Annotation validity using partial checksums

Abstract

Embodiments of the present invention generally provide a system, method and article of manufacture for validating annotations describing one or more portions of a data object. In general, prior to displaying a requested annotation, a current change detection value may be calculated from current data extracted from portions of the data object described by the annotation. The current change detection value may be compared to a previously saved change detection value calculated from data extracted from the portions of the data object at the time the annotation was generated. A mismatch in the current change detection value and the previously saved change detection value indicates a change in the annotated portions of the data object, which may render the annotation invalid. The annotated portions of the data object may be continuous or discontinuous.

1 . A computer-implemented method comprising: 
 creating an annotation for one or more portions of a data object;    calculating at least a first change detection value on data extracted from the one or more portions; and    creating an annotation record containing the first change detection value and the annotation.    
   
   
       2 . The method of  claim 1 , wherein calculating at least a first change detection value on data extracted from the one or more portions comprises calculating a separate change detection value for each of the one or more portions.  
   
   
       3 . The method of  claim 1 , wherein the one or more portions of the data object comprise discontinuous portions.  
   
   
       4 . The method of  claim 3 , further comprising: 
 extracting data from the one or more portions of the data object into a buffer; and    calculating the change detection value from the extracted data in the buffer.    
   
   
       5 . The method of  claim 4 , further comprising: 
 receiving a request for the annotation created for the one or more portions of the data object;    calculating a second change detection value on data extracted from the one or more portions after receiving the request for the annotation;    retrieving the first change detection value from the annotation record;    comparing the second change detection value to the first change detection value; and    providing an indication that the one or more portions of data have changed in response to determining the second change detection value and first change detection value do not match.    
   
   
       6 . The method of  claim 5 , wherein providing an indication that the one or more portions of data have changed comprises displaying an error message.  
   
   
       7 . The method of  claim 5 , wherein providing an indication that the one or more portions of data have changed comprises displaying the annotation and providing an indication the one or more portions of data described by the displayed annotation have changed.  
   
   
       8 . The method of  claim 7 , wherein providing an indication the one or more portions of data described by the displayed annotation have changed comprises at least one of: 
 changing an appearance of the displayed annotation or related text relative to an appearance of the displayed annotation or related text when displayed when the one or more portions of data have not changed; and    adding, removing, or changing a graphical icon.    
   
   
       9 . The method of  claim 1 , wherein the one or more portions of data comprise annotations.  
   
   
       10 . The method of  claim 9 , wherein calculating the first change detection value comprises retrieving change detection values calculated for data associated with the other annotations and calculating the first change detection value based on the retrieved change detection values.