Ahmetovic, D.

Armano, T.

Bernareggi, C.

Berra, M.

Capietto, A.

Coriasco, S.

Murru, N.

Ruighi, A.

English

Institutional Research Information System University of Turin

Axessibility: creating PDF documents withaccessible formulaeD. Ahmetovic, T. Armano, M. Berra, C. Bernareggi, A. Capietto, S. Coriasco, N. Murru, A. RuighiSommarioI documenti PDF contenenti formule generati daLATEX non sono solitamente accessibili median-te tecnologie assistive per persone con disabilitàvisive (i.e., screen reader e barre Braille). Il pac-chetto LATEX axessibility.sty da noi sviluppatorisolve questo problema, permettendo di creare do-cumenti PDF in cui le formule vengono lette datali tecnologie assistive. Infatti, vengono generatiautomaticamente dei commenti nascosti nel docu-mento PDF (mediante l’attributo /ActualText)in corrispondenza di ogni formula. Tale testo alter-nativo risulta nascosto nel documento PDF, magli screen reader Jaws, NVDA e VoiceOver vi ac-cedono correttamente. Inoltre, abbiamo creato deidizionari (in inglese e italiano) per NVDA e Jawsche forniscono la lettura delle formule in linguag-gio naturale nel caso in cui l’utente non conosca icomandi LATEX. Il pacchetto non genera PDF/UA.AbstractPDF documents containing formulae generated byLATEX are usually not accessible by assistive tech-nologies for visually impaired people (i.e., by screenreaders and braille displays). The LATEX pack-age axessibility.sty that we developed man-ages this issue, allowing to create PDF documentswhere the formulae are read by these assistivetechnologies, since it automatically generates hid-den comments in the PDF document (using the/ActualText attribute) in correspondence to eachformula. This actual text is hidden in the PDF doc-ument, but the screen readers Jaws, NVDA andVoiceOver read it correctly. Moreover, we have cre-ated NVDA and Jaws dictionaries (in English andin Italian) that provide the reading in the natu-ral language in the case that the user does notknow the LATEX commands. The package does notgenerate PDF/UA.1 IntroductionIn this paper, we describe axessibility.sty, aLATEX package which allows to automatically gene-rate a PDF document with formulae accessible byassistive technologies for visually impaired people.Assistive technologies (screen readers and brailledisplays) perform satisfactorily with regard to digi-tal documents containing text, but they still havea long way to go as far as formulae and graphsare concerned. A comprehensive overview aboutthis problem can be found in Archambault et al.(2007) and Armano et al. (2014).Many studies have been conducted in order toimprove the accessibility of digital documents withmathematical contents. For instance, MathPlayerensures accessibility of formulae inserted by usingMathType in Word documents Soiffer (2018).Another way for creating accessible mathemati-cal documents is given by the MathML language(see Bernareggi e Archambault (2007) for fur-ther information). However, accessibility of suchdocuments is heavily affected by the versions ofbrowsers, operating systems and screen readers,making this solution very unstable. A system usedby blind people for reading and writing mathema-tics is the LAMBDA system (Linear Access to Ma-thematics for braille Device and Audio-synthesis).Mathematical language in LAMBDA is designed sothat every symbol can be directly translated intowords. For further details on LAMBDA we refer toBernareggi (2010). Unfortunately, this systemdoes not help to spread accessible digital docu-ments, since it is only used by visually impairedpeople and it is not a standard for the realizationof documents by sighted people. Regarding LATEX,assistive technologies can directly manage LATEXdocuments. In this case, visually impaired peopleneed to learn LATEX in order to understand thecommands. However, there are software which fa-cilitate LATEX comprehension and usability; one ofthem is BlindMath Pepino et al. (2006). Moreover,some converters from LATEX to braille exist, see,e.g., Papasalouros e Tsolomitis (2017) andBatusic et al. (1998).In general, the most widespread digital docu-ments are in PDF format. However, in the case ofmathematical contents, they are not accessible atall, since formuale are usually unreadable by screenreaders because they are bidimensional as images.None of the above systems allows to directly pro-duce accessible formulae in PDF documents. Thiscould be possible only performing specific tasks.For instance, using the Word editor, if each formulais manually tagged by the author (by using the al-ternative text), such a comment will be kept whenthe corresponding PDF file will be generated andit will be read by the screen reader. However, this1D. Ahmetovic, T. Armano, M. Berra, C. Bernareggi, A. Capietto, S. Coriasco, N. Murru, A. RuighiArsTEXnica Nº 0, Dicembre 2099procedure does not help to improve the presence ofaccessible PDF documents, since it is a very boringand time consuming method. It is very hard tothink that an author performs these actions for therealization, e.g., of a book. Currently, a standardand fast method for inserting accessible formulaeinto a PDF documents is still lacking despite it isa very important issue for spreading accessible di-gital scientific documents. In Uebelbacher et al.(2014) standard guidelines for accessibility of PDFdocuments are presented. Moreover, in Moore(2009), Moore (2014) and Borsero et al. (2016),an overview about accessibility of PDF documentsis provided with a focus on mathematical contents.In this paper, we show the features of the packa-ge axessibility.sty (whose a first version is alsodescribed in Armano et al. (2018)) that providesthe first method for an automatized productionof accessible PDF documents with mathematicalcontents. We would like to highlight that this pac-kage does not produces fully tagged PDF, suchas the standard PDF/UA, but it allows to obtaina PDF where formulae are described using the/ActualText attribute.2 Problem StatementWhen a PDF document is generated starting fromLATEX, formulae are not accessible by screen rea-ders and braille displays. They can be made ac-cessible by inserting a hidden comment, i.e., anactual text, similarly to the case of web pages orWord documents. This can be made, e.g., by usingthe LATEX package pdfcomment.sty or using aneditor for PDF files like Adobe Acrobat Pro. Inany case, this task must be manually performedby the author and it is surely inefficient, since theauthor should write the formulae and, in addition,insert a description for each formula. Note alsothat the package pdfcomment.sty does not allowto insert special characters like backslash, brace, etc,in the comment. Moreover, with these solutions,the reading is bothered, since the screen readerreads incorrectly the formula and then the correctcomment of the formula.In Figure 1, we show the PDF document gene-rated from the following LATEX code containing asimple formula with a comment manually inserted.\documentclass{article}\documentclass[a4paper ]{ article}\usepackage{pdfcomment}\begin{document}A simple formula:\begin{equation}\pdftooltip{\frac{1 + \sqrt {5}}{2}}{begin fraction numerator 1 +square root of 5 over 2end fraction}\end{equation}\end{document}When the screen reader accesses the PDFdocument, the formula will be readsquare root 1 plus 5 2 begin fraction nu-merator 1 plus square root of 5 over 2end fractioni.e., before reading the correct commentbegin fraction numerator 1 plus squareroot of 5 over 2 end fractionthe screen reader reads incorrectly the formulasquare root 1 plus 5 2.Figura 1: PDF document generated using the packagepdfcomment.styThere are also some LATEX packages that tryto improve the accessibility of PDF documentsproduced by LATEX. In particular the packagesaccsupp.sty1 and accessibility_meta.sty2 has beendeveloped in order to obtain tagged PDF docu-ments. However, both packages do not solve theproblem of the accessibility of formulae.3 axessibility.sty LATEX packageOur package, named axessibility.sty, solvesthe problem described in the previous section. Itachieves that by inserting a hidden comment in thePDF file corresponding to any given formula. Thiscomment, named /ActualText, contains the origi-nal LATEX commands used to generate the formula.The hidden comment is read by screen readers andbraille displays instead of the ASCII representationof the formula, which is often incorrect.3.1 UsageAuthors that would like to create an accessiblePDF document for visually impaired people onlyneed to include the axessibility.sty packageinto the preamble of their LATEX project. Mathe-matical environments will then automatically pro-duce the /ActualText content and include it inthe produced PDF file.We have treated the most used environments forinserting formulae, i.e., equation, equation*, \[,1. available at https://ctan.org/pkg/accsupp2. available at https://github.com/AndyClifton/AccessibleMetaClass2ArsTEXnica Nº 0, Dicembre 2099 Axessibility: creating PDF documents with accessible formulae\(. Hence, any formula inserted using one of theseenvironments is accessible in the correspondingPDF document. Additionally, the package enablesto copy the formula LATEX code from the PDFreader and paste it elsewhere.Note that, to preserve the compatibility withAcrobat Reader, our package discourages the useof the underscore character _ which is not correctlyread using screen readers in combination with thisPDF reader. Alternatively, we suggest to use theequivalent command \sb.In-lined and display mathematical modes ($, $$)are not supported in this version of the package.However external scripts provided as companionsoftware can also address these use cases.If we use the package axessibility.sty ap-plied to the previous example, we obtain thefollowing LATEX code.\documentclass[a4paper ,11pt]{ article}\usepackage{axessibility}\begin{document}A simple formula:\begin{equation}\frac{1 + \sqrt {5}}{2}\end{equation}\end{document}We observe that, in this case, the author has to wri-te the formula without adding anything else. More-voer, inside the source code of the PDF file, we findan /ActualText tag with the LATEXcode inside, au-tomatically generated by the axessibility.stypackage./S/Span <</ ActualText (\040\040\\frac \040{1\040+\040\\ sqrt\040{5}}{2}\040) >>BDCThe screen reader will read correctly the LATEXcommand \frac {1+ \sqrt {5}}{2}. Moreover,we have created JAWS and NVDA dictionariesthat provide the reading in the natural languagein the case that the user does not know the LATEXcommands.3.2 Technical Overviewaxessibility.sty first defines a pair ofinternal commands (\BeginAxessible and\EndAxessible) which redefine \BeginAccSuppand \EndAccSupp as follows:\newcommand *{\ BeginAxessible }[1]{%\begingroup\setkeys{ACCSUPP }{#1}%\edef\ACCSUPP@span{%/S/Formula <<%\ifx\ACCSUPP@Alt\relax\else/Alt\ACCSUPP@Alt\fi\ifx\ACCSUPP@ActualText\relax\else/ActualText\ACCSUPP@ActualText\fi>>%}%\ACCSUPP@bdc\ACCSUPP@space\endgroup}Precisely, \BeginAxessible adds a hidden com-ment that starts with /S/Formula instead of/Span.\newcommand *{\ EndAxessible }{%\begingroup\ACCSUPP@emc\endgroup}The second building block of this package is thewrapper. This routine takes the LATEX code insidethe formula, removes the tokens and passes it to\BeginAxessible.\long\def\wrap #1{\BeginAxessible{method=escape ,ActualText =\ detokenize\expandafter{#1}, Alt=\ detokenize\expandafter{#1} }#1\EndAxessible%}Finally, using the wrapper, we can re-define themathematical environments using the commandabove. Here is an example using equation.\renewenvironment{equation }{%\incr@eqnum\mathdisplay@push\st@rredfalse \global\@eqnswtrue\mathdisplay{equation}%\collect@body\wrap\auxiliaryspace }{%\endmathdisplay{equation}%\mathdisplay@pop\ignorespacesafterend}4 Conclusions and Future WorkWe have developed a LATEX package that automa-tically generates comments to formulae when thePDF document is produced by LATEX. The com-ments are hidden in the PDF document and theycontain the LATEX commands that generate the for-mulae. In this way, an accessible PDF documentcontaining formulae is generated. Indeed, screenreaders are able to access the comment when pro-cessing a formula and reading it. Moreover, wehave created JAWS and NVDA dictionaries thatprovides the reading in the natural language inthe case that the user does not know the LATEXcommands.There are a few issues that are yet to be solvedwith a pure LATEX solution. Namely,3D. Ahmetovic, T. Armano, M. Berra, C. Bernareggi, A. Capietto, S. Coriasco, N. Murru, A. RuighiArsTEXnica Nº 0, Dicembre 2099• In-line and displayed mathematical environ-ments delimited with $, $$,• User-defined Macros,• Multi-line environments such as \align and\eqnarray.• Semantic description of formulae.• PDF/UA.We have resolved the first two problems using an ex-ternal script – axesscleaner.py – coded in Perland Python. The script also beautifies the LATEXfile and removes all the underscore characters _,replacing those with \sb. Using this solution weare now able to apply axessibility.sty to enti-re textbooks that were written without using thepackage in the first place.Multi-line environments are going to be treatedusing a LATEX solution that is currently in thetest phase. Concerning the last two problems amore in-depth research is in order. The authorsare currently initiating the investigation to addressthese issues as a future work.5 AcknowledgementsThe authors wish to thank the bank foundation‘Fondazione Cassa di Risparmio di Torino’, Leo-Club (Biella, Italy) and the several volunteers withvisual impairment who provided their fundamentalcontribution.Riferimenti bibliograficiArchambault, D., Stoger, B., Fitzpatrick,D. e Miesenberger, K. (2007). «Access toscientific content by visually impaired people».Upgrade.Armano, T., Capietto, A., Illengo, M., Mur-ru, N. e Rossini, R. (2014). «An overviewon ict for the accessibility of scientific texts byvisually impaired students». In SIREM-SIE-LConference.Armano, T., Capietto, A., Coriasco, S., Mur-ru, N., Ruighi, A. e Taranto, E. (2018). «Anautomatized method based on latex for the rea-lization of accessible pdf documents containingformulae». In Computers Helping People withSpecial Needs. Springer.Batusic, M., Miesenberger, S., K. e LaBra-Door, B. (1998). «a contribution to makingmathematics accessible for the blind». In In-ternational Conference on Computers HelpingPeople with Special Needs. Springer.Bernareggi, C. (2010). «Non-sequential mathe-matical notations in the lambda system». InComputers Helping People with Special Needs.Springer.Bernareggi, C. e Archambault, D. (2007).«Mathematics on the web: emerging opportuni-ties for visually impaired people». In Conferenceon Web accessibility. ACM.Borsero, M., Murru, N. e Ruighi, A. (2016).«Il latex come soluzione al problema dell’accessoa testi con formule da parte di disabili visivi».ArsTeXnica.Moore, R. (2009). «Ongoing efforts to generatetagged pdf using pdftex». TUGboat.— (2014). «Pdf/a-3u as an archival format foraccessible mathematics». In Watt, CICM.Papasalouros, A. e Tsolomitis, A. A. (2017).«direct tex-to-braille transcribing method».Science Education for Students with Disabilities.Pepino, A., Freda, C., Ferraro, F., Paglia-ra, S. e Zanfardino, F. (2006). «“blindmath”a new scientific editor for blind students». InComputers Helping People with Special Needs.Springer.Soiffer, N. (2018). «Mathplayer: web-based mathaccessibility». In Conference on Computers andAccessibility. ACM.Uebelbacher, A., Bianchetti, R. e Riesch,M. (2014). «Pdf accessibility checker (pac 2):The first tool to test pdf documents for pdf/uacompliance». In Computers Helping People withSpecial Needs. Springer.. D. AhmetovicDipartimento di Matematica "G.Peano", Università degli Studi diTorinodragan.ahmetovic@unito.it. T. ArmanoDipartimento di Matematica "G.Peano", Università degli Studi diTorinotiziana.armano@unito.it. M. BerraDipartimento di Matematica "G.Peano", Università degli Studi diTorinomichele.berra@unito.it. C. BernareggiDipartimento di Informatica, Univer-sità di Milanocristian.bernareggi@unimi.it4ArsTEXnica Nº 0, Dicembre 2099 Axessibility: creating PDF documents with accessible formulae. A. CapiettoDipartimento di Matematica "G.Peano", Università degli Studi diTorinoanna.capietto@unito.it. S. CoriascoDipartimento di Matematica "G.Peano", Università degli Studi diTorinosandro.coriasco@unito.it. N. MurruDipartimento di Matematica "G.Peano", Università degli Studi diTorinonadir.murru@unito.it. A. RuighiDipartimento di Matematica "G.Peano", Università degli Studi diTorinoalice.ruighi@unito.it5

Axessibility: creating PDF documents with accessible formulae

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Axessibility: creating PDF documents with accessible formulae

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