1. A system for generating an entity data structure using breadcrumb information, the system comprising: a computing device associated with a search engine having one or more processors and one or more computer-readable storage media; and a data store coupled with the search engine, wherein the search engine: extracts a plurality of Web pages associated with a first Web domain; identifies hypertext markup language (HTML) source code for each Web page of the plurality of Web pages; using the HTML source code for the each Web page, determines breadcrumb information associated with the each Web page, the breadcrumb information comprising relationships between different breadcrumb elements of a breadcrumb trail associated with the each Web page; aggregates the breadcrumb information for the plurality of Web pages belonging to the first domain; using the aggregated breadcrumb information, generates a first entity data structure, the first entity data structure comprising structural relationships between different breadcrumb elements associated with the plurality of Web pages associated with the first Web domain; and augments the first entity data structure with information from at least a second entity data structure associated with at least a second Web domain different from the first Web domain, the information comprising structural relationships between different breadcrumb elements associated with a plurality of Web pages associated with the second Web domain.