssrl statement as part of the representation at the same time represents a specific part of the generation lingware which is called up by a procedure bearing a name which is identical to that of the ssrl statement . for instance , an ssrl statement ( action x1 “ start ”) calls the lingware procedure ( action x1 “ start ”), where action is the name of the called sub - program and x1 and “ start ” are the arguments of the procedure . this action procedure makes sure that a node is inserted into the tree structure and puts pointers , features and values onto the node in compliance with its parameters — here , the pointer ev - id x1 and the notion “ start ”. lingware procedures matching the ssrl statements perform the first step of the generation process : they insert new nodes into a flat tree structure and assign additional information to the nodes . thus , the first step of the tactical generation consists in creating a basic tree structure with decorated nodes corresponding to the current ssrl representation . if the complete sequence of ssrl statements is exhausted , that is , if all respective lingware procedures are called and executed , a flat semantic - pragmatic tree which represents the utterance to be realised has been generated . the nodes of the tree possess elementary feature value pairs . they consist of linguistic functions and relational indicators . further procedures are called on the subsequent generation layers in a well defined order . they build the structural description by starting from the deep semantic - pragmatic tree up to creating a surface - structure tree . a separate morphologic generation component is called in order to generate morphologically well - formed surface strings for the output of the generation . to sum up , during the generation process , the realiser generates flat deep structures from semantic - pragmatic expressions , then syntactic deep structures from the deep semantic - pragmatic structures and from these syntactic deep structures surface strings . with a view to the internal process , the following steps can be distinguished : the first part converts semantic - pragmatic expressions into a flat deep tree structure and is totally language independent the second part converts the semantic - pragmatic tree into a deep syntactic tree , which still is language independent the third part converts the deep , language independent syntactic structure into a language dependent surface structure and a well - formed text sequence of inflected words . thus , the most important and general type of operation performed by the text generation is to convert or transform tree structures . for this purpose the following technology is employed : the definition of elementary and specific lingware procedures which insert sub - trees into already generated trees or modify them ( this method is comparable to the procedure of tree adjoining grammars ( so - called tags ) ( cf . joshi 1987 )) transformations are defined by context conditions which are composed by structure descriptions and node decorations . an overview of the various components with respect to dynamic generation and the interaction among these components is depicted in fig1 and 2 . the initial generation call g which has as parameter a series of ssrl statements calls the procedure generate which has as parameter the ssrl input file . the procedure generate reads the current ssrl - sequence representation and calls up xfm , an ( lingware ) operator with two arguments , namely description of the input tree structure and transformed output structure ), which creates the initial tree structure and / or resets former result trees . after creating the initial tree , generate calls up step by step the procedures described below which carry out the generation . ssrl input file for generating the sentence : “ the phone number is used to identify your records in our files .” in order to complete the initial input tree ( s →$ $) each statement of the respective ssrl - sequence representation is evaluated . the result of this evaluation is a flat semantic - pragmatic tree . the evaluation itself is performed by the function evals , which has as parameter the sequence of ssrl statements . three procedures , put - syn - func , insert - syn - cat , aux - insert , insert elementary syntactic information into the tree structure and onto the tree nodes . these procedures have no parameters . a flow chart of insertion of syntactic categories is depicted in fig6 after evaluating the deep input tree , elementary operations such as sub - tree insertion and manipulation ( for instance , identification of coordinations , attributes and relations ) are applied . the respective procedures are : logicizer , attributor and relator . they do not have parameters . identification of logical connections and attributes is depicted in fig7 the identified relations are depicted in fig8 . after evaluating the notions / concepts supplied by the strategic component , notions / concepts are replaced by canonical forms via access to the lexicon . the lexicon access allows the application of multilingual facilities . the respective functions that perform lexicon access are get - prep - can and get - lex - info . they do not have parameters . [ 0160 ] fig9 shows the lexicon lookup , particularly insertion of canonical forms ( base lexemes ). generation level 5 : evaluation of the structured deep syntactic input tree this level generates syntactic structures ( oriented towards normalised interface structures ) and takes care of gapping phenomena and insertions as language specific parts as well as the ordering of cls sub - structures . the respective functions are : internal - cls - structure , insert - specific - structure , del - ident - phrase , and cls - order . these functions do not have parameters . syntactic restructuring is depicted in fig1 , clausal word - ordering is shown in fig1 . this level takes care of the insertion and / or transformation of pre - defined structures , determiner insertion as well as ordering of np and ap sub - structures . the respective functions are struct - expansion , det - insert , np - order , and ap - order . they do not have parameters . the expanded syntactic structure can be seen in fig1 . phrasal ordering and determiner insertion is shown in fig1 . at this level , the call to the morphological generation component (‘ flexer tool ’) is performed . the respective function get - inflected - form does not have parameters . the results can be seen in fig1 . at this level , phonetic refinement , pretty print and cleaning operations of the tree and the node decorations are carried out . the respective functions corr - onset , mult - coord and clean - nodes do not have parameters . this level provides a graphic representation of the final tree structure and output of the text string . the respective functions draw and allostr do not take any parameters . the resulting tree structure after pretty print and cleaning operations are shown in fig1 . busemann , s . 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