Should attribute GENRENAME in TGENRE be optional or required?

In Bio schema (defined as part of CHRONPROSE), GENRENAME is not optional:

<element name="TGENRE">
                            <a:documentation
                                xmlns:a="http://relaxng.org/ns/compatibility/annotations/1.0"
                                >GenreName (or tGenre) is used to tag the name of the genre
                                according to a project-generated list of genre
                                names.</a:documentation>
                            <attribute name="GENRENAME">
                                <a:documentation
                                    xmlns:a="http://relaxng.org/ns/compatibility/annotations/1.0"
                                    >GenreName is an optional attribute that provides a pick-list of
                                    possible genre names to modify the element tGenre. It will prove
                                    especially useful in situations where the prose does not allow
                                    the concise naming of a genre that would be easily understood by
                                    a simpler name. Ultimately, this attribute will help us
                                    systematize and index references to various genre
                                    names.</a:documentation>
                                <choice>
                                    <value>ABRIDGEMENT</value>
                                    <value>ACLEF</value>
                                    <value>ACROSTIC</value>
                                    <value>ADAPTATION</value>
                                    <value>ADVENTUREWRITING</value>
                                    <value>ADVERTISINGCOPY</value>
                                    <value>AFTERPIECE</value>
                                    <value>AFTERWORD</value>
                                    <value>AGITPROP</value>
                                    <value>ALLEGORY</value>
                                    <value>ALMANAC</value>
                                    <value>ANACREONTIC</value>
                                    <value>ANAGRAM</value>
                                    <value>ANNOTATION</value>
                                    <value>ANSWER</value>
                                    <value>ANTHEM</value>
                                    <value>ANTHOLOGY</value>
                                    <value>ANTIROMANCE</value>
                                    <value>APHORISM</value>
                                    <value>APOLOGY</value>
                                    <value>ARTCRITICISM</value>
                                    <value>AUTOBIOGRAPHY</value>
                                    <value>BALLAD</value>
                                    <value>BALLADE</value>
                                    <value>BALLADOPERA</value>
                                    <value>BALLET</value>
                                    <value>BERGAMASQUE</value>
                                    <value>BESTIARY</value>
                                    <value>BIBLICALPARAPHRASE</value>
                                    <value>BILDUNGSROMAN</value>
                                    <value>BIOGRAPHICALDICTIONARY</value>
                                    <value>BIOGRAPHY</value>
                                    <value>BISEXUALFICTION</value>
                                    <value>BLACKCOMEDY</value>
                                    <value>BOUTSRIMES</value>
                                    <value>BROADSIDE</value>
                                    <value>BURLETTA</value>
                                    <value>CABARET</value>
                                    <value>CAPTIVITYNARRATIVE</value>
                                    <value>CATECHISM</value>
                                    <value>CHAPBOOK</value>
                                    <value>CHARACTER</value>
                                    <value>CHARADE</value>
                                    <value>CHILDRENSLITERATURE</value>
                                    <value>CLERIHEW</value>
                                    <value>CLOSETDRAMA</value>
                                    <value>COLOURINGBOOK</value>
                                    <value>COMEDY</value>
                                    <value>COMEDYOFHUMOURS</value>
                                    <value>COMEDYOFINTRIGUE</value>
                                    <value>COMEDYOFMANNERS</value>
                                    <value>COMEDYOFMENACE</value>
                                    <value>COMICBOOK</value>
                                    <value>COMINGOUT</value>
                                    <value>COMMONPLACEBOOK</value>
                                    <value>COMPANION</value>
                                    <value>COMPUTERPROGRAM</value>
                                    <value>CONDITIONOFENGLANDNOVEL</value>
                                    <value>CONDUCTLITERATURE</value>
                                    <value>COOKBOOK</value>
                                    <value>COURTSHIPFICTION</value>
                                    <value>CRIMINOLOGY</value>
                                    <value>DEDICATION</value>
                                    <value>DETECTIVE</value>
                                    <value>DEVOTIONAL</value>
                                    <value>DIALOGUEORDEBATE</value>
                                    <value>DIARY</value>
                                    <value>DIALOGUEOFTHEDEAD</value>
                                    <value>DICTIONARY</value>
                                    <value>DIDACTIC</value>
                                    <value>DIRECTORY</value>
                                    <value>DISSERTATION</value>
                                    <value>DOCUMENTARY</value>
                                    <value>DOMESTIC</value>
                                    <value>DRAMA</value>
                                    <value>DRAMATICMONOLOGUE</value>
                                    <value>DREAMVISION</value>
                                    <value>DYSTOPIA</value>
                                    <value>ECLOGUE</value>
                                    <value>EDITING</value>
                                    <value>ELEGY</value>
                                    <value>ENCYCLOPAEDIA</value>
                                    <value>EPIC</value>
                                    <value>EPICTHEATRE</value>
                                    <value>EPIGRAM</value>
                                    <value>EPILOGUE</value>
                                    <value>EPISODICLITERATURE</value>
                                    <value>EPISTLE</value>
                                    <value>EPISTOLARY</value>
                                    <value>EPITAPH</value>
                                    <value>EPITHALAMIUM</value>
                                    <value>EPYLLION</value>
                                    <value>EROTICAPORNOGRAPHY</value>
                                    <value>ESSAY</value>
                                    <value>EULOGY</value>
                                    <value>EXHIBITIONCATALOGUE</value>
                                    <value>EXPRESSIONISTWRITING</value>
                                    <value>FABLE</value>
                                    <value>FABLIAU</value>
                                    <value>FAIRYTALE</value>
                                    <value>FANTASY</value>
                                    <value>FARCE</value>
                                    <value>FEMINIST</value>
                                    <value>FEMINISTTHEORY</value>
                                    <value>FICTION</value>
                                    <value>FILMTVSCRIPT</value>
                                    <value>FOLKSONG</value>
                                    <value>GARDENINGBOOK</value>
                                    <value>GENEALOGY</value>
                                    <value>GEORGIC</value>
                                    <value>GHOSTSTORY</value>
                                    <value>GIFTBOOK</value>
                                    <value>GOTHIC</value>
                                    <value>GOVERNMENTREPORT</value>
                                    <value>GRAMMAR</value>
                                    <value>GRAVEYARDPOETRY</value>
                                    <value>GUERILLATHEATRE</value>
                                    <value>GUIDEBOOK</value>
                                    <value>HAGIOGRAPHY</value>
                                    <value>HAIKU</value>
                                    <value>HARLEQUINADE</value>
                                    <value>HEROIC</value>
                                    <value>HISTORICAL</value>
                                    <value>HISTORY</value>
                                    <value>HYMN</value>
                                    <value>IMITATION</value>
                                    <value>IMPROVISATION</value>
                                    <value>INDUSTRIALNOVEL</value>
                                    <value>INTRODUCTION</value>
                                    <value>JOURNALISM</value>
                                    <value>JUVENILIA</value>
                                    <value>KITCHENSINKDRAMA</value>
                                    <value>KUNSTLERROMAN</value>
                                    <value>LAIS</value>
                                    <value>LAMPOON</value>
                                    <value>LEGALWRITING</value>
                                    <value>LEGENDFOLKTALE</value>
                                    <value>LESBIAN</value>
                                    <value>LETTER</value>
                                    <value>LETTERSFROMTHEDEADTOTHELIVING</value>
                                    <value>LIBRETTO</value>
                                    <value>LITERARYCRITICISM</value>
                                    <value>LITURGY</value>
                                    <value>LOVE</value>
                                    <value>LYRIC</value>
                                    <value>MAGICREALIST</value>
                                    <value>MANIFESTO</value>
                                    <value>MANUAL</value>
                                    <value>MAP</value>
                                    <value>MASQUE</value>
                                    <value>MEDICALWRITING</value>
                                    <value>MELODRAMA</value>
                                    <value>MIXEDMEDIA</value>
                                    <value>MOCKFORMS</value>
                                    <value>MONOLOGUE</value>
                                    <value>MORALITYMYSTERYPLAY</value>
                                    <value>MULTIMEDIA</value>
                                    <value>MUSICOLOGY</value>
                                    <value>MYSTERY</value>
                                    <value>MYTH</value>
                                    <value>NARRATIVEPOETRY</value>
                                    <value>NATIONALISTFICTION</value>
                                    <value>NATIONALTALE</value>
                                    <value>NOTEBOOK</value>
                                    <value>NOVEL</value>
                                    <value>NOVELLA</value>
                                    <value>NURSERYRHYME</value>
                                    <value>OBITUARY</value>
                                    <value>OCCASIONALPOETRY</value>
                                    <value>ODE</value>
                                    <value>ONEACTPLAY</value>
                                    <value>OPERA</value>
                                    <value>ORATORIO</value>
                                    <value>ORIENTAL</value>
                                    <value>PAGEANT</value>
                                    <value>PANEGYRIC</value>
                                    <value>PANTOMIME</value>
                                    <value>PARABLE</value>
                                    <value>PARATEXTS</value>
                                    <value>PARLIAMENTARYREPORT</value>
                                    <value>PARODY</value>
                                    <value>PASTORAL</value>
                                    <value>PEDAGOGY</value>
                                    <value>PERFORMANCEPOETRY</value>
                                    <value>PERIODICAL</value>
                                    <value>PETITION</value>
                                    <value>PHILOSOPHICAL</value>
                                    <value>PHILOSOPHY</value>
                                    <value>PICARESQUE</value>
                                    <value>PINDARIC</value>
                                    <value>POETRY</value>
                                    <value>POLEMIC</value>
                                    <value>POLITICALWRITING</value>
                                    <value>POPULAR</value>
                                    <value>PRAYER</value>
                                    <value>PREFATORYPIECE</value>
                                    <value>PROGRAMNOTES</value>
                                    <value>PROLETARIANWRITING</value>
                                    <value>PROLOGUE</value>
                                    <value>PROPAGANDA</value>
                                    <value>PROPHECY</value>
                                    <value>PSALM</value>
                                    <value>PSYCHOANALYTICAL</value>
                                    <value>QUIZ</value>
                                    <value>RADIODRAMA</value>
                                    <value>REALIST</value>
                                    <value>REGIONAL</value>
                                    <value>RELIGIOUS</value>
                                    <value>REVIEW</value>
                                    <value>REVUE</value>
                                    <value>RIDDLE</value>
                                    <value>ROMANCE</value>
                                    <value>SAGEWRITING</value>
                                    <value>SATIRE</value>
                                    <value>SCHOLARSHIP</value>
                                    <value>SCHOOLFICTION</value>
                                    <value>SCIENCEFICTION</value>
                                    <value>SCIENTIFICWRITING</value>
                                    <value>SCRAPBOOK</value>
                                    <value>SENSATIONNOVEL</value>
                                    <value>SENSIBILITY</value>
                                    <value>SENTIMENTAL</value>
                                    <value>SEQUEL</value>
                                    <value>SERMON</value>
                                    <value>SEXUALAWAKENINGFICTION</value>
                                    <value>SHORTSTORY</value>
                                    <value>SILVERFORKNOVEL</value>
                                    <value>SKETCH</value>
                                    <value>SKETCHBOOK</value>
                                    <value>SLAVENARRATIVE</value>
                                    <value>SOCIALSCIENCE</value>
                                    <value>SONG</value>
                                    <value>SONNET</value>
                                    <value>SPEECH</value>
                                    <value>STAGEREVIEW</value>
                                    <value>TESTIMONY</value>
                                    <value>TEXTBOOK</value>
                                    <value>THEATREOFCRUELTY</value>
                                    <value>THEATREOFTHEABSURD</value>
                                    <value>THEOLOGY</value>
                                    <value>THESAURUS</value>
                                    <value>THRILLER</value>
                                    <value>TOPOGRAPHICALPOETRY</value>
                                    <value>TRACTPAMPHLET</value>
                                    <value>TRAGEDY</value>
                                    <value>TRAGICOMEDY</value>
                                    <value>TRANSLATION</value>
                                    <value>TRAVELWRITING</value>
                                    <value>TREATISE</value>
                                    <value>UTOPIA</value>
                                    <value>VERSENOVEL</value>
                                    <value>VIGNETTE</value>
                                    <value>VILLANELLE</value>
                                    <value>YOUNGADULTWRITING</value>
                                </choice>
                            </attribute>
                            <data type="NCName"/>
                        </element>

In Writing, it is:


    <define name="TGENRE">
        <element name="TGENRE">
            <a:documentation xmlns:a="http://relaxng.org/ns/compatibility/annotations/1.0">GenreName
                (or tGenre) is used to tag the name of the genre according to a project-generated
                list of genre names.</a:documentation>
            <optional>
                <attribute name="GENRENAME">
                    <a:documentation xmlns:a="http://relaxng.org/ns/compatibility/annotations/1.0"
                        >GenreName is an optional attribute that provides a pick-list of possible
                        genre names to modify the element tGenre. It will prove especially useful in
                        situations where the prose does not allow the concise naming of a genre that
                        would be easily understood by a simpler name. Ultimately, this attribute
                        will help us systematize and index references to various genre
                        names.</a:documentation>
                    <choice>
                        <value>ABRIDGEMENT</value>
                        <value>ACLEF</value>
                        <value>ACROSTIC</value>
                        <value>ADAPTATION</value>
                        <value>ADVENTUREWRITING</value>
                        <value>ADVERTISINGCOPY</value>
                        <value>AFTERPIECE</value>
                        <value>AFTERWORD</value>
                        <value>AGITPROP</value>
                        <value>ALLEGORY</value>
                        <value>ALMANAC</value>
                        <value>ANACREONTIC</value>
                        <value>ANAGRAM</value>
                        <value>ANNOTATION</value>
                        <value>ANSWER</value>
                        <value>ANTHEM</value>
                        <value>ANTHOLOGY</value>
                        <value>ANTIROMANCE</value>
                        <value>APHORISM</value>
                        <value>APOLOGY</value>
                        <value>ARTCRITICISM</value>
                        <value>AUTOBIOGRAPHY</value>
                        <value>BALLAD</value>
                        <value>BALLADE</value>
                        <value>BALLADOPERA</value>
                        <value>BALLET</value>
                        <value>BERGAMASQUE</value>
                        <value>BESTIARY</value>
                        <value>BIBLICALPARAPHRASE</value>
                        <value>BILDUNGSROMAN</value>
                        <value>BIOGRAPHICALDICTIONARY</value>
                        <value>BIOGRAPHY</value>
                        <value>BISEXUALFICTION</value>
                        <value>BLACKCOMEDY</value>
                        <value>BOUTSRIMES</value>
                        <value>BROADSIDE</value>
                        <value>BURLETTA</value>
                        <value>CABARET</value>
                        <value>CAPTIVITYNARRATIVE</value>
                        <value>CATECHISM</value>
                        <value>CHAPBOOK</value>
                        <value>CHARACTER</value>
                        <value>CHARADE</value>
                        <value>CHILDRENSLITERATURE</value>
                        <value>CLERIHEW</value>
                        <value>CLOSETDRAMA</value>
                        <value>COLOURINGBOOK</value>
                        <value>COMEDY</value>
                        <value>COMEDYOFHUMOURS</value>
                        <value>COMEDYOFINTRIGUE</value>
                        <value>COMEDYOFMANNERS</value>
                        <value>COMEDYOFMENACE</value>
                        <value>COMICBOOK</value>
                        <value>COMINGOUT</value>
                        <value>COMMONPLACEBOOK</value>
                        <value>COMPANION</value>
                        <value>COMPUTERPROGRAM</value>
                        <value>CONDITIONOFENGLANDNOVEL</value>
                        <value>CONDUCTLITERATURE</value>
                        <value>COOKBOOK</value>
                        <value>COURTSHIPFICTION</value>
                        <value>CRIMINOLOGY</value>
                        <value>DEDICATION</value>
                        <value>DETECTIVE</value>
                        <value>DEVOTIONAL</value>
                        <value>DIALOGUEORDEBATE</value>
                        <value>DIARY</value>
                        <value>DIALOGUEOFTHEDEAD</value>
                        <value>DICTIONARY</value>
                        <value>DIDACTIC</value>
                        <value>DIRECTORY</value>
                        <value>DISSERTATION</value>
                        <value>DOCUMENTARY</value>
                        <value>DOMESTIC</value>
                        <value>DRAMA</value>
                        <value>DRAMATICMONOLOGUE</value>
                        <value>DREAMVISION</value>
                        <value>DYSTOPIA</value>
                        <value>ECLOGUE</value>
                        <value>EDITING</value>
                        <value>ELEGY</value>
                        <value>ENCYCLOPAEDIA</value>
                        <value>EPIC</value>
                        <value>EPICTHEATRE</value>
                        <value>EPIGRAM</value>
                        <value>EPILOGUE</value>
                        <value>EPISODICLITERATURE</value>
                        <value>EPISTLE</value>
                        <value>EPISTOLARY</value>
                        <value>EPITAPH</value>
                        <value>EPITHALAMIUM</value>
                        <value>EPYLLION</value>
                        <value>EROTICAPORNOGRAPHY</value>
                        <value>ESSAY</value>
                        <value>EULOGY</value>
                        <value>EXHIBITIONCATALOGUE</value>
                        <value>EXPRESSIONISTWRITING</value>
                        <value>FABLE</value>
                        <value>FABLIAU</value>
                        <value>FAIRYTALE</value>
                        <value>FANTASY</value>
                        <value>FARCE</value>
                        <value>FEMINIST</value>
                        <value>FEMINISTTHEORY</value>
                        <value>FICTION</value>
                        <value>FILMTVSCRIPT</value>
                        <value>FOLKSONG</value>
                        <value>GARDENINGBOOK</value>
                        <value>GENEALOGY</value>
                        <value>GEORGIC</value>
                        <value>GHOSTSTORY</value>
                        <value>GIFTBOOK</value>
                        <value>GOTHIC</value>
                        <value>GOVERNMENTREPORT</value>
                        <value>GRAMMAR</value>
                        <value>GRAVEYARDPOETRY</value>
                        <value>GUERILLATHEATRE</value>
                        <value>GUIDEBOOK</value>
                        <value>HAGIOGRAPHY</value>
                        <value>HAIKU</value>
                        <value>HARLEQUINADE</value>
                        <value>HEROIC</value>
                        <value>HISTORICAL</value>
                        <value>HISTORY</value>
                        <value>HYMN</value>
                        <value>IMITATION</value>
                        <value>IMPROVISATION</value>
                        <value>INDUSTRIALNOVEL</value>
                        <value>INTRODUCTION</value>
                        <value>JOURNALISM</value>
                        <value>JUVENILIA</value>
                        <value>KITCHENSINKDRAMA</value>
                        <value>KUNSTLERROMAN</value>
                        <value>LAIS</value>
                        <value>LAMPOON</value>
                        <value>LEGALWRITING</value>
                        <value>LEGENDFOLKTALE</value>
                        <value>LESBIAN</value>
                        <value>LETTER</value>
                        <value>LETTERSFROMTHEDEADTOTHELIVING</value>
                        <value>LIBRETTO</value>
                        <value>LITERARYCRITICISM</value>
                        <value>LITURGY</value>
                        <value>LOVE</value>
                        <value>LYRIC</value>
                        <value>MAGICREALIST</value>
                        <value>MANIFESTO</value>
                        <value>MANUAL</value>
                        <value>MAP</value>
                        <value>MASQUE</value>
                        <value>MEDICALWRITING</value>
                        <value>MELODRAMA</value>
                        <value>MIXEDMEDIA</value>
                        <value>MOCKFORMS</value>
                        <value>MONOLOGUE</value>
                        <value>MORALITYMYSTERYPLAY</value>
                        <value>MULTIMEDIA</value>
                        <value>MUSICOLOGY</value>
                        <value>MYSTERY</value>
                        <value>MYTH</value>
                        <value>NARRATIVEPOETRY</value>
                        <value>NATIONALISTFICTION</value>
                        <value>NATIONALTALE</value>
                        <value>NOTEBOOK</value>
                        <value>NOVEL</value>
                        <value>NOVELLA</value>
                        <value>NURSERYRHYME</value>
                        <value>OBITUARY</value>
                        <value>OCCASIONALPOETRY</value>
                        <value>ODE</value>
                        <value>ONEACTPLAY</value>
                        <value>OPERA</value>
                        <value>ORATORIO</value>
                        <value>ORIENTAL</value>
                        <value>PAGEANT</value>
                        <value>PANEGYRIC</value>
                        <value>PANTOMIME</value>
                        <value>PARABLE</value>
                        <value>PARATEXTS</value>
                        <value>PARLIAMENTARYREPORT</value>
                        <value>PARODY</value>
                        <value>PASTORAL</value>
                        <value>PEDAGOGY</value>
                        <value>PERFORMANCEPOETRY</value>
                        <value>PERIODICAL</value>
                        <value>PETITION</value>
                        <value>PHILOSOPHICAL</value>
                        <value>PHILOSOPHY</value>
                        <value>PICARESQUE</value>
                        <value>PINDARIC</value>
                        <value>POETRY</value>
                        <value>POLEMIC</value>
                        <value>POLITICALWRITING</value>
                        <value>POPULAR</value>
                        <value>PRAYER</value>
                        <value>PREFATORYPIECE</value>
                        <value>PROGRAMNOTES</value>
                        <value>PROLETARIANWRITING</value>
                        <value>PROLOGUE</value>
                        <value>PROPAGANDA</value>
                        <value>PROPHECY</value>
                        <value>PSALM</value>
                        <value>PSYCHOANALYTICAL</value>
                        <value>QUIZ</value>
                        <value>RADIODRAMA</value>
                        <value>REALIST</value>
                        <value>REGIONAL</value>
                        <value>RELIGIOUS</value>
                        <value>REVIEW</value>
                        <value>REVUE</value>
                        <value>RIDDLE</value>
                        <value>ROMANCE</value>
                        <value>SAGEWRITING</value>
                        <value>SATIRE</value>
                        <value>SCHOLARSHIP</value>
                        <value>SCHOOLFICTION</value>
                        <value>SCIENCEFICTION</value>
                        <value>SCIENTIFICWRITING</value>
                        <value>SCRAPBOOK</value>
                        <value>SENSATIONNOVEL</value>
                        <value>SENSIBILITY</value>
                        <value>SENTIMENTAL</value>
                        <value>SEQUEL</value>
                        <value>SERMON</value>
                        <value>SEXUALAWAKENINGFICTION</value>
                        <value>SHORTSTORY</value>
                        <value>SILVERFORKNOVEL</value>
                        <value>SKETCH</value>
                        <value>SKETCHBOOK</value>
                        <value>SLAVENARRATIVE</value>
                        <value>SOCIALSCIENCE</value>
                        <value>SONG</value>
                        <value>SONNET</value>
                        <value>SPEECH</value>
                        <value>STAGEREVIEW</value>
                        <value>TESTIMONY</value>
                        <value>TEXTBOOK</value>
                        <value>THEATREOFCRUELTY</value>
                        <value>THEATREOFTHEABSURD</value>
                        <value>THEOLOGY</value>
                        <value>THESAURUS</value>
                        <value>THRILLER</value>
                        <value>TOPOGRAPHICALPOETRY</value>
                        <value>TRACTPAMPHLET</value>
                        <value>TRAGEDY</value>
                        <value>TRAGICOMEDY</value>
                        <value>TRANSLATION</value>
                        <value>TRAVELWRITING</value>
                        <value>TREATISE</value>
                        <value>UTOPIA</value>
                        <value>VERSENOVEL</value>
                        <value>VIGNETTE</value>
                        <value>VILLANELLE</value>
                        <value>YOUNGADULTWRITING</value>
                    </choice>
                </attribute>
            </optional>
            <oneOrMore>
                <choice>
                    <text/>
                    <ref name="BIBCITS"/>
                    <ref name="DATE"/>
                    <ref name="EMPH"/>
                    <ref name="FOREIGN"/>
                    <ref name="NAME"/>
                    <ref name="ORGNAME"/>
                    <ref name="PLACE"/>
                    <ref name="PLITERARYSCHOOLS"/>
                    <ref name="QUOTE"/>
                    <ref name="RESEARCHNOTE"/>
                    <ref name="SIC"/>
                    <ref name="SOCALLED"/>
                    <ref name="TCHARACTERNAME"/>
                    <ref name="TCHARACTERTYPEROLE"/>
                    <ref name="TGENRE"/>
                    <ref name="TITLE"/>
                    <ref name="TMOTIF"/>
                    <ref name="TOPIC"/>
                    <ref name="TTHEMETOPIC"/>
                    <ref name="TVOICENARRATION"/>
                </choice>
            </oneOrMore>
        </element>
    </define>

cwrc / CWRC-Schema

Should attribute GENRENAME in TGENRE be optional or required? #169