These are the XProc steps that a conformant XProc processor must support. In other words: whatever processor you use for processing your XProc pipelines, you can trust that these steps will always work.
A C D E F H I J L M N P R S T U W X
p:add-attribute - Add (or replace) an attribute on a set of elements.
p:add-xml-base - Add explicit xml:base attributes to a document.
p:archive - Perform operations on archive files.
p:archive-manifest - Create an XML manifest document describing the contents of an archive file.
p:cast-content-type - Changes the media type of a document.
p:compare - Compares documents for equality.
p:compress - Compresses a document.
p:count - Count the number of documents.
p:hash - Computes a hash code for a value.
p:http-request - Interact using HTTP (or related protocols).
p:identity - Copies the source to the result without modifications.
p:insert - Inserts one document into another.
p:json-join - Joins documents into a JSON array document.
p:json-merge - Joins documents into a JSON map document.
p:namespace-delete - Deletes namespaces from a document.
p:namespace-rename - Renames a namespace to a new URI.
p:set-attributes - Add (or replace) attributes on a set of elements.
p:set-properties - Sets or changes document-properties.
p:sink - Discards all source documents.
p:split-sequence - Splits a sequence of documents.
p:store - Stores a document.
p:string-replace - Replaces nodes with strings.
p:text-count - Counts the number of lines in a text document.
p:text-head - Returns lines from the beginning of a text document.
p:text-join - Concatenates text documents.
p:text-replace - Replace substrings in a text document.
p:text-sort - Sorts lines in a text document.
p:text-tail - Returns lines from the end of a text document.
p:unarchive - Extracts documents from an archive file.
p:uncompress - Uncompresses a document.
p:unwrap - Unwraps elements in a document.
p:uuid - Injects UUIDs into a document.
p:wrap - Wraps nodes in a parent element.
p:wrap-sequence - Wraps a sequence of documents in an element.
p:www-form-urldecode - Decode a URL parameter string into a map.
p:www-form-urlencode - Encode parameters into a URL string.
p:xinclude - Apply XInclude procesing to a document.
p:xquery - Invoke an XQuery query.
p:xslt - Invoke an XSLT stylesheet.