Special properties provide alternative access method to Org mode features discussed in the previous chapters, like the TODO state or the priority of an entry. This interface exists so that you can include these states into columns view (see Column view), or to use them in queries. The following property names are special and should not be used as keys in the properties drawer:
TODO The TODO keyword of the entry.
TAGS The tags defined directly in the headline.
ALLTAGS All tags, including inherited ones.
PRIORITY The priority of the entry, a string with a single letter.
DEADLINE The deadline time string, without the angular brackets.
SCHEDULED The scheduling time stamp, without the angular brackets.
TIMESTAMP The first keyword-less time stamp in the entry.
TIMESTAMP_IA The first inactive time stamp in the entry.
CLOCKSUM The sum of CLOCK intervals in the subtree. org-clock-sum
must be run first to compute the values.