Is it possible to know whether a textfile, e.g. in XML format, has been edited or tampered with over time?

The context to my question follows: 

I am a scientist in industry using a technology called 'mass spectrometry (MS)'.  MS is an analytical technique used, e.g. in forensic analysis to determine whether a particular compound is present in a sample (e.g. drug of abuse in blood or urine).

Mass spec. datafiles are usually stored in flat-file format to the instrument vendor's private binary specification - their software can process it, but nothing else can. However, open standards for MS data exist, and most vendors support export to at least one open specification. These open standards are mainly XML based these days (eg [mzML][1]) and allow processing with open source applications, and also allow long-term storage (> 10 years) of the data in a format that doesn't require that we maintain an archived computer and the OS (or VM) and the processing software for long periods.

The vendor binary format provides at least some security against data tampering, however the XML formats do not. Hence the issue - the open formats are very useful for providing access to data over archival timescales, but security is a problem.

  [1]: http://www.psidev.info/mzml_1_0_0%20