The WebL markup algebra is used for manipulating web pages and extracting data from them. Extracting information may range from simple operations like iterating all the links in a page to more complex operations that fill in Web forms and process the results returned from a server. Manipulating Web pages might involve rewriting parts of a page (for example highlighting words) or creating a new page from parts of several other ones.
The markup algebra consists of several operators and functions that operate on pages, tags, pieces and piece sets. There are operators and functions to create or build piece sets from pages or from other piece sets, convert pieces to their string representation, modify the content of a page, and so on.