Simple query functions

[nuest]

• SOS object behaves like a data.frame with subsetting in "dimensions" offering, phenomenon, procedure, and time (space to complex)
• getData(...)
• download.sos(...)
• related ideas for convenience functions
  • sosTimeseries() - if no paramer is given, this function creates a list of time series based on capabilities document for all technically possible combinations of offering/foi/phenomenon/procedure. The elements of the returned list are properly formatted so that they can be used as input for the function like sosReadTimeseries(sosTimeseries(mysos)[[1]], time = "2010/02/01::2010/02/05"). This functions exploits the next idea:
  • sosMatching(offering, procedure, observedProperty, foi) - returns a list of possible matching elements, the parameters can be boolean or character, so that I can use the function to "get all procedures that observe property X" with sosMatching(procedure = TRUE, observedProperty="X"), or "get all foi that are in offering X and are observed by procedure Y" with sosAllForGiven(foi = TRUE, procedure = "Y", offering = "X").

[nuest]

Similar to sensorweb4R, these methods could also be named fetchMetadata(...) and fetchData(..). Could even change that creating a new SOS object actually does not request anything, but fetchMetadata does a GetCapabilities.

[nuest]

Replaced with #101 #100 #99 #98 #97 #96 #95 #94 #93 #92 #91 #89 #88 #87 #86 #85 #84 #83 #82 and #81