Circa. dates

Hi all,

With colleagues I have been looking at how we might handle historical approximate dates in Schema.org<http://Schema.org>.  The initial requirement being to be able to describe an old book or manuscript published say in approximately 1765.  A common need in the bibliographic world, with the normal string based solution being “circa. 1765”, or “c. 1765” - Wikipedia providing some examples<http://en.wikipedia.org/wiki/Circa>.

The knee-jerk reaction was to suggest some sort of approximateDateCreated property for CreativeWork which would not only help us bibliographic folks but also those in museums and galleries with similar date approximation needs.

Broadening the analysis it became clear that this need could be applicable in most any case where you would expect a Date<http://schema.org/Date> in the range of a property.  birthDate, deathDate, dateCreated, datePublished, foundingDate, all being all potential candidates for Circa style dates.  Rolling things into the future you could imagine other examples such as wanting to describe the last serviced date of a vehicle being circa 2013.

So how to solve this in a simple, yet generic, way?

We could take advantage of the default "if you haven’t got a specified type for a property, a Text is acceptable” pattern in Schema, and just put in a text string with a defined format: “c.1765”.

Perhaps a more appropriate solution would be to define a new data type, to be added to the range of suitable properties.

My pragmatic (KISS and don’t break stuff) view of this leads me to suggest a new data type named ‘circaData’, or maybe 'approximateDate' as a subType of Date.  With descriptive information in the Type definition explaining why/how you would use it in the use cases I describe above.

This approach would add this important functionality, for those describing old stuff, without the need for major upheaval across the vocabulary, and would at least default to a date for those that do not care or look for such approximation aspect of dates.

~Richard