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<Paper uid="P84-1061">
  <Title>I SPECIFICATION OF THE I:~PUT STRUCTURES FOR INFE~ENC I\[IG</Title>
  <Section position="4" start_page="292" end_page="294" type="metho">
    <SectionTitle>
II INFERENCE TYPES
</SectionTitle>
    <Paragraph position="0"> A. \[q_eans of Implementation The inference rules are progranm~ed in 9-1anguage (Colmerauer, 1982), which provides rules that carry out transforr~at~ ions of oriented graphs. Since the structures accepted by the rules must not contain complex labels, every complex sy~bol labelling a no~e in WR's has the form of a whole subtree in the Q-language notation (in a &amp;quot;~-tree).</Paragraph>
    <Paragraph position="1"> The set of TR's constitutes a semantic network, in which the individu~l T!{'s are connected into a com\[~lex whole hy means of pointers between tl\]e occurrences of lexical units and the corresponding entries in the lexicon. (Ouestions of different objects of the same kind referred to in different TR's will be handled only in the future ex\]~eriments.) The following procedures eperate o~n  TI{ &amp;quot;s : (i\] the extraction of (possibly\] relevant pieces of information from the stock of kno,:?led~e ; (ii\] the application of inference rules on the relevant }?ieces of information, (iii) the retrieval of the answer(s).</Paragraph>
    <Paragraph position="2"> '\]:he extraction of the so-calleE rslevant .~J~c,~s of inforT~'.~tion is based on ~:atcbing the. ~&amp;quot;~.-. of the input question with  the lexicon and extracti~,~ khosC/: Y\[''&lt;~ that intersect with the Tq o~ the give,: question in at least one s~-.ecific 1 ..... ~c~_ v~lue (i.e. other than the&amp;quot;g~nerll %ztor, -~.,:. one, the copula, etc.\] ; the rezt cf the t r~es (s~\]~-~oscd to }:~. irreluvant for ~h.,liven questJ.~n) are th?.n d~let_~,}.. The set of i&amp;quot;.!:~,'~nt U'. &amp;quot;'-~ \[~{ c,-cr-ztmi U.:O~l k. V t\['~: rules o~ i~r-~r ~.&amp;quot;,.cc. r f \[, rui.? of in.fer~=r, Ce l..;z bee-\] ?.-~-li? ~, '::th i:h,.::  source TR as well as the derived TR constitute a part of the stock of knowledge a,,d a,, serve as source TR s for further processing. In order to avoid infinite cycles, the whole proced :r= oI inferencing is divided into several Q-systems (notice that rules within a single Q-system are applied s ~o,:g as the conditions for their application are fulfilled, i.e. there is no ordering of the rules ).</Paragraph>
    <Paragraph position="3">  E. Types of Inference Rules I. Rules operatin@ on a single TR: (i) the structure of the tree is preserved; the transformation concerns only (a) part(s) of the .o..p~ex symbol of some node of the CDS (i.e. label(s) of some node(s)in the Q-tree of the TR): (a) change of a grammateme:</Paragraph>
    <Paragraph position="5"> A0te:, In our highly simplified and schematic shapes of the rules we quote only thos~ labels of the nodes that are relevlnt for the rule in question; the sign == stands for &amp;quot;rewrite as&amp;quot;; Ndevice stands for any no~n ,,i%h the sem~,~tPSu f=ature of &amp;quot;device&amp;quot;, Vperfor m for a verb with the semantic feature of action vePSb=, ~ossib and II~dic denote the |raimnatemes of predicate modality. null E x.: An implifier can activate a Das,-ive network to form an active analogue.  == An amplifier activates a passive network to form an active anal~gue.</Paragraph>
    <Paragraph position="6"> (b) change of a functor (type of complementation): null</Paragraph>
    <Paragraph position="8"> E__{x.: Operational amplifier is used with negative feedback. == With operational a,uplifier negative feedback is used.</Paragraph>
    <Paragraph position="10"> al operations are performed by means of operational amplifiers.</Paragraph>
    <Paragraph position="11"> Note: Act, Pat, Instr, Accomp, Regard stand for the functors of Actor, Patient, Instrument, Accompaniment and Regard, respectively; D denotes a general participant, gen ~g~ change of the lexical part of the complex symbol accompanied by a change of some gramnlateme or functor:</Paragraph>
    <Paragraph position="13"> Ex.: With few hlgh-performance opera-~ional amplifiers it is possible to maintain a linear relationship betw- null een input and output without employing negative feedback.== Hith most &amp;i. it is necessary to maintain ...</Paragraph>
    <Paragraph position="14"> employing negative feedback.</Paragraph>
    <Paragraph position="15"> (ii) a whole subtree is replaced by another subtree: Ex.: a negative feedback == a negative feedback circuit (iii) extraction of a subtree to create an independent TR: - relative clause in the topic part of the TR</Paragraph>
    <Paragraph position="17"> Ex.: An operational amplifier, which a--~tivates a passive network to form an active analogue, is an unusually versatile device. == An operational amplifier activates a passive network to form an active analogue.</Paragraph>
    <Paragraph position="18"> Note: L stands for the grammateme &amp;quot;contextually bound&amp;quot;, R for &amp;quot;non-bound&amp;quot;, Gener for the functor of general relationship.</Paragraph>
    <Paragraph position="19"> - causal clause in TR's with affirmative modality Vi-Affirm (Vj-Cause (...))... == vj t...) EX.: Since an operational amplifier i-~ designed to perform mathematical operations, such basic operations as ... are performed readily. == An operational amplifier is designed to perform mathematical operations.</Paragraph>
    <Paragraph position="20"> - deletion of an attribute in the focus part of a TR</Paragraph>
    <Paragraph position="22"> E_~x.: Operational amplifiers are used as regulators ... to minimize loading of reference ~\]iod~ vermittlng full exploitation of the diode's precision temperature stability. == Operational amplifiers are used as regulators ... to minimize loading of reference diodes.</Paragraph>
    <Paragraph position="23"> (iv) the transformation gives rise to two TR s distributivity of conjunction and disjunction (under certain conditions: e.g. for the distributivity of disjunction to hold, the grammateme of Indic with the main verb is replaced by the grammateme of Possib) E x.: Operational amplifiers are used in active filter networks to provide gain and frequency selectivity. == Operatinal amplifiers are used in active filter networks to provide gain. Operational amplifiBrs are used in active networks to provide frequency selectivity.</Paragraph>
    <Paragraph position="24"> 2. Rules operatin 9 (simultaneously) on two TR s left-hand side of the rule refers to two TR's) - conjoining of TR's with the same Actor Ex.: An operational amplifier activates a passive network to form an active analogue. An operational amplifier performs mathematical operations. =~ An operational amplifier activates .... and performs .... use of definitions: the rule is triggered by the presence of an assertion of the form &amp;quot;X is called Y&amp;quot; and substitutes all occurrences of the lex~cal labels X in all TR's by the lexical label Y</Paragraph>
  </Section>
  <Section position="5" start_page="294" end_page="295" type="metho">
    <SectionTitle>
III EFFECTIVE LINKS BETWEEN INFERENCING
AND ANSWER RETRIEVAL
</SectionTitle>
    <Paragraph position="0"> A. The Retrieval Procedure Th~ retrieval of an answer in the enriched set of assertions (TR's) is performed in the following stepsl (a) first it is checked whether the lexical value of the root of the TR is identical with that of the TR of the question; if the question has the form &amp;quot;What is performed (done, carried out) by X?&amp;quot;, then the TR from the enriched set must include an action verb as a label of its root; (b) the path leading from the root to the wh-word is checked (yes-no questions are.</Paragraph>
    <Paragraph position="1"> excluded from the first stage of our experiments); the rightmost path in the relevant TR must coincide with the wh-path in its lexical labels, contextual--boundness, grammatemes and functors (with some possible deviations determined by conditions of substitutability: Singular - Plural, Manner - Accompaniment, etc.); the wh-word in the question must be matched by ~-lexical unit of the potential answer, where the latter may be further expanded; (c~ if also the rest of the two compared TR s meet the conditions of identity or substitutability, the relevant TR is marked as a full answer to the given question; if this is not the case but at least one of the nodes depending on a node included in the wh-path meets these conditions, then the relevant TR is marked as an indirect (partial) answer.</Paragraph>
    <Paragraph position="2"> B. Towards an Effective Application of Inference Rules In the course of the experiments it soon became clear that even with a very limited number of inference rules the memory space was rapidly exceeded. It was then necessary to find a way how to achieve an effective application of the inference rules and at the same time not to restrict the choice of relevant answers.</Paragraph>
    <Paragraph position="3"> Among other things, the following issues should be taken into consideration: The rules substituting subtrees for subtrees are used rather frequently, as well as those substituting only a label of one node (in the Q-tree, i.e. one element of the complex symbol in the CDS), preserving the overall structure of the tree untouched. These rules operate in both directions, so that it appears as useful to use in such cases a similar strategy as with synonymous expressions, i.e. to decide on a single representation both in the TR of the question and that included in the stock of knowledge; this would lead to an important decrease of the number of TR's that undergo further inference transformations.</Paragraph>
    <Paragraph position="4"> Only those TR's are selected for the final steps of the retrieval of the answer (see point (a) in III.A) that coincide with the TR of the question in the lexical label of the root, i.e. the main verb. If the inference rules are ordered in such a way that the rules changing an element of the label of the root are applied before the rest of the rules, then the first step of the retrieval procedure can be made before the application of other inference rules. This again leads to a con- null siderable reduction of the number of TR's on which the rest of the inference rules are applied; only such TR's are left in the stock of relevant TR's (i)that agree with the TR of the question in the label of the root (its ~exical label may belong to superordinated or subordinated lexioal values: device - amplifier, etc.), (ii) that i~clude the lexical label of the root oC the question in some other place than at the root of the relevant TR, (iii) if the question has the form &amp;quot;Which N &amp;quot; (i.e the wh-n~de depends on its * o- , o head in the relation of general relationship), then also those TR's are preserved that contain an identical N node (noun) on any level of the tree.</Paragraph>
    <Paragraph position="5"> The use of Q-language brings about one difficulty, namely that the rules have to be formulated for each level for the tree separately. It is possible to avoid this complication by a simple temporary rearrangement of the Q-tree, which results in a tree in which all nodes with lexical labels are on the same level; the rules for a substitution of the lexical labels can be then applied in one step, after which the tree is &amp;quot;returned&amp;quot; into its original shape.</Paragraph>
    <Paragraph position="6"> These and similar considerations have led us to the following ordering of the individual steps of the inference and retrieval procedure: I. application of rules transforming the input structure to such an extent that the lexlcal label of the root of the tree is not preserved in the tree of a potential answer;  2. a partial retrieval of the answer according to the root of the tree; 3. application of rules substituting other labels pertinent to the root of the tree; 4. partial retrieval of the answer according to the root of the tree; 5. application of inference rules operatinq on a single tree; 6. application of inference rules operating on two trees; 7. the steps (b) and (c) from the  retrieval of the answer (see III.A above).</Paragraph>
  </Section>
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