10.4. Transforms and the Use of XPath

The raw data retrieved, based on the URI attribute in the Reference element or application context, is passed along through a pipeline of the Transforms, if any. The DigestMethod, which is effectively the last step in this pipeline, produces the DigestValue. See Figure 10-6. At each stage in the pipeline, the data can take one of two forms: a sequence of octets or an XPath node-set. Each Transform algorithm requires one of these forms as implicit input; the final DigestMethod requires an octet sequence for input.

Figure 10-6. The data pipeline

This process sounds straightforward, but some complexities arise. ...

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