The classification-item element must at least have a symbol. All other elements are optional Note the classification element is contained within itself. This is a recursive method to create a 'tree' structure of classifications A CPC symbol made up of the following consituent parts, constrained by the cpc-symbol-type SECTION: Sections are the highest level of hierarchy of the IPC Classification. Each section is designated by one of the capital letters 'A' through 'H' as recommended in WIPO Standard ST.8, with the addition of section 'Y'. CLASS: Each section is subdivided into classes which are the second hierarchical level of the IPC Classification. Each class symbol consists of the section symbol followed by a two-digit number as recommended in WIPO standard ST.8. SUBCLASS: Each class comprises one or more subclasses which are the third hierarchical level of the IPC Classification. Each subclass symbol consists of the class symbol followed by a capital letter from 'A' to 'Z' as recommended in WIPO Standard ST.8. MAINGROUP: Main Group consists of one- to four-digit number (1 to 9999) as recommended in WIPO Standard ST.8. This field can be blank, if classification level is 'S' (classification in subclasses only) SUBGROUP: Subgroups form subdivisions under the main groups the IPC Classification. Each subgroup consists of two- to six-digit number (00 to 999999) as recommended in WIPO Standard ST.8. This field can be blank, if classification level is 'S' (classification in subclasses only). The element meta-data' is used specifically by the OPS team to allow technical information (meta-data) to be communicated to consumers of this XML. Note Element. Notes are made up of note parts which can have note sub parts. Each note sub part can have it's own note part forming a tree structure of notes. A list of classifications transferred to other classifications along with the date of transfer A list of transferred from and transferred to classifications. For each classification we have a boolean attribute to define the use of subgroups HTML markup potentially contained within elements such as title, warning and notes etc. An element to encapsulate a cross referenced classification symbol Simple type describing a list of schemes