Sequencing technologies produce larger and larger collections of biosequences that have to be stored in compressed indices supporting fast search operations. Many compressed indices are based on the Burrows–Wheeler Transform (BWT) and the longest common prefix (LCP) array. Because of the sheer size of the input it is important to build these data structures in external memory and time using in the best possible way the available RAM. We propose a space-efficient algorithm to compute the BWT and LCP array for a collection of sequences in the external or semi-external memory setting. Our algorithm splits the input collection into subcollections sufficiently small that it can compute their BWT in RAM using an optimal linear time algorithm. Next, it merges the partial BWTs in external or semi-external memory and in the process it also computes the LCP values. Our algorithm can be modified to output two additional arrays that, combined with the BWT and LCP array, provide simple, scan-based, external memory algorithms for three well known problems in bioinformatics: the computation of maximal repeats, the all pairs suffix–prefix overlaps, and the construction of succinct de Bruijn graphs. We prove that our algorithm performs $${\mathcal {O}}(n\, \mathsf {maxlcp})$$ sequential I/Os, where n is the total length of the collection and $$\mathsf {maxlcp}$$ is the maximum LCP value. The experimental results show that our algorithm is only slightly slower than the state of the art for short sequences but it is up to 40 times faster for longer sequences or when the available RAM is at least equal to the size of the input.

The digital music revolution has improved the availability of music and made it easier to enjoy. The shift from hard support, such as audio CDs, to software leaves some unsatisfied by the loss of additional media contents, such as images, lyrics, and CD cover. We propose to fill the gap by enriching e-music with multimedia contents. Our proposal focuses specifically on MP3 as a widely distributed open format. The challenge we meet in enriching MP3 lies in maintaining audio compatibility and avoiding file size explosion. To this end, we define a description language to express multimedia contents in a textual way, with higher representation efficiency than existing languages. We also address security issues that arise from the use of an open format. Effectiveness is shown with an MP3 player capable of rendering multimedia contents.

This work proposes an approach based on dynamic Bayesian networks to support the cybersecurity analysis of network-based controllers in distributed energy plants. We built a system model that exploits real world context information from both information and operational technology environments in the energy infrastructure, and we use it to demonstrate the value of security evidence for time-driven predictive and diagnostic analyses. The innovative contribution of this work is in the methodology capability of capturing the causal and temporal dependencies involved in the assessment of security threats, and in the introduction of security analytics supporting the configuration of anomaly detection platforms for digital energy infrastructures.