Dear Working Group II,
At the 2017 FDSN meeting in Kobe a number of extensions were approved to the StationXML 1.0 schema as listed in the meeting summary (http://www.fdsn.org/media/wg/II/2017/FDSN%20Working%20Group%202%20Meeting%202017%20-%20Summary-2.pdf
These changes have been incorporated into the StationXML 1.1 release candidate available here:
Additionally, a number of backwards-compatible changes suggested at previous meetings and on the project site were incorporated. Conforming to the versioning rules, all 1.0 version documents are also compliant with schema version 1.1, with one exception: the <StorageFormat> element was removed from the schema, but is not widely used and not expected to cause incompatibility.
All changes from version 1.0 can be see in this comparison:
On acceptance, a change log will be added to the repository that includes the accepted changes 
The additional changes have been reviewed and approved by EIDA and IRIS internally. As these are backwards compatible additions, we do not anticipate significant issues for implementors or users.
If no significant objections are raised by May 3rd, theses changes will be considered accepted and the new 1.1 schema will be posted to the FDSN web site.
Once this is completed, we will start a process to gather ideas for a major release of StationXML, which will be one of the major agenda items at the WG II meeting in Montreal. A proposed agenda for this meeting will follow shortly.
John and Chad.
* Add (persistent) <Identifier> element to all base nodes (Network, Station, Channel)
* [Partial] Unify response elements, allow "number" attribute to <Numerator> and <Denominator>
Comment: The incompatible portion is deferred to the next major version, specifically renaming the "i" attribute of FIRType to "number".
* Allow <CreationDate> to be optional
* Use xs:double for <ApproximationLowerBound>, <ApproximationUpperBound> and <MaximumError>
* Include data availability elements described in the fdsn-station+availability-1.0.xsd extension schema as options elements of the main schema
* Remove <StorageFormat> from <Channel>
* Limit each <Operator> to a single <Agency>
* Allow more than a single <Equipment> occurrences in <Channel>, same as in <Station>
* Allow <Operator> at the <Network> level, same as in <Station>
* Add "sourceID" attribute, with URI value, to the base node type for <Network>,<Station>,<Channel>
* Do not require and disallow <StageGain> for <Polynomial> response stages
* Add "measurementMethod" attribute to uncertaintyDouble attribute group
used by azimuth, dip, distance, latitude, longitude, elevation, etc. types
* Add <WaterLevel> and within <Station> and <Channel>
In two changes:
* Add "subject" attribute to <Comment> to allow relating comments, make "id" attribute optional.
The following issue was approved by the working group but is incompatible with the 1.0 schema and has been deferred to the next major revision:
* Force UTC times in the StationXML being marked as UTC
Mailing list discussion: http://www.fdsn.org/message-center/thread/464/