+ Atom Syndication Format is a standard for publishing web feeds a.k.a web syndication. + These feeds are usually consumed by a feed reeder that aggregates news from many websites and displays them in a uniform format. + The Atom feed is an XML with a list of recent news containing their titles, URLs and short annotations. + It also contains some metadata (website author, title etc.). +
+
+ Using this simple XQuery
+ This is similar operation to xmltable used in SQL databases.
+ It converts an XML tree structure to the relational form.
+ In our case, the output is still XML, but in a format that can be read by relpipe-in-xml.
+ All put together in a single shell script:
+
Will generate a table with web news:
+ +
+ For frequent usage we can create a script or funcrion called relpipe-in-atom
+ that reads Atom XML on STDIN and generates relational data on STDOUT.
+ And then do any of these:
+
+ There are several implementations of XQuery.
+ Galax is one of them.
+ XQilla or
+ BaseX are another ones (and support newer versions of the standard).
+ There are also XSLT processors like xsltproc.
+ BaseX can be used instead of Galax – we just replace
+ galax-run -context-item /dev/stdin with basex -i /dev/stdin.
+
+ Reading Atom feeds in a terminal might not be the best way to get news from a website, + but this simple example learns us how to convert arbitrary XML to relational data. + And of course, we can generate multiple relations from a single XML using a single XQuery script. + XQuery can be also used for operations like JOIN or UNION and for filtering and other transformations + as will be shown in further examples. +
+ +