## 2 Case Studies
### Migrating Annotations across Multiple Representations of Museum Artefacts
* _Performance issues when Querying._ The complexity of the OA model may lead to slow performance when querying and retrieving on annotation fields that are buried a number of levels down the Annotation graph. For example, the most common query is on Targets e.g., \"give me all of the annotations on this Target resource\". The Target resource may be the object of the _hasTarget_ or _hasSource_ properties, or a selection that is retrieved by applying the _Selector_ to _hasSource_, or part of an _Aggregated Target_. Resolving all of these alternatives to match the Target URI and retrieve and display the relevant annotations, may require optimization to improve performance. * _Lack of standards for specifying segments of resources._ The ability to use segments or fragments of resources as Bodies or Targets, is extremely useful. However the interoperability of this aspect of the model is limited by a lack of standards across communities for describing/identifying parts of things e.g., text segments across document formats. The W3C Media Fragments Working group recently published a Proposed Recommendation which can be applied to multimedia resources (images, video, audio)--but there is a real need for communities to agree on schemas/mechanism for selectors on textual resources, maps, timelines and 3D objects. ## 5 Conclusions

In this paper we firstly describe the Open Annotation (OA) model that has recently been developed through the W3C Open Annotation Community Group by aligning the OAC and AO data models. We then apply this model to a number of use cases that have arisen within collaborative projects conducted through the UQ ITEE eResearch Lab. We have demonstrated how the OA model can be applied and extended in each use case, to support scholarly annotation practices ranging from basic attachment of comments and tags to digital resources, through to relating multiple target resources, and data annotation. We have also illustrated how the OA model has enabled us to create common backend infrastructure for storing, indexing and querying annotations across applications and authoring clients. We have identified and discussed some of the outstanding issues that need to be addressed in order to improve the interoperability capabilities of this approach. By exposing annotations to the Semantic Web as Linked Open Data, the Open Annotation approach enables robust machine-to-machine interactions and automated analysis, aggregation and reasoning over distributed annotations and annotated resources. Moreover, this annotation environment that will allow scholars and tool-builders to leverage traditional models of scholarly annotation, while simultaneously enabling the evolution of these models and tools to make the most of the potential offered by the Semantic Web and Linked Data environments. ## Acknowledgments

We gratefully acknowledge the contributions to this paper and to the annotation cases described within from the following individuals: [PERSON] and [PERSON] (scholarly editions); [PERSON] (3D museum objects); and [PERSON] (sensor data streams). We also wish to thank the Andrew W. Mellon Foundation for their generous funding of the OAC project and our collaborators from the Open Annotation Collaboration (in particular [PERSON], [PERSON], [PERSON]) and the W3C Open Annotation Community Group. ## References

* [PERSON] (2009) [PERSON] Collaborative semantic tagging and annotation systems. _Ann. Rev. Inf. Sci. Technol._**2009**, _43_, 187-239. * [PERSON] and [PERSON] (2011) [PERSON]; [PERSON] [PERSON] Open annotation: Beta data model guide. _Open Annot. Collab._**2011**. Available online: [[http://www.openannotation.org/spec/beta/](http://www.openannotation.org/spec/beta/)]([http://www.openannotation.org/spec/beta/](http://www.openannotation.org/spec/beta/)) (accessed on 12 April 2012). * [PERSON] et al. (2002) [PERSON]; [PERSON]; [PERSON]; [PERSON] Annotea: An open RDF infrastructure for shared Web annotations. _Comput. Netw._**2002**, _39_, 589-608.