Conversely, there may be numerous ways to transform the instance (possibly infinitely many), in which case a "best" choice of solutions has to be identified and justified.
[4] They have "evolved from being markup and display-oriented to further support the encoding of metadata that describes the structural attributes of the information.
For example, XML is a markup language that was designed to enable the creation of dialects (the definition of domain-specific sublanguages).
[citation needed] The following is a partial list of popular generic languages used for data exchange in multiple domains.
For example, XHTML has been defined as a format that is formal XML, but understood correctly by most (if not all) HTML parsers.
REBOL datatypes like URLs, emails, date and time values, tuples, strings, tags, etc.
The terms and relation types together can be used to create and interpret expressions of facts, knowledge, requirements and other information.