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A probabilistic approach to language structure. Annarita Felici and Paul Pal Royal Holloway, University of London Helsinki 2-4 June 2008 A.Felici@rhul.ac.ukP.Pal@rhul.ac.uk. Outline. Field of investigation Research goals Data Probabilistic analysis Information Theory Entropy results.

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A probabilistic approach to language structure

Annarita Felici and Paul Pal

Royal Holloway, University of London

Helsinki 2-4 June 2008



  • Field of investigation

  • Research goals

  • Data

  • Probabilistic analysis

  • Information Theory

  • Entropy results


Field of investigation

  • Repetitive language structure in multilingual legal text

  • EU normative statements in translation

  • Languages of investigation

    • English, French, German and Italian


Field of investigation: legal norms

  • Deontic norms (from the Greek deon = duty).

     obligations, prohibitions, permissions and authorizations

  • Constitutive performatives

     The uttering of a performative is, or is part of, the doing of a certain kind of action or speech acts (Austin 1962)

    Uttering a sentence = doing things


Other norm types

  • Logical necessity

     necessary requirements or competences

  • Non-binding norms

     guidelines, correct procedure


Research goals

  • To evaluate the degree of prescriptive standardization in French, German and Italian with reference to English

  • To predict translation equivalents in French, German and Italian


under the conditions that:

  • English legal drafting is highly standardized

  • The EU and the main English drafting suggest modal verbs for prescriptive norms (Coode 1843, Driedger 1976, Dickerson 1975, Thornton 1996)

  • Text types under investigation are repetitive and reusable

  • Text types under investigation can be more or less binding



Multilingual parallel corpus

  • Origin:EU

  • Corpus size:1.404.723 words

  • Text type:normative

  • Type of docs:Secondary Legislation(Regulations,Decisions,Directives, Recommendations)

  • Years:2001-04

  • Languages:English, French, German, Italian


Probabilistic Analysis

Information Theory

To measure the amount of linguistic alternatives when translating a repetitive normative statement from English into French, German and Italian

= Quantifying information by reducing uncertainty

  • more alternatives = more uncertainty (high entropy)

  • less alternatives = more standardization, certainty (low entropy)


Probabilistic Variables

  • Categories of expressions

  • Linguistic forms

     English modals Entry point for parallel retrieval

    shall, must, may, can, should


Categories of expression

  • Constitutive norms and performatives

  • Logical necessity

  • Permissions and authorizations

  • Capability

  • Non-binding norms


Linguistic forms

  • Indicative (pres.)

  • Modal verbs (mv)

  • Verbal periphrasis (vp)

  • Lexicalized modal expressions (le)

  • Ellipses (0- correspondence)


Linguistic formsLinguistic equivalents used in constitutive and performative norms


Linguistic formsLinguistic equivalents used to convey permissions and authorizations


  • Given the English system of modality, which is the relative probability of choosing an equivalent modal verb in the translation of may or must and a different linguistic form as the equivalent of shall?

  • Is the probability of a choice in a system affected by a choice in another?


Information Theory

  • the information value or content h(p) is dependent on the probability of occurrence (p) of an event (Shannon 1949)

    h(p)= - log (p) = log (1/p)

    Entropy degree of uncertainty

    (= shortage of information due to the large number of alternatives)


Probabilistic analysis

  • The frequency of occurrence (ni) of each linguistic form is associated with a category

  • A probability variable (pi) is derived from the estimated proportion of a particular linguistic form


Probabilistic analysis

  • In English

    P1 = p mv→ shall = n shall/ n;p2 = pmv → must = nmust/ n;

    p3 = pmv →should = nshould/n; p4 =pmv → can = ncan/n;

    p5 = pmv → may = nmay/ n

  • In French, German and Italian

    p1 = pindicative + pmv + pvp + pme + pellipses;

    p2 = pindicative + pmv + pvp + pme + pellipses

    and so on.


Linguistic forms and frequencies of occurrences in the EU Regulation for the selected categories of 1) constitutive norms and 2) permissions and authorization


Probabilistic approach

  • The sum of these probabilities produces different information values

  • The expected information content of a system is the sum of the information contents weighted by the probabilities for each possible outcome


Entropy : extrema

  • Variations in the language-specific p(i) values of linguistic forms produce distribution profiles reflecting the characteristics of the corresponding language.

  • Mathematically it can be shown that

    If all the p(i) values are equal (equi-probable situation), the profile is a uniform distribution and results in maximum entropy.

    If only one probability p(i) is maximum and the remaining p(i) values are zero, the entropy is minimum (e.g. English).

    All other distributions lie between these two limits (e.g. French, German and Italian)


A concrete example

  • Regulation document in English, French, German and Italian + a fictitious language.

  • One category of expression: e.g. the constitutive norms.

  • 5 linguistic forms for this category.

  • Total number of modal verbs and alternatives: 2075.


Constitutive norm

Frequency of occurrences of expression modes in 4 real languages and one fictitious language


Histogram of 5 modes of expression


Comparison based on Entropy

Computed Entropy of Constitutive norm

ENH = 0 + Hmv + 0 + 0 + 0 = 0.405

FRH = Hind + Hmv + Hvp + Hme + Hme =0.857

GEH = Hind + Hmv + Hvp + Hme + Hme =1.08

ITH = Hind + Hmv + Hvp + Hme + Hme =0.88

FIH = Hind + Hmv + Hvp + Hme + Hme =2.32


Computed Entropy of constitutive norms (English, French, German, Italian and Fictitious)


Entropy results

  • In the EU Regulation according to the 5 categories of expression

    (1. Constitutive and performative norms, 2. Logical necessity, 3.Permissions and authorizations, 4.Capability, 5. Non-binding norms)

  • In the EU Secondary Legislation overall according to the 4 types of documents

    (Regulations, Decisions, Directives, Recommendations)


Entropy in the EU Regulation


Entropy resultsEU Regulation

  • Logical necessity, permissions and authorizations and capability(< entropy)

    • quite standardized in the 4 languages = almost equivalent translations

  • Constitutive performative norms(> entropy)

    • translation is more difficult to predict

    • Definitions, const. statements, obligations

    • FR: < entropy than IT

    • DE: > entropy (VP sein/haben…zu)


Entropy resultsEU Regulation

  • Non -binding norms

    • fairly amount of variation among the 4 languages

    • FR/IT: >entropy

    • DE: < entropy (should is most likely translated with sollen- Soll-Vorschriften)


Entropy overall the 4 EU documents


Entropy resultsEU Secondary Legislation

  • Regulations and Decisions(< entropy)

    • Direct applicability of the norms = more precision and standardization

    • FR looks more standardized than IT and DE

  • Directives(> entropy than Reg. and Dec.)

    • Binding only as to the result to be achieved

  • Recommendations (> entropy)

    • Not-binding: more freedom

    • DE : sollen



  • Given certain conditions, it is possible to predict with some certainty the occurrence of a particular factor

  • If applied to repetitive texts, entropy analysis can enhance research in langauge testing, evaluation and in the development of automated translation’s tools



  • Austin, J. L. 1962. How to do things with words.Oxford: Oxford University Press.

  • Coode, G. 1843. Legislative Expressions. Appendix to the Report of the Poor Law Commissioners on Local Taxation. Published separately 1845, 2nd Ed.1852.

  • Driedger, E. A. 1976. The Composition of legislation. Legislative forms and precedents(2nd Ed.). Ottawa:The Department of Justice

  • Shannon, Cand W. Weaver. 1963 (1949) The mathematical theory of communication. Urbana: University of Illinois Press.USA.

  • Thornton G.C. 1996. Legislative Drafting (4th Ed.). Butterworths, London.

  • http://publications.europa.eu/code/en/en-6000000.htm


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