====Lookup====

Lookups are very similar to [[enumeration|enumerations]] - they translate one value into something more human-readable.

The major difference between the two is the //number// of different values they support. Enumerations are suited to smaller, simpler sets of values - for example, having less than 10 distinct types of output text.

Lookups are different. When you define a lookup, you upload a **lookup table** containing the lookup value and the translation. This can have //hundreds// or even //thousands// of values.

This makes them very useful for looking up fault-codes and statuses in systems that share a single, large lookup table to translate those codes into meaningful messages.

===Table Format===

The lookup table should be in //tab-delimited// or //comma-separated// format, with the lookup value first and the displayed value second. The table should **not** include a header.

|0|OK|
|1|Starting|
|2|Running|
|3|Stopping|
|4|Stopped|
|10|No Air Pressure|
|11|No Power|
|12|Comms Lost|

===Performance Warning===

//Technical Section//

Why does ARDI have both an //enumeration// and a //lookup// type? The simple answer is **efficiency**.

When dealing with small numbers of options, it's quite easy to send the complete lookup table out to ARDI clients. When there are only a half-dozen options to choose from, the complete list is trivial to transmit.

However, when the list is significantly larger, it's puts a lot of load on the client and the network. Lookup properties instead push some of this additional work off to the driver, rather than loading-down the server and the client. 

Please use enumerations where possible, as a large number of small lookup properties will cause additional server load that will negatively impact performance.