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You can't retrieve original time-series data from SAX storage because of normalization. To query time-series data by content (approximate 1-NN, motif discovery,
by chaotic-good 11y ago
You can't retrieve original time-series data from SAX storage because of normalization. To query time-series data by content (approximate 1-NN, motif discovery, etc) you need inverted index.
- cbsmith 11y agoThe normalized data is the index. It can still be pointing to the raw data. The nice thing is that the index organizes the data in a way that makes it easily (lossless) compressible.
- chaotic-good 11y ago> It can still be pointing to the raw data. Yep. Each SAX word should be mapped to the list of seriesid:timestamp pairs. This list is often referred as postings list in information retrieval. The resulting data-structure is an inverted index. SAX and iSAX papers describes inverted index variant (really bad one) based on folder structure but one can use convenient IR tools for this.
- cbsmith 11y agoiSAX2 yields a much better inverted index style model. The thing is, particularly with time series data, a lot of times it is sufficient to at least start with the summary data in the index.