Cybersearch2

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Expression Pattern Language (eXPL)

Introduction » Getting Started

Download and Install eXPL Package

To get started with eXPL, you will need to download and install a Java package which contains the eXPL compilier, sources and examples. Step by step instructions follow.

Step 1 - Confirm software development readiness

See Java Tools table on right for links to download sites and descriptions, including minimum recommended versions. The Java SDK must also be installed on your PC. The suggested download is Java Platform (SDK) 8. If the Java SDK is already installed, then check it is version either 7 or 8 otherwise there may be compatibility problems.

The project is self-contained so all that is needed to examine and run the examples, post installation, is a text editor and a command console with the Java SDK included in the path. However, if you set up a project in a Java IDE, it makes getting started easier. Candidates include Eclipse, NetBeans, JDeveloper and IntelliJ IDEA.

The installation assumes Maven will run from the command line (eg. the command mvn --version should display information about Maven).

If you choose to go with Eclipse, more information can be found at Maven for Eclipse.

Step 2 - Download project to your PC

Download the eXPL project from the online Git repository, which can be performed from a command console. Go to, or create, a suitable workspace location and run:

git clone https://github.com/cybersearch2/eXPL.git

Upon completion, the project will be found in a newly created "eXPL" sub directory, which is referred to on this site as the eXPL "home location". There are two modules, parser, which is the eXPL parser and query engine and tutorial. which contains the code examples for the eXPL Reference.

Step 3 - Maven Build

To build the project and deploy artifacts to the local repository, go to the eXPL home location and run:

mvn clean install

Upon completion, the message "BUILD SUCCESS" should be displayed. If the build failed, then you will need to scroll back and investigate what error messages appeared during the build.

Running Examples

The eXPL project consists of 2 modules:

parser module, which compiles and builds the eXPL runtime library
tutorial module, which is divided into chapters containing examples linked to the Reference

How eXPL Queries are Run

Take a look at the source code for class HighCities in package au.com.cybersearch2.classy_logic.tutorial1 located in the main java sources of the tutorial module. HighCities is a small Java application with a main() static method. Here is the code to focus on:

/**
* Compiles the high_cities.xpl script and runs the "high_city" query
*/

public Iterator<Axiom> findHighCities() {

QueryProgram queryProgram =

queryProgramParser.loadScript("high_cities.xpl");

Result result = queryProgram.executeQuery("high_cities");
return result.getIterator("high_cities");

}

The findHighCities() method compiles an eXPL script named "high_cities.xpl". The assembled script is stored in a QueryProgram object. The query is then executed using it's name to identify it - ie.

queryProgram.executeQuery("high_cities")

The query result contains axioms and axiom lists, both identified by name.

Some things to note about the tutorial examples:

As stated on the previous page, tutorial examples are linked to the Reference which should be used to navigate the examples
The examples refer to resource files which are located in the main resources folder of the tutorial module.
The resource files mostly consist of eXPL files with "xpl" extension or copies of expected console output in ".lst" files
The comments will contain a description of what the example demonstrates, a copy of the eXPL script and what is the expected output to appear on the console

Java Tools

Tool	Description
java	Java SDK 8 is the current development platform but SDK 7 is compatible
git	Git is a free and open source distributed version control system.
maven	Apache Maven is a software project management and comprehension tool. Recommended version 3.5.0 and above
eclipse	Suggested Java integrated development - comes with plugins for Git and Maven. Version: Eclipse Neon.

The parser module creates a parser.jar file which must be in the classpath in order to compile and run the examples. The parser.jar file will be found in the target directory of the parser module following a successful build.

The tutorial module examples source code is contained in sub directory src/main/java. It is a good idea to compile the sources yourself so you are free to experiment. However, you will find that Maven also compiles the sources to target/classes

The examples must be launched from the tutorial directory in order for resource files to be located when they run. Here is an example of a command which runs the first example - all to be typed on the same line and having compiled the source to sub directory bin:

java -cp .:bin:../parser/target/parser.jar au/com/cybersearch2/classy_logic/tutorial1/HighCities

Note that the classpath separators shown here "/" (slash) and ":" (colon) are for Linux, while for Windows, they are "\" (back-slash) and ";" (semi-colon).

An easier approach to running tutorial examples is to import eXPL modules into a Java IDE with Maven plugins. Each example can then be run using "Run as Java application...".

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