We present here an intelligent man-machine interface which will be integrated to social robots dedicated to the elderly. Firstly, we discuss the specificities of conversational agents, also called chatbots, by comparing them to the other man-machine interfaces. Then, we establish how linguistic intelligence contributes to the development of high quality conversational agents. We finish by explaining the functioning of a conversational agent based on a linguistic processing of non-structured information. We are witnessing the advent of robots in our society, as Issac Asimov the writer of science fiction predicted in the 50s [1]. If the existing robots are way behind to be considered as well performing as the ones in the science fiction literature, huge and remarkable progresses have been made in the field of robotics in the last few years, especially robots functioning as caregivers 'social robots'. One of the characteristics of these robots is the integration of a system of verbal interactions between men and machines. Hence, this article highlights the characteristic of man-machine verbal interactions. The senior market in rich countries is striking due to the increase rate of aging of the population which is linked to the growth of life expectancy. The need to accompany this phenomenon by practices, so called, aging well is a huge stake for these societies. As seniors advance in age, the question of losing their autonomy raises. The projections show an increasing gap between the non-autonomous people and the professionals who help them overcome their difficulties. Therefore, robots are presented as a sustainable solution to compensate the lack of staff [2]. Robots, which give people a helpful hand, are characterized by their aspect, mobility and their communicative capacity. The first characteristic is the aspect which is more or less humanoid. Besides NADINE, a social robot which resembles exactly to its designer Nadia Thalman, other robots have a general shape which is similar to the human body. It is just their sizes which look more like an infant than an adult, for example, the robots PEPPER, NAO and ROMEO of SoftBanks Robotics Company. Some robots have a more sophisticated shape which bears little resemblance to the human body; such as, the ELLI-Q Company robots. Sometimes, their upper part looks like a human head, for example, the robots CUTTI or the robot KURI of Mayfield Robotics Company. There exists, also, robots which have the appearance of an animal, either totally as the seal robot PARO of Inno3Med company, or partially as the bear robot ROBEAR of Riken company. The second characteristic concerns the mobility or the absence of mobility of the robot. The most humanoid robots have a manner of movement which simulates human walking, for example, the version ZORA of NAO. Less humanoid robots use wheels to move,
for example the robots of Kompaï Company or the robot GIRAFF of GiraffPlus consortium. Other robots have mobile elements but they do not move, for example the robots ORIGIBOT of Origin Robotics Company. The third characteristic is the man-machine interaction. It can be focused on the non-verbal communication (tactile, auditory or kinesic), in order to create emotions for users with cognitive difficulties, which is the case with the therapeutic robot PARO. The use of a screen integrated in the robot is another possibility, for example the range of robots of Padbot Company. The interaction with a screen may be tactile or vocal. At last, robots allow the verbal interactions through answering questions and obeying orders. Thus, the version ZORA of NAO interacts with its users through conversations.
Robots, which give a helpful hand to old individuals, have many functions which mobilize specific technologies. The function of care is the oldest one. It consists of measuring the physiological state of a person by pressing on objects connected to a platform dedicated to medical supervision. When the signals detect abnormalities, an alert is launched. Another function is the prevention of individuals’ falls. It is applicable to robots which can be called smart walkers. They help people with balance troubles to move without risks. Developed computer systems manage the movements of these robots on the basis of the users’ indications and information about the spatial environment obtained from sensors. Another function of robots is the detection of falls. They, also focus on the geo-location of sensors. They inform a system which measures the position of the user and launches an alert when this position is out of the security norms. Tele-presence is a broader function. On the one hand, it allows watching after a senior from a distance by moving the robot in the senior’s environment and launching an alert in case of a problem. On the other hand, it communicates with the users. It involves a screen, which uses the videoconference and a system of remote control from a distance to move the screen mount. The function of sociability can be the fruit of tele-presence since it includes interactions between the user and another person. More broadly, the function of sociability concerns the companion robots, which are developed to compensate the emotional and social isolation of elderly. The function of helpfulness is consubstantial with robots since they perform tasks they were designed for. The last two functions, among others, focus on the technologies of chatbot type when it comes to verbal interactions. The quality of the chatbot is a crucial factor for the functions to work effectively.
For now, we are discussing only about chatbots. After placing the conversational agents1 at the man-machine interface, we precise the contribution of linguistic intelligence to the development of an elaborated chatbot, then we explain how a conversational agent, based on a linguistic processing of a non-structured information, functions. 2
Digital technologies process the human language with its written and oral forms. These digital technologies either interpret it or automatically reproduce it. They are dedicated either exclusively to the first part of processing, for example the analysis of emotions, or specifically to the second part, for example automated journalism, or to both parts simultaneously. Digital technologies dedicated to the simultaneous processing of both parts are regularly man-machine interfaces known as ‘chatbot’ or ‘conversational agents’. Chatbot, which is a compound English word, consists of the word chat and robot. A chatbot is presented in the form of an API which takes, as input, a sound or a text file and produces, as output, a sound or text file. This is followed by means of communication with the machine either in writing or speaking. The chatbot functions through the understanding of a message sent by a human being, a request, and through the formulation of another message, linked to the initial one, by the machine, a response.
Forms, interactive menus, command prompts, etc. allow the user to give instructions to a computer. Such modes of communication are, sometimes, insufficient to meet the user’s exact needs due to their rigid relativity. 1The terms conversational agent and chatbot are synonyms. The man-machine dialogue is conceived as a means to deal with these inadequacies. It consists of a system that allows an interaction, which is less or more narrow, between a human and a system. Its implementation is difficult because of the complexity of the language.
Therefore, the man-machine dialogue is a man-machine interface type as the language is a means to exchange
the data. The word dialogue2 indicates “ different shapes of interviews between two persons [
When the restrictions on use are striking, the verbal interactions have a big knowledge gap, as the GUS system
that is dedicated to online air ticket sales [
Communication systems in natural language of the first generation are fundamentally dedicated to database
queries or to very specific tasks. They permit to formulate instructions in natural language and answer them in
natural language. Interaction systems in natural language of the second generation are more developed. They can
deal with linguistic phenomena that impede the system effectiveness. To detect the human speaker’s intention, it
is necessary, in particular, to deal with the inference, the reference and the meta-dialogue. The processing of the
implicit meaning consists of highlighting the implicit consequences of a statement [
There are many types of chatbots. We can subdivide them into two categories [
Whatever the solutions, they can integrate technologies namely, on the one hand, speech-to-text, and, on the other hand, speech synthesis. In the first case, it is about converting automatically an oral message into a written one. In the second case, it is the contrary; a written message is automatically converted into an oral one. These two technological aspects are not presented here. The solution types 1 to 4, generally, correspond to a questionand-answer system, namely a question is asked by a human being and the answer is given by a machine. Type 5 solutions are considered to be more than a question-and-answer system, since it is about producing deeper verbal interactions between two human beings as one is a human being and the other is a machine.
Type 1 solutions are trivial because they are based on the preparation of ready sentences that correspond to
requests which, once recognized, are associated with beforehand recorded answers. The first chatbots designed
on this principle date from about fifty years ago [
Linguistic Intelligence Contribution3 By definition, an intelligent chatbot automatically understands the incoming messages (a question) and it associates them automatically to outgoing messages (a response). It aims at simulating verbal interactions between two humans by replacing one of the speakers (typically, the one who gives answers). The chatbot performance depends on its ability to interpret the incoming messages and produce relevant informative outgoing messages. In addition, its performance is, also, conditioned by the speed of exchanging information between the user and the machine.
In order to improve the performance of a chatbot, it has to include the linguistic processing of incoming and
outgoing messages. The processing of the incoming messages differs from the one of the outgoing messages since
in the first case, it relies on natural language understanding of texts and in the second case, it relies on the natural
language generation; that is to say two different technologies of natural language processing [
In order to facilitate the flow exchange in the information processing set, there has to be a formal and common
representation of the language data. Here, the propositional contents presentation of incoming and outgoing
messages is used, in terms of predicate-argument structure to understand and generate messages in a homogeneous
manner. The predicate-argument structure concept relies on Zellig S. Harris works [
In this theory, the concept of predicate is defined as a relationship in which the propositions, in its logical term, are analyzed as a link between entities, named arguments. This modeling differs from the Aristotelian modeling and gives place to the functional representation of the propositional content4: proposition => prédicat (argumenti).5 6
Applied to language facts, the calculation of predicates leads to associate the contents of an utterance to predicate-argument structure. For example, the utterance Le médecin soigne un patient (The doctor treats a patient) is metalinguistically represented by the following predicate-argument structure: soigner (médecin,patient)7. Utterances are distinguished by the fact of having simple or complex propositional content. In the second case, nested predicates characterize the utterances. For example, in the utterance Le médecin affirme au patient qu’il est guéri, (The doctor tells the patient that he is cured) the propositional content integrates another propositional content. Hence, the utterance is represented metalinguistically by a predicate-argument structure mentioning a predicate nested in another predicate: affirmer(médecin,patient, guéri(patient)).8
A more sophisticated abstraction layer is also possible by replacing lemmatized forms of lexical units by their semantic class. Thus, both of the utterances above have the following metalinguistic representation: SOIN(HUMAIN1,HUMAIN2) AFFIRMATION(HUMAIN1,HUMAIN2,GUERISON (HUMAIN2)).9
To process the information of the incoming and outgoing messages, the choice of linguistic formalism is
crucial. Thus, it is necessary to precise the type of the theoretical approach which underlies it. Theories about
language are distinguished by their privileged subject of study. Therefore, to study the language facts, morphological
theories have as an entry point the morphology, for example the theory named construction morphology [
The effectiveness of a chatbot is based on the understanding of the incoming message and its adequacy with the outgoing message. From this point of view, the predicate-argument structures contribute to the association of an incoming message and an outgoing message in the chain of processing information by allowing the connection between the outcome of the interpretation of the incoming message and the beginning of the production of the outgoing message. The solution presented here is based on natural language understanding technology and a natural language generation technology, cf. infra. The junction point between these two technologies is the arrival 4 The representation is namely functional because the predicate corresponds to an algebraic function, the argument is a variable. 5 The letter i indicates the number of arguments in relation to a predicate, namely arity. 6 Proposition => predicate (argumenti) 7 To treat (doctor, patient) 8 To tell (doctor, patient, cure (patient)). 9 TREATMENT(HUMAN1,HUMAN2).
TELL(HUMAN1,HUMAN2, HEALING(HUMAN2)). point of the first technology in the form of predicate-argument structure and the departure point of the second technology, also, in the form of predicate-argument structure. When the incoming message expresses a need, its metalinguistic representation is incomplete, namely one of its components is missing. The need expressed initially is satisfied in the outgoing message when the metalinguistic representation, which produces it, is saturated, namely the missing component of the other presentation is specified. The other elements of the two metalinguistic representations being similar are linked in a way that an association exists between the incoming message and the outgoing message. From this point of view, the predicate-argument structures are adapted, as metalinguistic representations, in order to make an association between the incoming message and the outgoing message.
The data model used to develop a chatbot grants an important role to the concepts of predicate and argument and to the relationship between them to automatically analyze language facts. The latter uses linguistic resources which correspond to local grammars, dictionaries and basic rules, cf. infra. The homogenization of the integration and the use of these resources in the system, which makes the conversational agent functions, creates the first constraint for the flow of information processing. Especially as, the processes of understanding and generating messages have opposite objectives. In the first case, the input is a text and the output is a metalinguistic representation. It is the opposite in the second case. The input is a metalinguistic representation and the output is a text. Moreover, it is necessary to associate the output of the natural language understanding to the input of the natural language generation. A human being conversation simulation represents a second constraint. From this point of view, the quality and relevance of the outgoing message is essential as well as the rapidity of the processing; the time of reply has to be about a second. Finally, the third constraint concerns the robustness of the system and its capacity to adapt to all kinds of computer science environment.
The chatbot relevance rate has been the subject of a quantitative and qualitative evaluation through the
evaluation of two system components: on the one hand, the one which processes the understanding of the incoming
messages, on the other hand, the one which is in charge of the outgoing messages. In both evaluations, we have
to measure the noise, non-relevant information presented by the system as relevant, and silence, relevant
information not selected by the system [
The second evaluation consists of checking if the results given by the solutions are in accordance or not with the expressed needs11. The evaluation protocol requires a person who doesn’t know the given results by the chatbot in order for the comparison to be independent. In addition, the evaluation consists of manually develop an outgoing messages corpus and compare it with incoming messages produced by the chatbot. It appears that 11% of the manually obtained data are missing, but only 4% of the automatically given data are not in the reference corpus. The failures of the automatic generation module are due to questions of synonymy which appears inadequately processed until now. 10 It is useful to suggest the following formulations to calculate them: Precision=true positive/true positive+false positive/Recall=true positive+false negative. The terms ‘true positive’ and ‘false negative’ indicate respectively the non-relevant information but identified as relevant and the relevant information but not identified as it is. 11 The second evaluation differs from the first one because the generation process does not match with the beforehand manually made tag process. The control over the data, that the natural generation method involves, confirms that the noise concept has no point in the evaluation. 4
A P I
Speech to Text
Linguistic resources
NLU (CAT)
NLG (GAT) Speech Synthesis
Knowledge base
Database
API (Application Programming Interface) is the interface which permits the interactions between men and
machines. Speech-to-text and speech synthesis modules have a role of transforming sound files into text files and
another text file into a sound file. The Natural Language Understanding (NLU) module includes a semantic
analysis engine which uses linguistic resources in the form of electronic dictionaries and local grammars [
The symbolic representation used in the system are metalinguistic representations, more precisely, it concerns semantic representations by making linguistic functioning mode of utterances. Incoming messages processed by the conversational agent have information requests or action requests. Information requests are introduced either in the form of questions (for example, Que mangeons nous ce soir? (What do we eat this evening?)) or in the form of requests (for example, Je voudrais savoir ce que nous mangeons ce soir (I would like to know what we eat this evening.)). Action requests are formulated in the form of orders (Monte le chauffage (turn up the heating)) or observations (J’ai froid (I am cold)). In the case of orders, the request is often formulated explicitly. In the case of observations, the request is implicit in a way that there has to be an inference in the observation about the need to be satisfied. Replies to action requests have two dimensions: extra-linguistic dimension, it concerns a concrete reply to the request in an appropriate way; and a linguistic dimension, it has to be known that the action requested is executed or about to be executed. Here, the extra-linguistic dimension is not developed.
When dealing with information or action requests, their metalinguistic representations include predicate-argument structures, cf. supra, in order to homogenize the process of information. Incoming messages are different in terms of the request type. In information requests, the human speaker’s intention expresses an informative need which has to be satisfied. Also, the metalinguistic representation of an incoming message, henceforth RMi (RMe) has to specify this need in a way that can be associated with a metalinguistic representation of an outgoing message, henceforth RMo (RMs), relying on the fact that this representation can satisfy its need. Metalinguistic representations expressed, in terms of predicate-argument structures as functional representations, correspond to the following formula according to if the predicate is: a monadic predicate (prédicat monadique), namely it takes only one argument, a unary operator (RM1 = PREDICAT (ARGUMENT1))12; a dyadic predicate (prédicat dyadique), namely it takes two arguments, binary operator (RM2 = PREDICAT (ARGUMENT1, ARGUMENT2))13; a triadic predicate (prédicat triadique), namely it takes three arguments, ternary operator (RM3 = PREDICAT (ARGUMENT1, ARGUMENT2, ARGUMENT3))14
The hypothesis has been made on the basis of the RMi which consists of merely one unknown element, a variable or a function, which is associated with the RMo from their other common elements which suggest the unknown element. Hence, the information request Qu’est-ce qu’il a comme repas? (What do you have for lunch?) has the following RMi MENU (X) and it is associated with the RMo MENU(%liste_plat%)15 which is associated with the RMo MENU (%liste_plat%) because the predicate MENU appears in both representations in a way that the argument %liste_plat% is the object of the question represented by X. It is the same case with the information request Est-ce que mon fils m’a appelé? (Did my son call me?), it has the following RMi OUI_NON=X (TELEPHONE (FILS (INTERLOCUTEURh) , INTERLOCUTEURh)16 and it is associated, according to the context, to either the RMo OUI (TELEPHONE(FILS(INTERLOCUTEURh), INTERLOCUTEURh))17or to the RMo NON(TELEPHONE (FILS (INTERLOCUTEURh), INTERLOCUTEURh))18 because (TELEPHONE (FILS (INTERLOCUTEURh), INTERLOCUTEURh))19 appears in both of the representations in a way that the predicate OUI (yes) or NON (no) is the object of the question represented by the predicate OUI_NON=X .
In action requests, the human speaker’s intention corresponds to a concrete need that has to be satisfied. An incoming message in a form of an order is sufficiently explicit to be returned to a RMi. However, when it is in a form of an observation, its intention is indirectly accessible to the interlocutor; there must be an inference of the semantic contents to express other semantic contents. The latter has to be added to the RMi in a form of a predicate-argument structure to the predicate-argument structure which has a link with the first semantic contents. There are inferences’ rules used to result in such RMi. The association of these representations to the RMo is different from the previous one. It concerns the identification, among the second ones, of similar predicate-argument structures with the first ones and concatenates them with a predicate structure to execute the initially formulated request. For example, the action request Il fait sombre? (Is it dark?) has the following RMi FAIBLE LUMINOSITE (DEIXIS) & ORDRE (INTERLOCUTEURh, INTERLOCUTEURr, ALLUMAGE (LUMIERE)) and it is associated with the RMo FAIBLE LUMINOSITE(DEIXIS) & ORDRE (INTERLOCUTEURh, INTERLOCUTEURr, ALLUMAGE (INTERLOCUTEURr, LUMIERE)) & INFORMATION (INTERLOCUTEURr, INTERLOCUTEURh, EXCECUTION ORDRE (INTERLOCUTEURh,INTERLOCUTEURr,ALLUMAGE (INTERLOCUTEURr , LUMIERE))).20The results RMo, for example to the following utterance is: Comme il fait sombre, vous souhaitez que j’allume la lumière. C’est fait (Because it is dark, you want me to turn on the lights. It is done).
The expressive language of semantic contents, an intention, comes from a huge diversity at the morphological,
syntactical and lexical levels [
The transformation of a RMo into an outgoing message is another difficulty. The choice has been made from a process which relies on conceptual dictionaries, namely dictionaries whose macrostructure is formed of concepts and the microstructure of lexical units associated with each concept. There are two conceptual dictionaries: the one of predicates and the one of arguments. The RMo are in form of predicate-argument structures as the predicate corresponds to the function and the arguments correspond to its variables. The predicates and their arguments are symbolized by their semantic class. Though the pragmatic adjustments, for example Lundi (Monday) when the incoming message is Quel jour sommes-nous? (What day are we?), the semantic class is related to the lexical units which they characterize. For example, the semantic class METEO_NEIGE21 characterizes the verb neiger (to snow), the noun neige (snow) and the adjective neigeux (snowy). The lexicon instances of a predicate, unlike the ones of arguments, have the particularity of being characterized by standard constructions. For example, the construction X0:PRONOM V22 characterizes the verbal predicate neiger (to snow) (il neige) (it snows), the constructions X0:PRONOM y avoir DU N and X0:GROUPE_NOMINAL être à LE N23 characterize the nominal predicate neige (il y a de la neige et le temps est à la neige) (snow) (there is snow and weather forecast calls for snow)) and the construction X0:PRONOM+GROUPE_NOMINAL être A24 characterize the adjective predicate neigeux (snowy). The unique argument, namely X0, is semantically specified at the distributional semantic level; it is the subject in all the constructions as deictic, nominal group or both of them. There are reconstructions associated with constructions, namely non-standard constructions or the component order is modified in a way that the syntactic modification does not involve the major semantic modification. For example, the construction X0:GROUPE_NOMINAL être à LE N25 (Le temps est à la neige) (weather forecast calls for snow) has as a possible reconstruction, ce être à LE N que être X0:GROUPE_NOMNAL26 (C’est à la neige qu’est le temps) (it is called for snow by weather forecast). The juxtaposition of these different metainformation gives rise to sentence patterns in the instantiation phase of the lexical units in the constructions, namely when the major components are replaced by a beforehand specified vocabulary. Morphosyntactic resources are, then, used to apply formal grammar to sentence patterns and produce well-formed utterances. Linguistic descriptions are formalized in electronic dictionaries and rule bases. Their good quality and systemicity are fundamental for the well-functioning of the Natural Language Generation module. The latter simulates the human language by suggesting all kinds of utterances relevant to the same semantic contents. The objective is met because the lexical and syntactic variety is taken into consideration by the data model implemented by the system.
In the Natural Language Understanding module, the incoming messages are enhanced with semantic tags, dictionaries and local grammars. Below, we introduce an excerpt of one of these dictionaries, the body-parts dictionary. This dictionary contributes to the identification and qualification of information relevant to the health of the conversational agent users.
annulaire,.N+H_PARTIE_CORPS (ring finger,. N+H_BODY_PART) annulaires,annulaire.N+H_PARTIE_CORPS (ring fingers,ring finger. N+H_BODY_PART) articulation,.N+H_PARTIE_CORPS (joint,. N+H_BODY_PART) articulations,articulation.N+H_PARTIE_CORPS (joints,joint. N+H_BODY_PART) avant bras,avant-bras.N+H_PARTIE_CORPS (forearms,forearm. N+H_BODY_PART) avant-bras,.N+H_PARTIE_CORPS (forearm,. N+H_BODY_PART) auriculaire,.N+H_PARTIE_CORPS (auricular,. N+H_BODY_PART) auriculaires,auriculaire .N+H_PARTIE_CORPS (auricular,auricular. N+H_BODY_PART) bouches,.N+H_PARTIE_CORPS (mouths,. N+H_BODY_PART)
The information on the left side of the full stop is of a linguistic nature and the one on the right side of the full stop is of a meta-linguistic nature. The macrostructure of the dictionary is made of lexical units constituting the dictionary. The microstructure is constituted of a lexical unit followed by a comma and its lemmatized form if the entry is an alternative. Next, there is a full stop which is mandatory followed by a grammatical category (N is the code for noun) and by meta-information of a semantic nature, in this case, the code H_PARTIE_CORPS (H_BODY_PART) is relative to body part hyperclass. This meta-information may be called from a local grammar in a way that all the dictionary items are recognized.
Below, we introduce one of these local grammars, the local grammar namely PROBLEME_SANTE (HEALTH_PROBLEM).
Local grammars are formal representations of contextual elements. Regular grammars used by a parser which
constitute the simplest grammar class in Chomsky hierarchy [
PROBLEME_SANTE (HEALTH_PROBLEM) graph calls other graphs and one of them is the PARTIE_CORPS (BODY_PART) graph which represents the dictionary PARTIE_CORPS. It allows the identification of all kinds of utterances which have a relationship with a health problem related to the human speaker, for example, J’ai mal à la poitrine or Mon ventre me fait mal (I have pain in my chest or My stomach hurts). It qualifies them, by adding a tag, in a predicate-argument structure form PROBLEME_SANTE (LOCUTEUR_HUMAIN)27.
The information specified in the utterance is not always explicit. For example, in the use of a chatbot context, reporting a physical pain implies the implicit information ‘j’ai besoin d’être soigné’ (‘I need to be treated’). It follows that the tag PROBLEME_SANTE (LOCUTEUR_HUMAIN) is interpreted as an action request and it has to be completed with the tag APPEL (LOCUTEUR_MACHINE,PERSONNEL_SOIGNANT)28. Such transformations happen when the RMo are given to the Natural Language Generation module and they are processed by inference rules.
In the Natural Language Generation module, the semantic representation of the outgoing message is a predicate-argument structure, cf. supra. From this representation, it is possible to generate a well formulated utterance by applying well ranked rules which consider: semantic properties of a distributional and lexical nature; syntactic properties related to the predicate constructions and the positioning of the lexical material, specified in a previous rule, in these constructions (a procedure named instanciation (instantiation)); enunciative properties relative to the actualization of predicates and arguments (a procedure named actualisation (actualization)); morphosyntactic 27 HEALTH_PROBLEM (HUMAN_SPEAKER). 28 CALL (MACHINE_SPEAKER, NURSING_STAFF). properties which give rise to verb conjugation and coordinating conjunction rules with adjectives and nouns; pragmatic properties which narrow the field of possibilities and take the extra-linguistic context into consideration.
The semantic, syntactic and enunciative properties are listed in a conceptual dictionary. This dictionary is transferred to the database. The fourth category of properties is about the morphosyntactic dictionary, created as part of the project. This second dictionary is also inserted in the database. The fifth category of properties is covered by the knowledge base.
These linguistic and extra-linguistic resources are used by the natural generation module through the implementation of a set of rules which use linguistic resources inserted in the database. Below, we list the different rules used. The order of their presentation corresponds to their order in the passages before.
Predicate identification rule
Semantic properties of a distributional nature define propositional contents as the predicates and their arguments which are specified in a functional representation form as a semantic value. For example, utterances such as Il y a du brouillard, C’est brouillardeux and Le temps est au brouillard (There is fog, It is foggy and The weather forecast calls for fog) share the same semantic contents represented as the following: METEO_BROUILLARD (DEIXIS+METEO)29. The first rule used by the natural generation module relies on this type of meta-linguistic description.
The departure point of the generation module is a predicate-argument structure. Its functional representation indicates if we are dealing with a simple predication or a complex predication. The second predication is distinguished from the first one by the fact that it incorporates at least another simple or complex predication, in its argument domain. The functional representation of a complex predication involves at least a double parenthesis, which allows its automatic identification. For example, the utterance Le médecin est absent (The doctor is absent) is analyzed as a simple predication which corresponds to the following predicate-argument structure: 1) (ABSENCE (HUMAIN:MEDECIN))30.
Furthermore, an utterance as: Le médecin a déclaré aux patients qu’il était absent (The doctor announced to his patients that he was absent) is analyzed as a complex predication which corresponds to the following predicate-argument structure: 2) (DECLARATION(HUMAIN:MEDECIN,HUMAIN:PATIENT,ABSENCE(HUMAIN:MEDECIN)))31.
The end of the representation 1) involves one closing parenthesis while the representation 2) involves two closing parentheses. The number of the closing parentheses indicates the type of the predication. If it is simple, it includes one closing parenthesis. If it is complex, it includes more than one closing parenthesis.
First, it is a question of the rules related to the simple predication.
Distributional rule
This rule specifies the information which considers the predicate-argument structure by explicitly specifying
the semantic nature of predicates and the different categories of arguments. There are three categories of
predicates, monadic predicates, dyadic predicates and the triadic predicates, cf. supra32. It follows that there are three
categories of arguments: the first argument which is coded X0 and it is observed with the three categories of
29 WEATHER REPORT_FOG (DEIXIS+WEATHER REPORT).
30 ABSENCE (HUMAN:DOCTOR).
31ANNOUNCEMENT(HUMAN:DOCTOR,HUMAN:PATIENT,ABSENCE(HUMAN:DOCTOR)))
32 There is a fourth category of predicates, a predicate that its domain of arguments is quaternary. Its scarcity led to its neglecting
[
The code %type_temps% means that the information is not in the linguistic database but depends on the knowledge base. For the X0 argument, it is about either a substantive of the METEO (WEATHER FORECAST) class or about a pronoun of the DEICTIQUE (DEICTIC) class. The exact nature of the deictic is specified at the level of the constructional rule (règle constructionnelle), cf. infra.
To limit the number of answers, the knowledge base is requested straightaway to identify a precised weather forecast type. As a result, the previous rule is rewritten as the following (in the case of a fine weather): PRED=BEAU_TEMPS(X0=METEO+X0=DEICTIQUE)34.
It is about the specification of the linguistic units associated with the semantic categories of predicates and arguments. For example, for the predicate class BEAU_TEMPS (FINE_WEATHER), the rule produces the following linguistic forms: the nouns beau temps, temps magnifique (fine weather, a nice day); the adjectives agréable, beau, bon, magnifique (pleasant, delightful, nice); or a verbal phrase aller vers le beau (it is going to be beautiful) and for the argumental class METEO (WEATHER FORECAST) the nouns météo and temps (weather forecast and weather).
Constructional rule
It is about the specification of the constructions connected to the linguistic forms of predicates. For example, in beau temps (fine weather), it is about the construction X0 :DEIXIS1 avoir DU N35 as N is for beau temps (fine weather)36, and the subject is the argument X0 of the nominal predicate under the value coded DEIXIS1, which means on or nous (we).
Reconstruction rule
The construction, associated with the linguistic form of a predicate, is canonical; it involves a standard layout
of the subject position and, if any, the positions of the first and second complement occupied by the arguments.
In speech, this layout may be changed and codified [
coffee, a toast and an orange juice) and with the reconstructions il y avoir comme N X0:GN38 (Il y a comme petit déjeuner du café, des tartines et un jus d’orange) (There is for breakfast: coffee, a toast and an orange juice), etc.
The lexical variety of the predicates and arguments and the constructional variety, combined with each other, explain that from the same propositional content, the system produces a huge number of utterances and allows the stimulation of a human conversation, cf. infra.
This rule consists of merging the three previous rules and inserting the linguistic forms in the positions of the predicates and arguments. For example, in the previous example, the construction LE N être X0: GN is transformed into LE petit déjeuner être DET café, DET tartines, DET jus d’orange39, the reconstruction il y avoir comme N X0:GN into il y avoir comme petit déjeuner DET café, DET tartines, DET jus d’orange 40, etc.
It is about the specification of the predicate time and the argument determination. For example, when the instantiation rule gives such results : aujourd’hui, DET météo être à la pluie/aujourd’hui, DET temps être à la pluie/DET météo être à la pluie aujourd’hui/DET temps être à la pluie aujourd’hui41. The application of the code relative to the enunciative properties of the nominal predicate pluie (rain) produces the result : aujourd’hui, LE météo être:PRESENT à la pluie/aujourd’hui, LE temps être:PRESENT à la pluie/LE météo être:PRESENT à la pluie aujourd’hui, LE temps être:PRESENT à la pluie aujourd’hui42.
This rule specifies in which conditions, there are contractions, transformations or removal of concatenated forms and stop words (mots vides), for example:
The role of this rule is to limit the descriptive power of the syntactic properties, particularly the ones which concern the reconstructions and/or the lexical combinatorics. In fact, all the predicate uses defined by the same construction do not accept the reconstructions associated with them. Hence, it is convenient to limit them by only specifying the ones applicable. For example, adjective predicates bon, mauvais, pourri (good, bad, rotten) are characterized by the construction X0: GN être A (X0: NG to be A). This allows the reconstruction X0: GN être 38There to be as N X0:NG 39THE breakfast to be DET coffee, DET toast, DET orange juice 40There to have as breakfast DET coffee, DET toast, DET orange juice 41Today, DET weather forecast to be at the rain/today, DET weather to be at the rain/DET weather forecast to be at the rain today/DET weather to be at the rain today 42 Today, THE weather forecast to be: PRESENT at the rain/today, THE weather to be: PRESENT at the rain/ THE weather forecast to be: PRESENT at the rain today, THE weather to be: PRESENT at the rain today. très A and X0:GN être vraiment A (X0: NG to be very A and X0 : NG to be really A) in a way that the following utterances can be generated: La météo est bonne, La météo est très bonne, La météo est vraiment bonne, Le temps est bon, Le temps est très bon, Le temps est vraiment bon, La météo est mauvaise, La météo est très mauvaise, La météo est vraiment mauvaise, Le temps est mauvais, Le temps est très mauvais, Le temps est vraiment mauvais, La météo est pourrie, La météo est très pourrie, La météo est vraiment pourrie, Le temps est pourri, Le temps est très pourri, Le temps est vraiment pourri. (The weather forecast is good, The weather forecast is very good, The weather forecast is really good, the weather is good, the weather is very good, the weather is really good, the weather forecast is bad, the weather forecast is very bad, the weather forecast is really bad, the weather forecast is rotten, the weather forecast is very rotten, the weather forecast is really rotten). Yet, the utterances Le temps est bon, Le temps est très bon, Le temps est vraiment bon (the weather is good, the weather is very good, the weather is really good) are not acceptable (lexical combinatorics constraint) and La météo est très pourrie (the weather forecast is rotten) (reconstruction constraint). In addition, it is convenient to precise these constraints in a lexico-syntactic adjustment rule.
In the case of a complex predication, the same rules are applied. However, once the rule of the predicate identification is applied, they have to process the embedded predicate before the predicate which embeds a unit. When there are more than two predicates which are embedded, those rules must be applied from the most embedded predicate to the one whose level of embedding is the highest, cf. supra. 5
The works that have been carried out as part of the chatbot development have contributed to set the foundations of a lexical generative grammar of the French language. The development of this grammar will allow the creation of other chatbot processing others themes.