Open Annotation (OA)

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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|http://www.w3.org/community/openannotation/] was chartered to merge [AO|http://code.google.com/p/annotation-ontology/] and OAC.
The result is a draft version 201205 of a merged AO and OAC ontology, called Open Annotation (OA) ontology.

Links:
- [Core spec|http://www.openannotation.org/spec/core/]
- [Extension spec|http://www.openannotation.org/spec/extension/]
- [Annotation Cookbook examples|http://www.w3.org/community/openannotation/wiki/Cookbook]
- [MapHub examples|http://maphub.github.com/api/]

h2. Major changes
- OA does not define classes for [Body|http://www.openannotation.org/spec/core/#BodyResource] and [Target|http://www.openannotation.org/spec/core/#TargetResource], i.e. oa:Target and oa:Body are GONE!. Instead, the body and target should have:
-- type of content, [represented as a DCMI type|http://www.openannotation.org/spec/extension/#ResourceClass], 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 <http://www.w3.org/ns/openannotation/core/20120509>{code}
- instead of a fragment selector at the URI (#xywh=50,20,200,200), [now uses|http://www.w3.org/community/openannotation/wiki/Sopa_Selector] a node oa:FragmentSelector with rdf:value="xywh=50,20,200,200"

h2. Other notes
- [Extension Annotation Classes|http://www.openannotation.org/spec/extension/#AnnotationClass] defines an appropriate class: oax:Bookmark
- oax:Bookmark usually has [no body|http://www.w3.org/community/openannotation/wiki/Sopa_Bodyless], but could have a Comment body
- oax:Bookmark with a [comment body|http://www.w3.org/community/openannotation/wiki/SE_Bookmarking_a_Webpage], stored as cnt:chars in cnt:ContentAsText.
Uses oa:annotator, oa:annotated (not DC terms).
- [Target resource|http://www.w3.org/community/openannotation/wiki/Sopa_Target_Resource] has rdf:type dt:Text and dc:format "text/html"
- Image is a [dcterms:StillImage|http://maphub.github.com/api/#georef_example] 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|http://maphub.github.com/api/#annotation_index] 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 | http://www.w3.org/2011/content# | http://www.w3.org/2011/content | content.rdf |
| dc | http://purl.org/dc/elements/1.1/ | no need | |
| dcterms | http://purl.org/dc/terms/ | no need | |
| dctype | http://purl.org/dc/dcmitype/ | no need | |
| oa | http://www.w3.org/ns/openannotation/core/ | http://www.openannotation.org/spec/core/core-schema.xml | oa-core.rdf |
| oax | http://www.w3.org/ns/openannotation/extension/ | http://www.openannotation.org/spec/extension/extension-schema.xml | oa-extension.rdf |
| ore | http://www.openarchives.org/ore/terms/ | no need | |
| rdf | http://www.w3.org/1999/02/22-rdf-syntax-ns# | 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.