Hi Leo, In pure semantic terms I appreciate the difference but this is practically of no value.
What does this empty string mean? Is it? a) The doctor simply did not add any comment. b) The doctor purposefully 'added an empty string' by clicking through the data entry widget, perhaps to signify 'no comment'. c) The doctor couldn't add a comment for some other technical / environmental reason. These are very subtle differences to most clinical staff and I would not want to base any safe querying on assumptions that clinicians would record these differences reliably. If there is a need to positively identify 'no comment', I would model that explicitly but this is rare in clinical practice, and usually is recorded for medico-legal reasons rather than future querying e.g. 'No known allergies' is a legitimate clinical comment but cannot ever be safely queried upon, since the next clinical statement in the record might well be 'Diagnosis = Penicillin Allergy'. The most significant principle is that we do not normally record 'empty data' at all in openEHR. The data simply does not exist in the clinical record. If some sort of comment is mandatory then using the null is the means to allow an empty comment. I have copied ot the clinical list, as it would be interesting to get some other feedback. Ian Dr Ian McNicoll office / fax +44(0)141 560 4657 mobile +44 (0)775 209 7859 skype ianmcnicoll ian.mcnicoll at oceaninformatics.com ian at mcmi.co.uk Clinical Analyst Ocean Informatics openEHR Archetype Editorial Group Member BCS Primary Health Care SG Group www.phcsg.org / BCS Health Scotland On 29 June 2010 12:26, Leonardo Moretti <lmoretti at noemalife.com> wrote: > > Hi Ian, > in my opinion an empty string has a semantic difference with a null value. > Empty string is however a valid value. For example, I could have different > cases for "Comment" in openEHR-EHR-OBSERVATION.blood_pressure.v1: > - a non-empty string with the comment on blood pressure measurement. > - an empty string, meaning that no comment has been given from the doctor, > because not needed (doctor judges that no comment is necessary) > - a null value, meaning that no comment has been asked to the doctor, > because exluded from the template/GUI. > Or there are an other way to model these three cases? > > Regards, > leo > > > > Ian McNicoll-3 wrote: > > > > Hi Leo, > > > > An important principle under-pinning openEHR is that 'empty' data is not > > normally recorded, which is consistent with general clinical practice > > information recording. > > > > On this basis, I am not sure I can see the use case for recording "" i.e. > > Empty text. If a text data entry field is left blank, this would simply > > not > > be recorded in openEHR data. If the field is mandatory, either the user > is > > forced to make some sort of entry or perhaps is allowed to select one of > > the > > null values as you suggest. > > > > Regards, > > > > Ian > > > > Dr Ian McNicoll > > office / fax +44(0)141 560 4657 > > mobile +44 (0)775 209 7859 > > skype ianmcnicoll > > ian.mcnicoll at oceaninformatics.com > > ian at mcmi.co.uk > > > > Clinical Analyst Ocean Informatics openEHR Archetype Editorial Group > > Member BCS Primary Health Care SG Group www.phcsg.org / BCS Health > > Scotland > > > > > > > > On 25 June 2010 16:07, Moretti Leonardo <lmoretti at noemalife.com> wrote: > > > >> In > >> http://www.openehr.org/releases/1.0.2/architecture/rm/data_types_im.pdf > , > >> DV_TEXT is defined as a text item. Among "Invariants" (page 29), I found > >> that this data type is valid if it is not empty (Value_valid: value /= > >> void and then not value.is_empty and then not(value.has(CR) or > >> value.has(LF))). > >> > >> Does this mean empty string is not a valid value for DV_TEXT? If so, why > >> empty string cannot be a valid value? An empty string could be > >> meaningful, with a different semantic than null value! Many textual > >> information could be an empty string (comments, descritpions..). An > >> empty string means that the value is exactly a void string, a null value > >> means that the information is unknown, not taken, not asked! > >> > >> Regards > >> leo > >> > >> _______________________________________________ > >> openEHR-technical mailing list > >> openEHR-technical at openehr.org > >> http://lists.chime.ucl.ac.uk/mailman/listinfo/openehr-technical > >> > > > > _______________________________________________ > > openEHR-technical mailing list > > openEHR-technical at openehr.org > > http://lists.chime.ucl.ac.uk/mailman/listinfo/openehr-technical > > > > > > -- > View this message in context: > http://old.nabble.com/Empty-string-for-DV_TEXT-tp28993527p29022604.html > Sent from the openehr-technical mailing list archive at Nabble.com. > > _______________________________________________ > openEHR-technical mailing list > openEHR-technical at openehr.org > http://lists.chime.ucl.ac.uk/mailman/listinfo/openehr-technical > -------------- next part -------------- An HTML attachment was scrubbed... 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