# Defining Alias MYALIAS.DAT

## What are Alias?

Alias are keywords that can be used instead of directory names. Whenever ENVI-met expects information about the location of a certain file, an alias can be used instead of typing the complete path to that file. In older versions, alias have already been used in ENVI-met to point for example to the default input (alias=[INPUT]) or the output (=[OUTPUT]) directory. From version 3.1 on, you are able to define your own list of alias.

When installing ENVI-met, you are asked to select a database folder. This is the place where you should store your simulation files. The alias for this default folder is [PROJECTS].
This is a system-internal folder and it is not stored in the MYALIAS.DAT file. If you need to change the location of the [PROJECTS] alias, you need to edit ENVIMET.ini in the ENVI-met program folder.

## What are the Benefits?

In former ENVI-met version, all of the directories used in a simulation had to be given in an explicit way.
If, for example, you have arranged your simulation input files in a folder called “c:\simulation\area1” you had to type this path each time a reference to input files is needed (e.g. the reference to the Area Input File given in the Configuration File).
If you decided to change the name of the folder or to re-organise your file, all these references had to be changed. Also, if you worked on different computers, you had to maintain the same directory structure on all computers in order to run the files without modifying them first.

Using the new alias concept, you define one or more individual alias for each simulation project and then just use the alias name in your configuration file. If you change the structure on your computer, you just have to update the alias definition and all the files keep working. If you use different computers, your directories can be stored wherever you want. You just have to take care of the alias definition file to point ENVI-met to the correct folders.

## How are Alias defined?

Alias are defined in the global file MYALIAS.DAT which is located in the \sys.basedata folder of ENVI-met. This file is loaded when ENVI-met is executed.If you change data in MYALIAS.DAT while ENVI-met is running, you have to update the data manually.
Also you have to re-load your configuration file if it uses one of the changed alias.

MYALIAS.DAT is a simple text file that can be opened and edited with any ASCII text editor. It might look like this:

 01: *[area1]=     c:\simulation\area1
02: *[trees]=     d:\envimet\trees_in_streets
03: [trees_out]=  [trees]\output
04: *[Co2]=       d:\envimet sim\CO2 impact
05: [co2_input]=  [co2]\input
06: [co2_output]= [co2]\output
(...)

Basically, you type in the alias you want to use in a project in square brackets “[..]” followed by “=” plus the path to the assigned folder. Although it is possible to assign folders located on other computers in a network there is a risk that file paths become unavailable during the simulation, so we do not recommend this method.

If you place a “*” in front of the alias, it will be treated as project alias (for example line 01). Project alias will be listed in the “Active Project” drop down box on the control panel of ENVI-met (see here). Selecting a project will automatically open the correct folder for selecting files.

Alias can be defined recursively. For example the alias [trees] is defined in line 02 and used to define another alias [trees_out] in line 03. The order of definition does not matter as long as all alias are resolved somewhere in MYALIAS.DAT.

You can define up to 50 different alias with up to 80 significant characters each (non case-sensitive). Three alias ([HOME], [INPUT] and [OUTPUT] are pre-defined in ENVI-met pointing to the system directory and to the default input and output folder.