The Canonical Text Services URN (CTS URN) scheme defined in the CTS URN specification closely follows the syntactic requirements of a URN, but extends its goal to provide a system of persistent, technology-independent identifiers for texts and passages of texts.
CTS URNs are built out of 5 components that are divided by a colon ":". urn:cts:[NAMESPACE]:[WORK]:[PASSAGE] urn:cts: defines this as a URN of the CTS protocol. [NAMESPACE] is the name(space) of a data set. [WORK] consists of a maximum of 4 parts that are divided by a dot and specifies the edition or document that is referred to. [PASSAGE] specifies the text part in the document.
Several special characters are not allowed to be used as descriptive parts in the URN, like . : @ [ ] because they are reserved for functional use. A complete list of reserved characters can be found in the CTS URN specification.
Text span (From one text part to another)
Sub passage notation