Abstract
XML is becoming the most relevant for data representation and exchange on the WWw. Novel languages for extracting and restructuring the XML content have been proposed, some in the tradition of database query languages (i.e. SQL, OQL), other more closely inspired by XML. This paper presents a comparison of XML algebra models and highlighting their common features and differences. The XML algebra models such as semi-structured algebra, IBM, Niagara, YATL, Lore, AT&T, W3C and TA