text: Many visual recognition problems can be approached by counting instances. To determine whether an event is present in a long internet video, one could count how many frames seem to contain the activity. Classifying the activity of a group of people can be done by counting the actions of individual people. Encoding these cardinality relationships can reduce sensitivity to clutter, in the form of irrelevant frames or individuals not involved in a group activity. Learned parameters can encode how many instances tend to occur in a class of interest. To this end, this paper develops a powerful and flexible framework to infer any cardinality relation between latent labels in a multi-instance model. Hard or soft cardinality relations can be encoded to tackle diverse levels of ambiguity. Experiments on tasks such as human activity recognition, video event detection, and video summarization demonstrate the effectiveness of using cardinality relations for improving recognition results.
  @cite_14: We introduce a boosting framework for multiple instance learning (MIL) with varied aggregation of instances. In this framework, a diverse set of aggregation functions can be used to refine the notion of a positive bag for multiple instance learning. We investigate the effect of a wide range of orness in aggregation, using ordered weighted averaging. Thus, we obtain a new notion of a positive bag, which can represent different levels of ambiguity. We evaluate the performance of the proposed algorithm on popular MIL datasets. The experimental results show that this algorithm outperforms the standard MILBoost algorithm.
  @cite_20: Support vector machines (SVM) have been highly successful in many machine learning problems. Recently, it is also used for multi-instance (MI) learning by employing a kernel that is defined directly on the bags. As only the bags (but not the instances) have known labels, this MI kernel implicitly assumes all instances in the bag to be equally important. However, a fundamental property of MI learning is that not all instances in a positive bag necessarily belong to the positive class, and thus different instances in the same bag should have different contributions to the kernel. In this paper, we address this instance label ambiguity by using the method of marginalized kernels. It first assumes that all the instance labels are available and defines a label-dependent kernel on the instances. By integrating out the unknown instance labels, a marginalized kernel defined on the bags can then be obtained. A desirable property is that this kernel weights the instance pairs by the consistencies of their probabilistic instance labels. Experiments on both classification and regression data sets show that this marginalized MI kernel, when used in a standard SVM, performs consistently better than the original MI kernel. It also outperforms a number of traditional MI learning methods.
summary: Kernel methods for multiple instance learning include G "a 's @cite_14 MI-Kernel, which is obtained by summing up the instance kernels between all instance pairs of two bags. Hence, all instances of a bag contribute to bag classification equally, although they are not equally important in practice. To alleviate this problem, Kwok and Cheung @cite_20 proposed marginalized MI-Kernel. This kernel specifies the importance of an instance pair of two bags according to the consistency of their probabilistic instance labels. In our work, we also use the idea of marginalizing joint kernels, but we propose a unified framework to combine instance label inference and bag classification within a probabilistic graph-structured kernel.