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h1. OA vs OAC
Currently RS uses [Open Annotation Collaboration (OAC)] version 201110 for [Data Annotation|Open Annotation Collaboration (OAC)#Annotation with OAC and Reification] and [Image Annotation|Image Annotation Design#OAC Representation].
A [W3C Annotation Community Group|] was chartered to merge [AO|] and OAC.
The result is a draft version 201205 of a merged AO and OAC ontology, called Open Annotation (OA) ontology.

- [Core spec|]
- [Extension spec|]
- [Annotation Cookbook examples|]
- [MapHub examples|]

h2. Major changes
- OA does not define classes for [Body|] and [Target|], i.e. oa:Target and oa:Body are GONE!. Instead, the body and target should have:
-- type of content, [represented as a DCMI type|], eg
{code}a dctype:Text{code}
-- be of any media type, represented as a MIME type, eg
{code}dc:format "text/html"{code}
- provenance is now represented with oa:annotator (subProperty of dcterms:creator) and oa:annotated (subProperty of dcterms:created)
- modelVersion: there SHOULD be exactly 1 per Annotation:
{code}oa:modelVersion <>{code}
- instead of a fragment selector at the URI (#xywh=50,20,200,200), [now uses|] a node oa:FragmentSelector with rdf:value="xywh=50,20,200,200"

h2. Other notes
- [Extension Annotation Classes|] defines an appropriate class: oax:Bookmark
- oax:Bookmark usually has [no body|], but could have a Comment body
- oax:Bookmark with a [comment body|], stored as cnt:chars in cnt:ContentAsText.
Uses oa:annotator, oa:annotated (not DC terms).
- [Target resource|] has rdf:type dt:Text and dc:format "text/html"
- Image is a [dcterms:StillImage|] and has dc:format "image/jp2".
TODO: shouldn't this be dcmitype:StillImage (not dcterms:StillImage nor dcmitype:Image).
Annotated point is represented with xywh oa:FragmentSelector where w=h=1
- [List of annotations|] uses OAI ORE (Object Reuse and Exchange):
a ore:Aggregation that has ore:aggregates links to the individual items

h2. Used ontologies and Prefixes
OA uses the following ontologies and prefixes:
| *Pref* | *URI* | *Get from URL* | *Local file* |
| cnt | | | content.rdf |
| dc | | no need | |
| dcterms | | no need | |
| dctype | | no need | |
| oa | | | oa-core.rdf |
| oax | | | oa-extension.rdf |
| ore | | no need | |
| rdf | | no need | |

h2. Migration from OAC to OA
It would be best to update Data Annotation and Image Annotation to use the new version (OA). This won't be hard, see the changes above.
The priority of this task is not determined and it is not scheduled yet.

We considered using OA as main ontology for [Data Basket Design]. However, we gave up on this idea.
In order to have a simple and coherent model, Basket uses OAC, same as Data+Image Annotation.