[4] Such agents are not commonplace even now, but some of the ideas of Web 2.0, mashups and price comparison websites may be coming close.
In order for search-engine spiders to be able to rate the significance of pieces of text they find in HTML documents, and also for those creating mashups and other hybrids, as well as for more automated agents as they are developed, the semantic structures that exist in HTML need to be widely and uniformly applied to bring out the meaning of published information.
[5] HTML 5 introduced new semantic elements such as
In HTML 5, some of those elements, such as and , are still specified as their meaning has been clearly defined "as to be stylistically offset from the normal prose without conveying any extra importance".
One important restriction of this approach is that such markup based on element inclusion must meet the well-formedness conditions.
[11][12] A means of marking-up any arbitrary section of HTML would require a mechanism independent of the markup structure itself, such as XPointer.