?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Adc&rft.title=How+to+write+a+coequation&rft.creator=Dahlqvist%2C+Fredrik&rft.creator=Schmid%2C+Todd&rft.description=There+is+a+large+amount+of+literature+on+the+topic+of+covarieties%2C%0D%0Acoequations+and+coequational+specifications%2C+dating+back+to+the+early%0D%0Aseventies.+Nevertheless%2C+coequations+have+not+(yet)+emerged+as+an+everyday%0D%0Apractical+specification+formalism+for+computer+scientists.+In+this+review%0D%0Apaper%2C+we+argue+that+this+is+partly+due+to+the+multitude+of+syntaxes+for%0D%0Awriting+down+coequations%2C+which+seems+to+have+led+to+some+confusion+about+what%0D%0Acoequations+are+and+what+they+are+for.+By+surveying+the+literature%2C+we+identify%0D%0Afour+types+of+syntaxes%3A+coequations-as-corelations%2C+coequations-as-predicates%2C%0D%0Acoequations-as-equations%2C+and+coequations-as-modal-formulas.+We+present+each+of%0D%0Athese+in+a+tutorial+fashion%2C+relate+them+to+each+other%2C+and+discuss+their%0D%0Arespective+uses.&rft.publisher=Coalgebra&rft.date=2021-09-03&rft.type=Proceedings+paper&rft.language=eng&rft.source=+++++In%3A++Proceedings+of+the+9th+Conference+on+Algebra+and+Coalgebra+in+Computer+Science+(CALCO+2021).++++Coalgebra%3A+Salzburg%2C+Austria.+(2021)+++++&rft.format=text&rft.identifier=https%3A%2F%2Fdiscovery.ucl.ac.uk%2Fid%2Feprint%2F10146158%2F1%2F2109.11967v1.pdf&rft.identifier=https%3A%2F%2Fdiscovery.ucl.ac.uk%2Fid%2Feprint%2F10146158%2F&rft.rights=open