The Data Store API was created to allow multiple Firefox OS apps, with potentially different data structures and storage mechanisms, to create, maintain and share the same data objects efficiently between one another. Each app can then import the data into its own local IndexedDB to index according to their specific query needs. This is not necessary however, and you can just write directly to the Data Store API data store.
The <integer>CSS data type denotes an integer number, positive or negative. There isn't any associated unit with the value. An integer consists of one or several decimal digits, 0 to 9, optionally preceded by one single + or - sign.
The <length>CSS data type denotes distance measurements. It is a <number> immediately followed by a length unit (px, em, pc, in, mm, …). Like for any CSS dimension, there is no space between the unit literal and the number. The length unit is optional after the <number>0.
The <percentage>CSS data types represent a percentage value. Many CSS properties can take percentage values, often to define sizes in terms of parent objects. Percentages are formed by a <number> immediately followed by the percentage sign %. Just as is the case with all other units in CSS, there isn't a space between the '%' and the number.
The <ratio>CSS data type, used for describing aspect ratios in media queries, denotes the proportion between two unitless values. It is a strictly positive <integer> followed by a slash ('/', Unicode U+002F SOLIDUS) and a second strictly positive <integer>. There may be spaces before and after the solidus.
The <resolution>CSS data types, used in media queries, denotes the density of pixels of an output device, its resolution. It is a <number> immediately followed by a unit of resolution (dpi, dpcm, ...). Like for any CSS dimension, there is no space between the unit literal and the number.
The <string>CSS data type represents a string. It is formed by a Unicode characters delimited by either double (") or single (') quotes. A double quoted string cannot contain double quotes unless escaped using a backslash (\). The same practice applies for single quoted strings, they cannot contain single quotes unless escaped using a backslash (\). The backslash character must be escaped to be part of the string.
The DataStoreChangeEvent interface of the Data Store API represents the event related to a record changed in the data store, i.e. this is returned once a change is made and the change event is fired (see DataStore.onchange for the handler).
The DataStoreCursor interface of the Data Store API represents a cursor that allows apps to iterate through a list of DataStoreTask objects representing the change history of the data store, for use when synchronizing the data.