5. How does the OxGarage work:
The program is divided into 8 parts: API, framework, 4 plug-ins (1 validator, 3 converters), web service and web client. API offers only the base, on which the framework is built. The role of the framework is to search for all provided plug-ins, initialize them and calculate all possible input types and conversion paths. To do this, it asks each converter to provide a list of all conversions it is able to do. Then the framework constructs a graph, where different document types are nodes and conversions are edges. This graph is directed and weighted. Weights to the edges are assigned based on a subjective judgement of how good or bad the resulting document looks. The better the document looks, the lower the weight. These weights are then summed together and only the path with minimal total weight is offered to the user in case there are several routes available from input format to output format. Framework also provides for processing the path of conversions that are needed to be done and performing the necessary conversions in a chain of threads, where one thread passes its result to the next thread until the desired output format is reached. Each thread does exactly one conversion and uses a converter to perform it.
The role of validator is to validate documents before conversions. This is done in order to stop user from transforming a malformed document, as this could cause an error during conversion, or an unexpected result. Unfortunately, the validator is only capable of validating very few document formats (some XML documents) and hence it is not used very often.
Then there are converters, which do the conversion from one format to another. Each converter must be able to provide a list of all possible conversions it can do and also perform a conversion. Currently there are 3 different converters: XslConverter, TEIConverter and OOConverter. XslConverter and TEIConverter are using xsl style-sheets to convert between different form of XML documents. The main difference between them is that TEIConverter is used for a more complex conversions, e.g. conversions to and from docx and odt. The OOConverter is using a JODConverter library to start OpenOffice.org in a headless mode and then calls it to convert a document. More plug-ins (both converters and validators) can be added quite easily. If you are interested in this, I suggest reading http://enrich-ege.sourceforge.net/creation.html.
Web service is a servlet, that uses the framework to perform conversions. It is REST-full and you can control it simply using POST and GET request. First you need to send GET request asking for all the possible input formats. Then you need to send another GET request to get all possible output formats from a given input format. After this, you need to POST your file into a given URL and that's it. This can be particularly useful for batch processing a large number of files. For more information read http://enrich-ege.sourceforge.net/restws.html. Of course, if you already know the URL for the conversion, it is enough to POST your file to this URL without having to go through all these steps.
The last important part of OxGarage is the web client. This is basically a user interface for the web service. The important thing about it is that it requires JavaScript to work. This web client simply sends GET and POST requests to web service and processes the responses.
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