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{toc}
{jira:RS-1472}
{jira:RS-305}

h1. Intro

Various RS objects can be linked into free text (annotation text or forum post). The user can paste any [Data Basket|Data Basket Model] item using the editor toolbar, and we want to track all [Item Types|Data Basket Model#Item Types] except:
- Forum: forum post linking is handled by jForum
- Image: We currently don't have a display of image alone
- Text Snippet which: pasted itself, has no URI
- Web Link: represented as a normal URL in the text, doesn't need to be tracked
- Search: doesn't need to be tracked

h2. Link Types

Links are represented in text like this:
{code:html}
<a class="rslink linkMO" href="http://collection.britishmuseum.org/id/object/RFI41407">
RFI41407 Chromolithograph pictorial label used for...</a>
<a class="rslink linkStatement" href="http://www.researchspace.org/st/2">
amulet YCA70788 Glass two-finger amulet: this moulded funerary...: dimension</a>
{code}

|| Link Class || Item Type || Sample URL || Note ||
| linkMO | rso:FC70_Thing | [http://collection.britishmuseum.org/id/object/RFI41407] | Museum Object |
| linkStatement | rdf:Statement | [http://www.researchspace.org/st/2] | [Annotation Point|Annotation Design#Annotation Point] |
| linkDataAnnotation | rso:DataAnnotation | [http://collection.britishmuseum.org/id/object/RFI41407/annot/1] | [Data Annotaton|Open Annotation Collaboration (OAC)#Annotation with OAC and Reification] |
| linkImageAnnotation | rso:ImageAnnotation | [http://www.researchspace.org/DT219363.tif/annot/1] | [Image Annotation|Image Annotation Design#Example] |

h2. Annotations and Posts Linking an Object

In the first tab of a Museum Object (Object Details), we want to show all related annotations and forum posts. Related annotations/posts for an object are the ones that mention it, or one of its fields its fields.
!related_objects.png!

h2. Definition of Link

An annotation/post Links an object ?obj iff: there is an ?uri in the free-text such that:
|| Link to || Conditions || Notes ||
| object itself | ?uri a rso:FC70_Thing. ?uri=?obj |
| annotation point | {nf}?uri a rdf:Statement; dcterms:isPartOf ?obj{nf} | See [Open Annotation Collaboration (OAC)#Annotation with OAC and Reification|Open Annotation Collaboration (OAC)#Annotation with OAC and Reification] |
| data annotation | \{?uri a rso:DataAnnotation; oac:hasTarget ?obj} UNION \\
\{?uri a rso:DataAnnotation; oac:hasTarget ?st. ?st a rdf:Statement; dcterms:isPartOf ?obj} | See same |

h1. Link Data Model

Since Links are pasted from the Data Basket, they are similar to the [Bookmark Data Model|Data Basket Model#Bookmark]
| *Property* | *Notes* |
| rdf:type | rso:Link (new class) |
| oac:hasBody | oac:Body (for annotations) or rso:Forum (for a post)
- For annotation: points to the oac:Body of the annotation. The annotation text is stored in oac:hasBody/rso:P3_has_description.
- For forum post: they are stored in jForum, not OWLIM. We generate URIs like [http://www.researchspace.com/forum/123] (where 123 is the forum ID), and mark the URI with rso:Forum (new class) |
| oac:hasTarget | ?uri pointing to one of the [#Link Item Types] |
| rso:root | if ?uri matches one of the conditions in [#Definition of Link], the respective rso:FC70_Thing |

{warning}
This model links to oac:Body of annotation, with the idea that's most similar to forum, because the text is stored in the body.
The other option would be to link directly to annotation. Let me know if that's more convenient, and I'll rework the model{warning}

h2. Link Data Example

Here is a comprehensive example involving 3 links:
# Data annotation <object/123/annot/23> mentions <object/456>
# Forum post 321 mentions data annotation <object/456/annot/45> of <object/456>
# Image annotation <pic.tif/annot/67> mentions annotation point <st/56> of <object/456>

{noformat}
<link/1> a rso:Link;
oac:hasBody <object/123/annot/23/body>;
oac:hasTarget <object/456>;
rso:root <object/456>.

<forum/123> a rso:Forum;
<link/2> a rso:Link;
oac:hasBody <forum/123>;
oac:hasTarget <object/456/annot/45/body>;
rso:root <object/456>.

<link/3> a rso:Link;
oac:hasBody <pic.tif/annot/67/body>;
oac:hasTarget <st/56>;
rso:root <object/456>;
{noformat}
All these statements (including "a rso:Forum") need to be created

h2. Link Data Illustration

The figure above shows the same example, plus the extra statements that make the link to <object/456>.
!link-illustration.png!

h1. Link API

h2. Extract Links

- The annotation/forum text should be parsed to find all links (see patterns in [#Link Types])
- Each link is processed to find the linked object rso:root (see conditions in [#Definition of Link])
- If the link in text point to an Annotation Point (that is, it is "linkStatement"), then we need to load the rdf:Statement and get the object it is part of.

h2. Update Links

To implement this below for posts, we need to hook into the jForum API for create/update/delete.
- On *create* of annotation or post: extract and store the links.
Do this after the annotation/post is saved, so that we have the new annotation's URI
- On *edit* of annotation body or post: reparse and recreate the Links for that annotation/post
I.e. delete any existing links, extract and store new links
- On *delete* of annotation/post: delete the corresponding links


Links are stored using a method in the DMS2RDF class.

h2. Retrieve Links

There will be 2 methods in DMS2RDF:
{code:java}
URI[] getReferringAnnotations(URI uri):
// returns all annotation URIs that mention the MO with this uri or its annotation points
String[] getReferringForumPosts(URI uri):
// returns all forum posts that mention the MO with this uri or its annotation points
// IDs for the forum posts are returned as Strings.
{code}

{warning}Jana, don't you also need to list the data annotations of the object, even if they don't mention the object?{warning}