charter: revised membership rules

* Remove expected target size
* Clarify that TSC member is not limited to core project maintainers
* Clarify that the TSC Chairperson is permitted to select delegates to run
  regular meetings.
* Clarify that the TSC may invite observers to meetings.
* Add an attendance rule for TSC membership.

TSC-Charter.md

@@ -36,18 +36,19 @@ approved by the Board.
 
 ## Section 4. Establishment of the TSC.  
 
-TSC memberships are not time-limited. There is no fixed size of the TSC.
-However, the expected target is between 6 and 12, to ensure adequate
-coverage of important areas of expertise, balanced with the ability to
-make decisions efficiently.
+TSC memberships are not time-limited. There is no maximum size of the TSC.
+The size is expected to vary in order to ensure adequate coverage of important
+areas of expertise, balanced with the ability to make decisions efficiently.
+The TSC must have at least three members.
 
 There is no specific set of requirements or qualifications for TSC
 membership beyond these rules. The TSC may add additional members to the
-TSC by a standard TSC motion and vote.  A TSC member may be removed from
-the TSC by voluntary resignation, or by a standard TSC motion.
+TSC by a standard TSC motion and vote. A TSC member may be removed from the
+TSC by voluntary resignation, by a standard TSC motion, or in accordance to the
+attendance rules described below.
 
-Changes to TSC membership should be posted in the agenda, and may be
-suggested as any other agenda item.
+Changes to TSC membership should be posted in the agenda, and may be suggested
+as any other agenda item.
 
 No more than one-fourth of the TSC members may be affiliated with the
 same employer. If removal or resignation of a TSC member, or a change of
@@ -56,14 +57,29 @@ one-fourth of the TSC membership shares an employer, then the situation
 must be immediately remedied by the resignation or removal of one or more
 TSC members affiliated with the over-represented employer(s).
 
-The TSC members shall consist of Maintainers from Core Projects as
-defined in the project lifecycle document and Section 7.
+The TSC membership shall include (but is not limited to) Maintainers from Core
+Projects as defined in the project lifecycle document and Section 7. The TSC
+may, at its discretion, invite new members to join the TSC who are not
+considered to be Maintainers from Core Projects.
+
+The TSC may, at its discretion, invite any number of non-voting observers to
+participate in TSC meetings.
 
 The TSC shall meet regularly using tools that enable participation by the
 community (e.g. weekly on a Google Hangout On Air, or through any other
 appropriate means selected by the TSC). The meeting shall be directed by
-the TSC Chairperson. Minutes or an appropriate recording shall be taken
-and made available to the community through accessible public postings.
+the TSC Chairperson. Responsibility for directing individual meetings may be
+delegated by the TSC Chairperson to any other TSC member. Minutes or an
+appropriate recording shall be taken and made available to the community
+through accessible public postings.
+
+In the case where an individual TSC member attends fewer than 20% of the
+regularly scheduled meetings held within a six month period, and does not
+proactively communicate with the TSC their intention not to attend those
+meetings, the member shall be asked to consider voluntarily resigning their
+membership. Should a member fail to attend 100% of the meetings within a one
+year period, the member shall be automatically removed from the TSC. In such
+cases, the member may ask to continue as an invited observer to TSC meetings.
 
 ## Section 5. Responsibilities of the TSC.