Functionality and Behaviour of the GSE

The GSE has been built to search shapes within the DSW by using geometric criteria. In order to achieve this objective, descriptors able to capture the relevant features of the shapes have to be coupled with the methodologies implementing the appropriate comparison criteria. The GSE realizes this goal by storing both tools for the extraction of the shape descriptors as well as for their comparison.

In order to improve the efficiency of the system the main functionalities of the search engine have been split into two groups:

●	off-line functionalities: are responsible for the extraction and comparison of the shape descriptors

●	on-line functionalities: support the user during the search phase.

Offline functionalities

In general the extraction of a shape descriptor is a time consuming task. It can take from few seconds to some hours depending on the size of the shape model and/or the methodology used. For this reason an automatic mechanism for the off-line extraction of the descriptors has been implemented.

In particular when a new shape is inserted into the system, the mechanisms provided by the GSE allow the extraction of all the descriptors of the inserted shape with respect to the tools available in the system. Once the descriptors have been extracted they are stored in the database. Analogously when a new tool for the extraction of a descriptor is plugged into the system, the corresponding shape descriptor is extracted from each shape contained in the DSW. Also in this case the descriptors are stored into the core data component.

While the comparison between two shape descriptors is not time consuming, the repetition of this task for all descriptors stored into the system may cause a sensible delay by answering a query. For this reason an off-line functionality of the system produces all possible similarity values among the descriptors stored in the core data component. Also in this case, all the values are computed by the system when a new comparison tool is plugged in. Finally, computed values are stored into the database, in order to be indexed during the on-line interaction of the user with the system.

Online functionalities

The on-line functionalities of the GSE allow the user to interact with the system minimizing the delay in the query response. These functionalities define the behaviour of the user interfaces by allowing the user to formulate and execute queries and to obtain the correspondent result.

The two fields "Shape Descriptors" and "Comparison Methodologies" refers to the set of shape descriptors and comparison tools currently available in the system, while the field "Shape list" refers to the set of shapes that are available for the search.