# How modularization of schema interacts with XJC

Over time schema authors have developed several techniques to modularize large schemas. Some of those techniques have some noteworthy interactions with XJC.

## Chameleon schema

Chameleon schema" (read more, in particular this) is a technique used to define multiple almost-identical sets of definitions into multiple namespaces from a single schema document.

For example, with this technique, you can write just one "foo" complex type and define it into namespace X and Y. In this case, one tends to hope that XJC will only give you one `Foo` class for this, but unfortunately because it's actually defined in two namespaces, JAXB needs two Java classes to distinguish `X:foo` and `Y:foo`, so you'll get multiple copies.

If you find this to be problematic, there are a few ways to work around the problem.

1. If you are in control of the schema, see if you can rewrite the schema to avoid using this technique. In some cases, the schema doesn't actually exploit the additional power of this technique, so this translation can be done without affecting XML instance documents. In some other cases, the chameleon schema can be argued as a bad schema design, as it duplicates definitions in many places.

2. If you are not in control of the schema, see if you can rewrite the schema nevertheless. This will only work if your transformation doesn't affect XML instance documents.

3. Perhaps there can be a plugin that eases the pain of this, such as by defining common interfaces among copies.