OA motivations and triple-based annotations

Hi all,

I'd like to get some feedback on the use of OA to preserve and share 
data created using Timeline JS (via http://timeline.knightlab.com/) and 
TimeMapper(http://timemapper.okfnlabs.org/) as annotations that an be 
contributed to a broader data set.   I don't necessarily want to 
preserve all the data in the timeline in this case, just the association 
of a resource with a date (or a date and a place in the case of the 
TimeMapper tool).

So, e.g. given the following data from a timeline:

Start Date  End Date  Headline  Text  Media  Media Credit  Media 
Caption  Media Thumbnail  Type  Tag
-760 BCE  -710 BCE  Il. 14.319  "nor of Danaë of the fair ankles, 
daughter of Acmsius, [320] who bare Perseus, pre-eminent above all 
warriors;" 
http://data.perseus.org/citations/urn:cts:greekLit:tlg0012.tlg001:14.319 
<//www.google.com/url?q=http%3A%2F%2Fwww.perseus.tufts.edu%2Fhopper%2Ftext%3Fdoc%3DHom.%2BIl.%2B14.319%26fromdoc%3DPerseus%253Atext%253A1999.01.0134> 
 Perseus Project Tufts University  
 
 
 Greek Text


Whose source is a google spreadsheet at 
https://docs.google.com/spreadsheets/d/1MtN2tLKhTYuaLGWTArh5IJJCTc1BCJDjSx2lA8iWZME/edit#gid=494070028

I might serialize an annotation as:

@prefixcnt:<http://www.w3.org/2011/content#> .
@prefixdcmit:<http://purl.org/dc/dcmitype/> .
@prefixoa:<http://www.w3.org/ns/oa#> .
@prefixperseus:<http://data.perseus.org/> .

<perseus:annotationsurn:cite:perseus:pdlann.1>  aoa:Annotation;
     oa:annotatedBy<perseus:sosol/users/JohnSmith>  ;
     oa:hasBody<perseus:annotations/urn:cite:perseus:pdlann.1/tag>  ;
     oa:hasTarget<perseus:citations/urn:cts:greekLit:tlg0012.tlg001:14.319>  ;
     oa:motivatedByoa:tagging.

<perseus:annotationsurn:cite:perseus:pdlann.1/tag>  adcmit:Date,
         cnt:ContentAsText,
         oa:Tag;
     cnt:chars"-0760/-0710";
     oa:hasSource<https://docs.google.com/spreadsheets/d/1MtN2tLKhTYuaLGWTArh5IJJCTc1BCJDjSx2lA8iWZME/edit#gid=494070028>  .


In an ideal world, I could use a semantic tag for the date, but I'm not 
aware of any that would work here.  I think the alternative approach 
might be to use an extension of oa:motivation to indicate the motivation 
is assigning a date to the target resource.

I'd love to get some feedback on whether this approach makes sense, if 
anyone has done something similar already, or if there are any 
suggestions for ways to do this better.

Thanks!
Bridget