Chapter 7: Equivalences and Internationalization (I18N)

This chapter may seem complex at first, but it is not so. You will see that it is very natural. In fact, you will think... Why have we not used it before?

The best way of working is to start with an example, and then we will go into the subject in a more formal way.

I18N. One example

Let's make a simple example. For example, an actress/actor document:

Actress (www.example.com/actress.stxt):
    Name: Sheyla Queen
    Birthday: 2/21/1979
    Filmography:
        Film:
            Title: The last thing
            Year: 1992
        Film:
            Title: Garden in red
            Year: 1993

The grammar is quite simple:

Node Definition: 
    Name: actor
    Alias: acress
    Type: NODE
    Child:
        Node: name 
        Num: 1
    Child:
        Node: birthday 
        Num: 1
    Child:
        Node: filmography 
        Num: 1
Node Definition:
    Name: filmography
    type: NODE
    Child:
        Node: film
        Num: +
Node Definition:
    Name: film
    Type: NODE
    Child:
        Type: title
        Num: 1
    Child:
        Type: year
        Num: 1
Node Definition:
    Name: name
    Type: TEXT
Node Definition:
    Name: birthday
    Type: TEXT
Node Definition:
    Name: title
    Type: TEXT
Node Definition:
    Name: year
    Type: TEXT

Now, let's imagine that we want the same information in Spanish, but instead of translating everything, we make a grammar that is almost the same, but with aliases in Spanish.

The grammar would be left like this:

Node Definition: 
    Name: actor
    Alias: acress
    Alias: actriz
    Type: NODE
    Child:
        Type: name 
        Num: 1
    Child:
        Type: birthday 
        Num: 1
    Child:
        Type: filmography 
        Num: 1
Node Definition:
    Name: filmography
    Alias: Filmografía
    type: NODE
    Child:
        Type: film
        Num: +
Node Definition:
    Name: film
    Alias: película
    Type: NODE
    Child:
        Type: title
        Num: 1
    Child:
        Type: year
        Num: 1
Node Definition:
    Name: name
    Alias: Nombre
    Type: TEXT
Node Definition:
    Name: birthday
    Alias: Fecha de nacimiento
    Type: TEXT
Node Definition:
    Name: title
    Alias: Título
    Type: TEXT
Node Definition:
    Name: year
    Alias: Año
    Type: TEXT

And the document could be like this:

Actriz (www.example.com/actress_es.stxt):
    Nombre: Sheyla Queen
    Fecha de nacimiento: 2/21/1979
    Filmografía:
        Película:
            Título: The last thing
            Año: 1992
        Película:
            Título: Garden in red
            Año: 1993

In addition, these documents have something in common:

Well, this is very important, because in order to translate from one to the other we only need to change to the compacted form, change the namespace, and... that's it! The document is exactly the same.

This is a case of equivalent grammars. We won’t talk about internationalization here, as we are looking for something even more generic than that. We are looking for connections between languages, and this is what the following sections will be about.

But what we just did is a very interesting application.

Equivalences (**)

Let's talk about connections that can be made between different grammars, and their potential transformations. Actually we could stretch this topic much more, but we're just going to reflect on it a little bit, and show certain things.

Equivalent grammars (**)

We say that two grammars are equivalent if any document has the same compacted form; with the exception of the namespace of the first node.

This is the previous internationalization example, where we had the compacted form be the same.

Otherwise, two grammars are equivalent if they have the same canonical names, and an equal child structure.

One of the advantages of this is that internationalization is almost direct, as we have seen in the previous section.

This is very useful, as we can say that the languages are virtually identical. This would let us make future transformations, and a whole series of very easily automated works.

Transformable (or convertible) grammars (**)

I think the definition is quite clear, it's like saying that it is like a subset of another larger language.

Another application might be for building bridges between different documents. We can create a type of document that serves as a transformer from one language to another. This would be done by combining the aliases from one with canonical names, so that the transformation would be almost direct.

Note: The compacted from this one can be read with the target namespace (in full), although it doesn’t have to be the other way around. It is like a form of inclusion.

One thought: transformables are an easy way of moving from one language to another. If this was XML, it would be like having an already implemented XSLT!

Extensions (**)

Extensions are like transformable grammars, but seen from the point of view of the destination grammar.

This tells us that A is an extension of B. What we do here is extend the functionality of B, but we allow compatibility the other way around. That is, if we have B documents, they can also be used.