| Code | Display | Definition | 
| number  | 
Number | 
Search parameter SHALL be a number (a whole number, or a decimal). | 
| date  | 
Date/DateTime | 
Search parameter is on a date/time. The date format is the standard XML format, though other formats may be supported. | 
| string  | 
String | 
Search parameter is a simple string, like a name part. Search is case-insensitive and accent-insensitive. May match just the start of a string. String parameters may contain spaces. | 
| token  | 
Token | 
Search parameter on a coded element or identifier. May be used to search through the text, display, code and code/codesystem (for codes) and label, system and key (for identifier). Its value is either a string or a pair of namespace and value, separated by a "|", depending on the modifier used. | 
| reference  | 
Reference | 
A reference to another resource (Reference or canonical). | 
| composite  | 
Composite | 
A composite search parameter that combines a search on two values together. | 
| quantity  | 
Quantity | 
A search parameter that searches on a quantity. | 
| uri  | 
URI | 
A search parameter that searches on a URI (RFC 3986). | 
| special  | 
Special | 
Special logic applies to this parameter per the description of the search parameter. |