  MirBot is a collaborative application for smartphones that allows users to
perform object recognition. This app can be used to take a photograph of an
object, select the region of interest and obtain the most likely class (dog,
chair, etc.) by means of similarity search using features extracted from a
convolutional neural network (CNN). The answers provided by the system can be
validated by the user so as to improve the results for future queries. All the
images are stored together with a series of metadata, thus enabling a
multimodal incremental dataset labeled with synset identifiers from the WordNet
ontology. This dataset grows continuously thanks to the users' feedback, and is
publicly available for research. This work details the MirBot object
recognition system, analyzes the statistics gathered after more than four years
of usage, describes the image classification methodology, and performs an
exhaustive evaluation using handcrafted features, convolutional neural codes
and different transfer learning techniques. After comparing various models and
transformation methods, the results show that the CNN features maintain the
accuracy of MirBot constant over time, despite the increasing number of new
classes. The app is freely available at the Apple and Google Play stores.
