I have reviewed this document as part of the Operational directorate's ongoing effort to review all IETF documents being processed by the IESG.  These comments were written with the intent of improving the operational aspects of the IETF drafts. Comments that are not addressed in last call may be included in AD reviews during the IESG review.  Document editors and WG chairs should treat these comments just like any other last call comments.   This document proposes a new iCalendar calendar component that allows the publication of available and unavailable time periods associated with a calendar user and further extends CalDAV calendar-access and calendar-auto-schedule to allow free-busy looksup to use the information from the new iCalendar availability components. I think this document is ready for publication. Here are a few editorial comments:   1.        Paragraph 4,5 of section 1: Is Update to RFC4791 required when you introduce an extension to CALDAV calendar-acess and CALDAV calendar-auto-schedule features? Can new iCalendar availability component work together with VERFY component? Or They are exclusive.   2 . Section 4 How VALAILABILITY component works together with VERYBUSY component? It looks the section 3 is about how one VAVAILABILITY component works together with another VAVAILABILITY component while the section 5 is about one VAVAILABILITY component works together with other component? Would you like to make this clear in the section title or in the texts of each section.   3. Last paragraph of section 4 Since the range for priority property value is {0,9~1}, spacing out method doesn’t looks scalable suppose you have 20 components that need to be ordered by priority.   Is there any default priority difference between two intersecting component with different priority value? In your example, it seems you choose 2?   4. The 3 rd paragraph of section 5 s/ first available time /first the available time   5.Example procedure in the section 5 Suggest to move all the example to one place .e.g., appendix A since it is hard to understand when some example snippet in one place and other example snippet in the appendix.   6. Section 5, step 2 of example procedure said: “ Append the "VAVAILABILITY" component to a list of components            for further processing in step 3, if it has not been ignored. ” Step 3 is confusing, since the example procedure has a third step, in the second step, there is also a 3rd step. Suggest change 4 steps in the step 2 into sub step such as step 2.1, step 2.2, step 2.3, step 2.4 Then you will clear the confusing step 3 in the step 2 with step 3 in the example procedure.   7. Section 5, the first paragraph said: “ In the examples below a table is used to represent time slots for the    period of a free-busy request. ” There are two tables in the section 5.1, which table are you referred to? I believe it is the second table, I would suggest to add a number and title for each table and then you can reference table number to clear the confusing introduced here.   8. Section 5.1.2 Would you like to generate a similar table as one in the section 5.1.1?   9. Section 7.1 said: “ "VAVAILABILITY" components are treated in a manner similar to    "VEVENT" and "VTODO" components, ” How VENET and VTDO component are treated? In which way? Can you provide a reference which discuss how VEVENT component is treated?   -Qin