## 7 Future research directions  
For more extensive applications in industry, more in-depth work on annotations is necessary. The following describes suggested directions that the authors believe further work needs to focus on:  
1. _Persistent identification of geometry_: The issue of the persistent identification of geometry, also called the 'persistent naming problem', was raised by [PERSON] and [PERSON] [74]. The initial focus of the problem was how to identify the surviving entities of a pre-edit B-rep in the post-edit B-rep. Now, the persistent identification of geometry is becoming a key obstacle in translating annotations references between various 3D models formats, for example, how can annotations be shared among the users of the native CAD models and the users of the derived lightweight versions? To explore a solution, an experiment using UGS NX3 and Adobe Acrobat 3D 8.1 has been carried out [75]. The results show that the face labels in the original CAD model did survive during its translation to PRC format in PDF, meaning that all the faces of the product model could be persistently identified; it is therefore possible, at least in principle, that features based on a specific viewpoint could be constructed as combinations of the faces of the model. Correspondingly, if an original CAD model remains constant, the annotations could also survive within both the CAD model and the lightweight formats. Although the results are inspiring, there is a risk that the linkage between the CAD model and the annotation may be lost when the entity referred to is deleted in the CAD model. Obviously, an intensive exploration on the representations of 3D models and 3D annotation techniques needs to be carried out between academics, standards community and commercial industry.
2. _Semi-automatic/automatic information capture tools_: Most applications of annotation are still user-intervention-based. That is, it needs manual input. If the users forget to update their changes or neglect to retrieve the information to annotate, the annotation systems cannot work well and some of important information will be lost. Thus, dedicated information capture tools is worth exploring to support semi-automatic or automatic annotations. Some efforts on automatic information capture are being carried out by both academics and software industry. For example, the Simulation Process Studio (SPS) with UGS NX 3 Simulation [76] provides a palette of standard steps for users to drag and drop into the process with connecting lines defining the flow. The steps can then be saved as an XML file and made available to the standard Unigraphics NX application. Obviously, the results are still limited and more efforts are needed.
3. _Enhancement of support for development methodology_: As reviewed, recently, more and more researchers are transferring their attention to directly support design methodology, but the outputs of the work are still not enough. Further fundamental researches are required, including how to use annotation to help the capture of the design process, retrieval of rationale behind, and support of CAE tools. This would highlight that the work could be more meaningful if it integrates with latest design methodology and changes of working way (e.g. distributed cooperation). The latest work performed by [PERSON] _et al._[77] presented a general component-based approach to making records of transactional for design activities. In the proposed method, the activities are individually recorded in XML-based format, which can be assembled, tailored and transformed in different ways by XSL/XSLT. Therefore, it shifts design records to design reuse.