A computer-implemented method of indexing an object appearing in an image or a group of images, the method comprising: deriving a representation of the image or the group of images, by performing a derivation process for deriving a plurality of view descriptors of the object, each view descriptor corresponding to a different view of the object and comprising a representation of the shape of the object in the respective view, the derivation process comprising: a database indexer recognising one or more first views of the object as it appears in the image or group of images to derive one or more corresponding first view descriptors, based on a shape of the object in the one or more first views; and the database indexer selecting any additional views representative of the object to derive one or more corresponding additional view descriptors, the additional views of the object being views of the object that do not appear in the image or group of images, wherein the additional views representative of the object are selected from views of the object making up a complete or quasi-complete shape description of the object provided for use in indexing; and indicating for each view descriptor whether or not the respective view of the object corresponding to the view descriptor corresponds to a view of the object as it appears in said image or said group of images, by associating a flag with each view descriptor, including associating a first flag value with the one or more first descriptors and a second flag value of the flag with the one or more additional descriptors, the first value indicating the view is visible in said image or said group of images and the second value indicating the view is not visible in said image or said group of images. deriving a representation of the image or the group of images, by performing a derivation process for deriving a plurality of view descriptors of the object, each view descriptor corresponding to a different view of the object and comprising a representation of the shape of the object in the respective view, the derivation process comprising: a database indexer recognising one or more first views of the object as it appears in the image or group of images to derive one or more corresponding first view descriptors, based on a shape of the object in the one or more first views; and the database indexer selecting any additional views representative of the object to derive one or more corresponding additional view descriptors, the additional views of the object being views of the object that do not appear in the image or group of images, wherein the additional views representative of the object are selected from views of the object making up a complete or quasi-complete shape description of the object provided for use in indexing; and a database indexer recognising one or more first views of the object as it appears in the image or group of images to derive one or more corresponding first view descriptors, based on a shape of the object in the one or more first views; and the database indexer selecting any additional views representative of the object to derive one or more corresponding additional view descriptors, the additional views of the object being views of the object that do not appear in the image or group of images, wherein the additional views representative of the object are selected from views of the object making up a complete or quasi-complete shape description of the object provided for use in indexing; and indicating for each view descriptor whether or not the respective view of the object corresponding to the view descriptor corresponds to a view of the object as it appears in said image or said group of images, by associating a flag with each view descriptor, including associating a first flag value with the one or more first descriptors and a second flag value of the flag with the one or more additional descriptors, the first value indicating the view is visible in said image or said group of images and the second value indicating the view is not visible in said image or said group of images.