Tags & Variables (The Differences)

[Darius1968]

I know that Tags are supposed to be faster in for instance, Data Driven Categories for the display and enumeration of data than are the variables.  I've made an honest attempt to read up on the data in the help file to understand what the differences are, but when I search  for the two terms, numerous entries are given, and I don't know where to start.  Can someone please tell me where in the help file I might look? 
Also, why the speed discrepancy?  Is it because tags are like the attributes in that they are already part of the IMatch database, and hence, available for quicker access, whereas the variables have to be first scraped out of the file? 
Finally, in the search function and in the filtering, are both, tags & variables, available for query?  So far, it seems that in the filtering of values, only the tags are available. 

[Mario]

Also, why the speed discrepancy?  Is it because tags are like the attributes in that they are already part of the IMatch database, and hence, available for quicker access, whereas the variables have to be first scraped out of the file? 

Data-driven categories are created and updated by the database engine. When it can use the original tag value stored inside the database, the entire operation is performed 'in' the database and thus much faster. In this specific case.

In general: Variables allow you to access and format file attributes, metadata, IMatch attributes and other data in every context IMatch allows the use of variables (file window, file window tip, Batch Processor, Renamer, Design & Print, App Panel, ...)

IMatch variables are a very flexible and powerful feature. But they come with a certain overhead. When you use a variable somewhere, IMatch has to perform a lot of work in the background to make all this work:

+ Read, parse and analyze the text to find the variable(s)
+ Retrieve the value of the variable (which may cause one or more database accesses)
+ Format the data according to standard variable formatting rules
+ If you have used variable formatting functions, execute these functions to modify the result of the variable
+ Convert the output again to text and 'use' it in whatever context you have used the variable

Variables are not available in the Filter panel. The filter panel accesses the database directly, and variables would have no benefit here.