Abstract: Methods and corresponding apparatuses for compressing, monitoring, decompressing or analyzing multidimensional data in a computer system. A sequence of multidimensional input data is received from a data generating process and is processed by using an approximation model to project respective blocks of input data on a subspace. For each block of data, a residual representing the difference between said data block and a reconstruction of the data block from the projection of the data block on said subspace is calculated. The calculated residual is stored in a repository while the projection of the data block is appended to previously stored projections of data blocks in an output buffer. The approximation model may be extended through analysis of the repository of residuals in order to detect significant patterns. If a significant pattern is found, the pattern may be added as an extension to the approximation model.