Change number types like si:value from xs:double to xs:decimal

In the first version of the D-SI XML model xs:double was used as data type for numerical values due to its easy usage in software. We have now encountered first use-cases where the precision of xs:double (number of decimal places) is no more sufficient to provide accurate values, e.g.

• time measures in the nano second scale
• exact decimal values with fixed amount of decimal places

The idea is to replace the data type xs:double by xs:decimal which

• allows to write values in the same way as it was possible with xs:double
• and in addition allows arbitrary precision of decimal values and save decimal places at file I/O