Brighi, R.

Lesmo, Leonardo

Mazzei, Alessandro

Palmirani, M.

Radicioni, Daniele Paolo

English

Radicioni, DANIELE PAOLO

Institutional Research Information System University of Turin

Towards Semantic Interpretationof Legal Modificationsthrough Deep Syntactic AnalysisRaffaella BRIGHI a, Leonardo LESMO b Alessandro MAZZEI b,Monica PALMIRANI a and Daniele P. RADICIONI b,aUniversità di Bologna, CIRSFIDbUniversità di Torino, Dipartimento di InformaticaAbstract. We are concerned with the automatic semantic interpretation of legalmodificatory provisions. We propose a novel approach which pairs deep syntacticparsing and a fine-grained taxonomy of legal modifications. Although still in adevelopmental stage, the implemented system can be used to annotate with meta-information modificatory provisions of NormaInRete documents.Keywords. Legal documents semantics, natural language processing, automaticinformation extraction.IntroductionMany efforts have been made in the last few years for investigating two problems inthe analysis of legal texts: how to automatically identify structural portions of legal doc-uments as long as their mutual references [4,3]; and how to grasp semantic informa-tion [1,9,5,2]. Various national initiatives have established XML standards for describinglegal sources and documents, which have grown into projects aiming at integration andinteroperability across all legal domains.Since hand-made annotations are time-consuming and error-prone, tools for mod-eling and representing the structure and content of norms are needed. Such tools couldgreatly benefit from automatic approaches to extract both structural and semantic datafrom legal texts, conceivably generating XML output. In the Italian legal domain a regu-lar structure has been identified in legal provisions, thereby making possible to use a texteditor to mark up semi-automatically structural partitions and normative references. Ourpresent research is grounded on the NormeInRete standard (NIR), for the Italian LegalText.1In this paper we single out a subset of the required annotations, namely the annota-tion of modificatory provisions. Since a normative system can be thought of as a body ofnorms changing over time, when new norms are introduced, existing ones get changed orejected (see [8] for a theory of diachronic normative system). Thus, it will often happenthat one norm refers to other norms, either to find its own completion (through the con-1http://www.normeinrete.it/.<dsp:sostituzione>         <dsp:pos xlink:href="#art1-com4" />          <dsp:norma xlink:href="urn:nir:stato:legge:2005-12-28;262"> <dsp:pos xlink:href="#rif9"/></dsp:norma>           <dsp:novella><dsp:pos xlink:href="#mod16-vir2" /></dsp:novella>          <dsp:novellando><dsp:pos xlink:href="#mod16-vir1" /></dsp:novellando>  </dsp:sostituzione> <comma id="art1-com4">          <num>4.</num>          <corpo> All'<mod id="mod16"><rif id="rif9" xlink:href="urn:nir:stato:legge:2005-12-28;262#art40-com1">articolo 40, comma 1, della legge 28 dicembre 2005, n. 262</rif>, le parole: <virgolette tipo="parola" id="mod16-vir1">"sei mesi"</virgolette> sono sostituite dalle seguenti: <virgolette tipo="parola" id="mod16-vir2">"dodici mesi"</virgolette></mod>.</corpo> </comma>  Figure 1. A substitution provision with structural and semantic markup for the Italian sentence All’articolo40, comma 1, della legge 28 dicembre 2005, n. 262, le parole “sei mesi” sono sostituite dalle seguenti “dodicimesi” (At the article 40, comma 1 of the law December 28, 2005 number 262, the words “six monts” are to besubstituted by the following “twelve monts”).tent referred to) or to change these other norms text, purview, or term of enforceabilitythrough a modificatory clause embedded in the norm itself.Although the legal language is more controlled than ordinary language, track-ing modifications requires considering the deep syntactic structure of sentences (see,e.g., [7]). Moreover, it involves encoding prior knowledge on the sorts of possible mod-ifications, and of the manners such modifications can practically occur in the legal dis-course. Therefore, the problem of annotating modificatory provisions is still a –relevant–open problem.The system for the semantic interpretation presented here has the followingstrengths: it builds on a deep parsing approach (based on the Turin University Parser,TUP [6]) and takes advantage of a fine-grained taxonomy of modificatory provisions.Furthermore, based on the taxonomy of modificatory provisions, we devised some se-mantic frame for each type of modification (e.g., for deletion, substitution, etc.). Eachsemantic frame has associated its own legal semantic roles (slots) to be filled: we adopta modular rule-based approach for filling the slots associated to the appropriate semanticframes.1. A taxonomy for modificatory provisionsThe NormeInRete (NIR) standard includes a part dedicated to modifications. Figure 1illustrates how a non-qualified provision can be enriched with semantic metadata (inbold) by marking it up in XML through NormeInRete.Before any semantic annotations are added, the text is marked up with structuraldata as well as with normative references and “quotation mark” elements, i.e. pieces oftext referring to a passive norm (such as any additional or replacement text, along witha string indicating where this text belongs in the passive norm). Semantic annotation en-riches a text with the <mod> element, which delimits a modificatory clause and withthe metadata, that fully qualify the modification and its attributes according to one of thefollowing classes:Type 1. A change made to the norm text or form (an integration, replacement, deletion,relocation) or to the norm meaning (an interpretation or variation of meaning or a mod-ification of clauses);Type 2.A change made to the range of a norm (an extension of its subject matter or rangeof application or a provision stating a derogation to it);Type 3. A change made to the temporal parameters of the norm (the time of its entryinto force, and the time when it becomes applicable or effective);Type 4. A change made to the status of the norm within the legal system (a decree-lawthat is made into law, an international treaty that is transposed into domestic law);Type 5. A change made to the powers conferred under a norm within the legal system(e.g., a EU directive transposed into domestic law).This classification was compiled by working together the modificatory forms de-scribed in legal theory and legal informatics [10], on the one hand, and the schemasfunctional to the consolidation of normative texts, on the other one.In addition to carrying out a legal-theoretical analysis, we have also surveyed a largebody of norms (about 5000 documents) that legal practitioners have semantically anno-tated on the basis of the NIR format. Our specific purpose was to investigate the effectiveusage of legal-theoretical categories, the language used and composition rules. Further-more, thanks to the regularity of the language used in active modificatory provisions, wehave individuated and encoded some idioms that frequently recur in the texts analyzed.The common idioms that recur in the different modificatory provisions have been sortedinto different classes of modificatory language, and to each class we have associatedone or more legal classes. The standard locutions are often accompanied by other recur-rent elements that specify the relevant modificatory action: Date, Quoted text, Position,Condition. Such information is exploited by the semantic interpreter, introduced in nextSection.2. Annotating modificatory provisionsWe preliminarily retrieve the location of a modificatory provision within the document,and then simplify the input text by replacing text fragments with their correspondingidentifiers. For example, by applying this rewriting procedure to the sentence in Figure 1,we obtain the text “All’RIF9, le parole VIR1 sono sostituite dalleseguenti VIR2”, which will be processed by the syntactic parser.To annotate modifications with meta-information, we have devised a two-step pro-cess. We first perform a syntactic analysis of the retrieved provision; then we semanti-cally annotate the retrieved provision by using its syntactic structure and based on themodificatory provisions taxonomy introduced above.2.1. Syntactic Analysis of Modificatory ProvisionsThe TUP is a rule-based parser that returns the syntactic structure of sentences in thedependency format. Dependencies are binary relations (e.g. subject-relation) betweena dominant word (the head, e.g. the verb) and a dominated word (the dependent, e.g.the noun-subject). After the morphological analysis and the part of speech tagging theinput sentence undergoes three phases for hanling chunking, coordination and verbalsubcategorization [6]. Such a tree dependency representation is the basis for the finalstep of semantic interpretation.8 sostituite1 All'-A 3 , 4 le 7 sono 9 dalle-DA 12 .1.1 All'-IL2 RIF99.1 dalle-IL11 VIR210 seguentiRMOD SEPARATOR OBJ AUX SUBJ ENDPREP-ARGDET-ARGPREP-ARGDET-ARGADJC-RMOD5 parole6 VIR1DET-ARGNOUN-APPOSITIONFigure 2. Syntactic analysis of the sentence: All’RIF9, le parole VIR1 sono sostituite dalle seguenti VIR2 (Atthe RIF9, the words VIR1 are substituted by the following VIR2).2.2. Semantic Interpretation: Filling Semantic FramesThe semantic interpreter checks if the root of the syntactic tree is a verb belonging to themodificatory provisions taxonomy (Section 1). In this case we have a fundamental cuethat the sentence being analyzed contains a modificatory provision, and we retrieve thesemantic frame associated with the verb. Then the semantic interpreter first uses a set ofpattern matching rules on the syntactic tree to recover the relevant parts of the syntacticsubstructures (e.g., the text fragments references). It then matches these relevant partswith the slots of the semantic frame.Consider for example the sentence: All’RIF9, le parole VIR1 sono sostituite dalleseguenti VIR2 (At the RIF9, the words VIR1 are substituted by the following VIR2) andthe corresponding syntactic tree in Figure 2. The root node of the syntactic tree is theverb “sostituire” (substitute). As a consequence, the semantic frame associated to theverb class substitute is selected: since the semantic roles (i.e. the slots of the frame) arerelated with the legal category substitution, the verbs substitute, change,modify, etc. havethe same frame. Three pattern matching rules match the syntactic tree in Figure 2; eachrule recovers a relevant part to fill a slot in the semantic frame associated to the verb“sostituire”. The first rule fills the semantic role referenceDocument with the string“RIF9”. This rule is activated by the conditions that i) the syntactic relation connecting“All’ ” to the verb is RMOD (that is, modification relation); and ii) that there is a descen-dent of the preposition which is a reference (RIF9). The second rule fills the semanticrole modifiedText with the string “VIR1”. This rule is activated by the conditions i)that the syntactic relation connecting “il” to the verb is OBJ (object relation); and ii) thatthere is a descendent of the preposition which is a reference (VIR1). The third rule fillsthe semantic role modifyingText with the string “VIR2”. This rule is activated by theconditions that i) the syntactic relation connecting “dalle” to the verb is SUBJ (subjectrelation); and ii) that there is a descendent of the preposition which is a reference (VIR2).No further rules can be applied to the structure, and the semantic interpretation algorithmreturns the following semantic frame.FRAME sostituirelegalCategory:           substitutionreferenceDocument:  RIF9modifiedText:             VIR1modifyingText:           VIR2Some further rules are designed to account for more complex linguistic constructions.For instance, in the case of coordination we need a number of special rules to duplicatethe information of the frame.3. Conclusions and Future WorksIn this paper we have presented a novel approach for the automatic annotation of modifi-catory provisions. We use a deep parser for Italian, and we adopt a rule-based algorithmin order to fill the semantic roles of the semantic frame associated with the modificatoryprovision. Our approach has some similarities with a number of previous works [2,1,7].The work in [2] is different from our system in that it only uses shallow syntactic analysisfor annotating general provisions; the work in [1] encodes the meaning of modificatoryprovisions with semantic frames, but it is related to the automatic generation of modifi-catory provisions rather than with their analysis; finally, the work described in [7] uses adeep syntactic parser but it aims at a full semantic interpretation of judicial opinions.Our system is still in a prototypal stage; in the next future we will enlarge the set ofrules in order to have a wider coverage of syntactic phenomena. Moreover, we plan toperform quantitative evaluation of the system by using a “gold standard” approach, i.e.testing against set of hand-annotated modificatory provisions to quantify the number ofcorrect annotations produced by the system.References[1] T. Arnold-Moore. Automatic generation of amendment legislation. In Procs. of ICAIL, pages 56–62,1997.[2] C. Biagioli, E. Francesconi, A. Passerini, S. Montemagni, and C. Soria. Automatic semantics extractionin law documents. In Procs. of ICAIL 2005, pages 133–140, New York, NY, USA, 2005. ACM.[3] C. Biagioli, E. Francesconi, P. Spinosa, and M. Taddei. The NIR project: Standards and tools for leg-islative drafting and legal document web publication. In Procs. of ICAIL Workshop on e-Government,pages 69–78, 2003.[4] A. Bolioli, L. Dini, P. Mercatali, and F. Romano. For the Automated Mark-up of Italian LegislativeTexts in XML. In T. Bench-Capon, A. Daskalopulu, and R. Winkels, editors, Procs. of Jurix 2002. IOSPress, 2002.[5] E. de Maat and R. Winkels. Categorisation of norms. In A. R. Lodder and L. Mommers, editors, Jurix2007: The Twentieth Annual Conference Annual Conference, pages 79–88. IOS Press, 2007.[6] L. Lesmo and V. Lombardo. Transformed Subcategorization Frames in Chunk Parsing. In Proc. 3rd Int.Conf. on Language Resources and Evaluation (LREC 2002), pages 512–519, Las Palmas, 2002.[7] L. T. McCarty. Deep semantic interpretations of legal texts. In Procs. of ICAIL 2007, pages 217–224,New York, NY, USA, 2007. ACM.[8] M. Palmirani and R. Brighi. Time model for managing the dynamic of normative system. ElectronicGovernment, pages 207–218, 2006.[9] J. Saias and P. Quaresma. A Methodology to Create Legal Ontologies in a Logic Programming BasedWeb Information Retrieval System. Artificial Intelligence and Law, 12(4):397–417, 2004.[10] G. Sartor. Il procedimento normativo regionale, chapter Riferimenti normativi e dinamica dei nessinormativi. Cedam, 1996.

Towards Semantic Interpretation of Legal Modifications through Deep Syntactic Analysis

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Towards Semantic Interpretation of Legal Modifications through Deep Syntactic Analysis

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