Relation?

[Sifting-Sand]

Is WML at all like working with XML?

[Ken_Oh]

Yes. For more info: http://wiki.wesnoth.org/ReferenceWML and http://wiki.wesnoth.org/Create

[pauxlo]

More detailed here: SyntaxWML.

Similarities:

• In WML we have "tags", which correspond to "elements" in XML. (I think there was a naming confusion when this was created.)
• Tags in WML may have subtags (any number, also multiple of each name), like elements in XML may have subelements.
• Tags in WML (and elements in XML) can have attributes, which are simple name-value-pairs (of Strings).
• There can be only one attribute of each name inside each tag/element. The ordering of attributes does not matter.
• Ordering of subtags/subelements may or may not matter, depending on the actual use case.

Differences:

• In WML the attributes are listed between the starting- and ending indicators, in XML inside the starting tag of an element.
• In WML you may note several attributes together as a list: x,y=20,40. This is not possible in XML.
• In WML attribute values you can concatenate multiple strings with +.
• In XML there may be text content inside a element, in WML is no "text content" inside of tags.
• There are no entity references (&) in WML.
• Most visible: WML uses square brackets [], XML uses angle ones <>.
• comments start in WML with # and go to the end of line, comments in XML start with <!-- and go to -->.
• XML may be encoded using different character sets, WML supports only UTF-8.
• XML can have a document type declaration, WML not (it implicitely is "WML like Wesnoth understands it").
• WML has a "tag continuation" with [+tag] ... [/tag], which adds the content to the last closed tag which same name. There is no such thing in XML.
• WML has a preprocessor (providing conditionals and macro replacement), which XML does not have.
• In XML, all attribute values should be in quotation marks ("...") - in WML these are optional (mainly used for line-continuations or strings containing a +). Additionally WML has "stronger quotes" with << ... >>, inside of which the preprocessor does not do anything. (This is mentioned only on LuaWML, I hope it works also at other places. Please correct me if this is wrong.)
• WML has an attribute translation feature: when you prefix an attribute value with _, it may be translated (support depends on context).
• (The SyntaxWML page mentions variables with $varname, but I think this is actually not part of the WML syntax, but only used at later stages of the interpretation, and only in some contexts (events and similar)).