LexEVS 6.x Loader Use Guide

When first installed, LexEVS (an open-source, enterprise-wide terminology server) comes with no terminologies loaded into it. This documentation will cover the means for loading most content types that can be loaded. LexEVS was built to accommodate a wide variety of input and meld it into a common form - unifying many common source formats.

If you are interested in the underlying details about loading like the LexEVS information model, the loader code itself, and the framework used to create new loaders then you'll want to read the LexEVS 6.x Loader Guide.

The fact that there are many source formats necessitates a variety of LexEVS loaders, each used on a specific incoming source format. When we speak of these generically, inputs to be loaded are typically called terminologies or coding schemes. Each terminology will have a specific source format. For example, if you load the terminology called the "NCI Thesaurus" you will download a file in one of several source formats namely a text file (TXT), a Web Ontology Language file (OWL), or a LexGrid XML file (XML).

LexEVS provides both a LexEVS administrative GUI and LexEVS loader commands to load terminologies. While the LexEVS administrative GUI is very functional, a system administrator may prefer the command line interface because command scripts can be adjusted to increase memory and tune other java virtual machine settings to insure that loads of larger terminologies have adequate resources. For example, a user may select a loading script, open it in an editor, increase the java heap size and PermGen memory, depending on the machine’s resources, and save the script before running with the appropriate options written into the command line. Still, the GUI can be convenient for loading smaller terminologies and, in many cases, works fine for loading moderately large terminologies like the NCI Thesaurus. Loading terminologies requires some knowledge of the source format of the terminology.

Generic loading

Most terminology loads can be easily accomplished by pointing either the LexEVS commands or the LexEVS administrative GUI at the terminology source file and running the loader. Before you try this, you should look to see if the terminology you want to load is a special case (at the bottom of this page). Generic loading instructions can be found for the LexEVS administrative GUI or the LexEVS loader commands. For many source formats you can use a variation of the following LexEVS command:

Linux

./LoadOWL.sh -in "file:///ontologies/owl/amino-acid.owl"

Windows

LoadOWL.bat -in "file:///ontologies/owl/amino-acid.owl"

This LexEVS loader command loads input in OWL format. Substituting the matching LexEVS loader command for the source format being used and pointing the loader to a local file will load most terminologies. For example, the OBO source format would be loaded by the LoadOBO command. In the LexEVS administrative GUI, all of the various source format loaders are found under the "Load Terminology" menu. The administrative options must be enabled first in the Command menu.

Best Practices

As you work with terminologies in LexEVS there are some things that you will find are the best way to approach things to make life easy as far as loading goes.

Indexing terminologies

Loading any terminologies can be very time consuming and resource intensive and this can be helped by the following recommendations for database optimization.  This is more necessary the larger the terminology gets. The LexEVS configuration file, <LEXEVS_HOME>/resources/config/lbconfig.props, should be changed depending on how the primary key for the database should be generated. The default setting for the value of the database primary key is the following:

# DB_PRIMARY_KEY_STRATEGY indicates which strategy will be used
# for the primary key of the database tables.
# WARNING - This cannot be changed after the initial
# schema installation.
#
# Allowable values include:
#
#	"GUID"
#		- Primary Keys are implemented as random GUIDs.
#	"SEQUENTIAL_INTEGER"
#		- Primary Keys will be sequentially incremented
#		- as Ingeter values.
DB_PRIMARY_KEY_STRATEGY=GUID

Because this default is very taxing on the index processing at the end of the load, we recommend changing it to SEQUENTIAL_INTEGER for any terminology unless you have a priority need for Global Unique Identifiers. Note that this setting is final once any terminology is loaded. You can not change this after it is in effect. Even launching any LexEVS administrative command or opening the LexEVS administrative GUI will make this permanent. The only way to start over and change the setting is to change the lbconfig.props file, drop the database created for LexEVS, and recreate the database. If you are going to make the change this setting then do so before you do anything with LexEVS.

Database Connection setting for loading large terminologies

When large terminologies like NCI Metathesaurus is being loaded, the database connection might get suspended while waiting for the lucene indexing to complete. To mitigate this problem set the autoReconnect to true in the database URL in the lbconfig.props file. If it is MySQL, the URL would look like:

DB_URL=jdbc:mysql://bmidev4:3307/testLoad2010?autoReconnect=true

and you will have to restart MySQL database using following parameters:
--tmpdir /data/mysqltmp
--wait_timeout=100000

The tmpdir could be pointing to any directory but make sure it has enough space (in case NCI Metathesaurus, around 20Gb will be ideal). The --wait_timeout=100000 which is the number of seconds for 27 hours, will hold the connection for 27 hours.

Monitoring a load

While terminologies are being loaded, you can monitor the progress using the LexEVS logs (both 'load' and 'full' log) and if using MySQL, use INNODB tools to monitor Inserts per second. ( SHOW INNODB STATUS )

Setting a terminology as active

When you first load any terminology is is not active by default. One thing you must do is to activate it after it is loaded if you want any queries to work against it. The LexEVS Administrative GUI has a button to activate or deactivate any given terminology. All the LexEVS loader commands also have a flag that can set a terminology to be active upon successful load. The reason for having these states is that you can take terminologies offline without having to unload them.

Setting a terminology as the production terminology

It is best if you always tell LexEVS if a terminology is the default, even if you only have one copy of it loaded. Some queries, like queries to terminology metadata, do not work without setting a terminology as the production copy. You do this by tagging a terminology. The LexEVS Administrative GUI has a button to change the tag of any loaded terminology. The LexEVS loader commands have a flag that can be used to set the tag. The tag is a simple string. You can assign any tag you want, but the string recognized by LexEVS is "PRODUCTION" (all caps, no quotes). You should get in the habit of marking loaded terminologies as PRODUCTION. The opposite of that might be "TEST" or just left blank. The reason for having the tagging function is to allow for multiple versions of the same terminology to be loaded with no ill effect because one of them can be designated as the default with this approach.

Restarting distributed services after loading

After loading terminologies in a LexEVS Distributed environment you will not see any results of doing so until you restart the web container. This is a limitation of the LexEVS Distributed service. Get used to restarting the application server after loading any number of terminologies. You do not have to restart after each one.

Special Case Loading

Some terminologies are special cases and need special handling. Each of these has its own documentation: