Update README.md

README.md

@@ -31,6 +31,29 @@ A Dataset and Analysis on Short-Term Temporal Shifts, AACL main conference 2022"
 a timestamp which distributes from September 2019 to August 2021.
 - Entity Types: `corperation`, `creative_work`, `event`, `group`, `location`, `product`, `person` 
 
+***PREPROCESSING:***
+We pre-process tweets before the annotation to normalize some artifacts, converting URLs into a special token `{{URL}}` and non-verified usernames into `{{USERNAME}}`.
+For verified usernames, we replace its display name with symbols `{@}`.
+For example, a tweet
+
+```
+Get the all-analog Classic Vinyl Edition
+of "Takin' Off" Album from @herbiehancock
+via @bluenoterecords link below: 
+http://bluenote.lnk.to/AlbumOfTheWeek
+```
+
+is transformed into the following text.
+```
+Get the all-analog Classic Vinyl Edition
+of "Takin' Off" Album from {@Herbie Hancock@}
+via {{USERNAME}} link below: {{URL}}
+```
+
+We ask annotators to ignore those special tokens but label the verified users' mentions.
+
+
+
 ## Dataset Structure
 
 ### Data Instances