Missing Sample Rate (optional element) raises error

[anss-sis]

SampleRate element (under Channel) is optional. For pre-digital channels there is no sample rate so the SIS writer did not write out the SampleRate element. The IRIS validator failed with this error:

[2021-11-18 17:02:29] [SEVERE] edu.iris.dmc.Application exitWithError: edu.iris.dmc.station.conditions.SampleRateCondition.evaluate(SampleRateCondition.java:41)
edu.iris.dmc.station.rules.Rule.execute(Rule.java:44)
edu.iris.dmc.station.RuleEngineService.executeAllRules(RuleEngineService.java:160)
edu.iris.dmc.station.RuleEngineService.executeAllRules(RuleEngineService.java:142)
edu.iris.dmc.station.RuleEngineService.executeAllRules(RuleEngineService.java:108)
edu.iris.dmc.station.RuleEngineService.executeAllRules(RuleEngineService.java:47)
edu.iris.dmc.Application.run(Application.java:183)
edu.iris.dmc.Application.run(Application.java:168)
edu.iris.dmc.Application.run(Application.java:147)
edu.iris.dmc.Application.main(Application.java:118)

Putting an empty value or None value are invalid as per the xml schema rules. So the following options are not possible:
None and

That means the only way to write it out is not have the element in the xml. Please update the code to accept this case.

Thanks,
Prabha

[jcrummey]

I created a new issue (#144) to address Rule 305 and using a value of 0 for Channel:SampleRate to characterize pre-digital channels. Using 0 seems preferred to omitting the Channel:SampleRate element. However, the validator should allow the omission (maybe with just a warning) since it is an optional element.