We need to automatically process some printed Hausa documents and so I have several questions regarding the use of “hooked” ‘b’, ‘d’, and ‘k’ characters in printed Hausa:
1. How often are they used in printed Hausa texts? We have a collection of texts some of which contain these characters while others have none. Does this mean that these characters are optional and that the reader can deduce from context whether a given printed word with, say, a regular ‘k’, is in fact a word with a hooked ‘k’? How much context around a word that needs to be disambiguated does a reader need to do the disambiguation correctly?
2. Related to #1: given a word with one of more special characters, how likely is it that if all the special characters get replaced by their regular versions (hooked ‘k’ replaced by ‘k’ etc), the result will be a DIFFERENT word?
3. If the use of these characters is optional, are there certain genre of documents where they are used (or not used), such as official documents, newsprint, fiction literature etc?
4. Are there any books or online resources that describe the written rules for the hooked characters?

Thank you very much!