meta-language tutorial [meta-metadata]

People use meta-metadata for different purposes. Librarians and information curators may author their own meta-metadata wrappers. Application developers may write their own programs in addition to authoring wrappers.

This tutorial is organized in 2 parts: wrapper authoring and compiling, and application development. The first part explains what you need to prepare for authoring new wrappers, the meta-metadata language, and how you integrate new wrappers with the system by compiling. The second part includes code examples for application developers to show how to use meta-metadata in your own programs.

Prior to authoring your own wrappers, you need to setup the environment using Java and Eclipse. You will author your own wrappers in Eclipse, in the form of XML files, and compile them into code in a target language (e.g. Java or C#) for use.

The core of the meta-metadata language is a cross-language type system that represents semantics in different systems and programming languages, with the support of S.IM.PL. With meta-metadata language, application developers, information curators, librarians, and power users author meta-metadata wrappers to specify data structure, extraction rules, semantic actions, presentation rules, and other aspects of semantics.

Follow the following pages through examples to learn how to write your own wrappers in meta-metadata language:

After authoring your own wrappers, you need to compile them into a target programming language, such as Java or C#, so that the meta-metadata and/or your application can use them. Remember that you need to setup the environment using Java and Eclipse to use the compiler.

MetaMetadata compiler compiles meta-metadata repository into metadata class declarations in a target programming language, with the same type hierarchy. The compilers themselves are written in Java, in the Java project simplTranslators, in the package ecologylab.semantics.compiler.

Currently, the entry class for the meta-metadata-to-Java compiler is
MetaMetadataJavaTranslator. For C#, the entry class is MetaMetadataDotNetTranslator.

For your convenience, two launch files have been added to the project:

Run CompileMmdToJava.launch to compile to Java.
Run CompileMmdToCSharp.launch to compile to C#.

You can launch these shortcuts from Eclipse by right clicking it and select Run, as shown below:

The compiler generates metadata class declarations in default locations:

For Java, it is the ecologylabGeneratedSemantics project.
For C#/.NET, it assumes that your workspace is in the same level with your Eclipse workspace, and with the name ecologylabSemantics.NET for the solution folder. (See environment setup for the recommended layout)

Code samples for application development in different target programming language are available to illustrate how to use meta-metadata with your own application.

For Java application developers, the following code samples are available in the ecologylabSemanticsExample project (listed with the entry class):

NewMmTest.java: A program that accepts a set of document URLs, and returns the extracted semantics in the form of serialized XML. This is a good starting point of how the meta-metadata system works, and makes a test case for testing your new wrapper.
NewWeatherDataCollector.java: A program that shows processing search results, collecting data from a weather forecast website, and storing results in a CSV format.
MetaSearch.java: A program that shows integrating semantics extracted from different sources and use them polymorphicly.

For C# application developers, the following code samples are available in the solution ecologylabSemantics.NET (listed with project name):

MmTest: A program that accepts a set of document URLs, and returns the extracted semantics in the form of serialized XML. This is a good starting point of how the meta-metadata system works, and makes a test case for testing your new wrapper.
MetaSearch: A program that shows integrating semantics extracted from different sources and use them polymorphicly.

The Objective-C code samples will come soon.