[liblouis-liblouisxml] Re: Liblouis table header

  • From: James Teh <jamie@xxxxxxxxxxxx>
  • To: liblouis-liblouisxml@xxxxxxxxxxxxx
  • Date: Tue, 21 Oct 2014 14:19:24 +1000

Hi Bert,
As I've noted in the past, I'm very much in favour of something like this in principle. I like your proposal. It's probably the most versatile and extensible so far. However, it's always the tricky details that we never quite manage to iron out. 

I have two major concerns:
1. I don't think the concept of grade applies well to all braille codes. For example, grade 1 in English is uncontracted and grade 2 is contracted. I believe there are other languages where grade 1 is actually contracted. I think we need to come up with a concept that applies more universally; e.g. computer braille, uncontracted, contracted, special purpose. Of course, a given code might have more than one table in each category, so the "grade" concept might still be useful, but perhaps not as a primary means of searching.
2. Some tables cover multiple locales; e.g. UEB would probably specify multiple locales. Nothing in your proposal prohibits this, but it needs to be taken into account as far as searching goes.
3. Minor, subjective point: Can we have display_name or friendly_name instead of pretty_name? :)
4. It would certainly be good to take localisation of pretty/friendly/display names into account as you have suggested. This eliminates the need for every project to localise these itself (making for wasteful duplication of effort) as is currently the case. Going forward, one concern would be how to get these names localised. While NVDA and other projects have translators, these use more standard formats and have established workflows. We'd need to find some way to make it easy for existing translators to provide localised table names.
5. It's also worth noting that putting the localised names in the table file would mean a fairly significant (potentially 50+) number of key/value pairs in each table. Might this cause performance problems? 

Jamie

On 21/10/2014 12:49 AM, Bert Frees wrote:

Hi all,

I want to bring this subject up again because we've been discussing it so many
times and I think it's about time we finally do something. To recap, we need to
develop a header format that can contain metadata about the table, and an API
for extracting metadata and querying tables.

Greg's proposal with the single-line comment on the first line was a good
start. But I'd like to have something a bit more flexible/extensible. I have
worked out something and I'd like to have you guy's opinions and suggestions.

For my DAISY Pipeline 2 work I have been nurturing the idea of selecting
translators based on some kind of "translator query". The use case is quite the
same as we have here for liblouis. The syntax I am proposing for DAISY Pipeline
is inspired by CSS media queries. A query is basically a list of key-value pairs
or keywords. I'm not proposing to use exactly the same syntax for liblouis, but
I believe we need something similar/mappable.

Let's take Greg's example:

     #afr#1#Afrikaans Uncontracted#za#Afrikaans ongekontrakteerde

It consists of 5 metadata fields. 3 of them can be used for automatic table
selection. The two other are for pretty printing in graphical user
interfaces. Combining the two locale fields (language and country) into a single
tag, the corresponding CSS query would look like this:

     (locale:af-ZA) (grade:1)

The same key-value pairs could be put in liblouis table headers. I like the idea
of having the metadata in special comments, in order to assure backwards
compatibility of new tables with old library versions, and so that
implementations of the liblouis table format can choose whether or not they
support metadata.

A possible syntax could be `#+<KEY>: <value>`

     #+LOCALE: af-ZA
     #+GRADE: 1
     #+PRETTY_NAME: Afrikaans ongekontrakteerde
     #+PRETTY_NAME_EN: Afrikaans Uncontracted

(This is org-mode's syntax by the way.) The keywords would be
case-insensitive. Some keywords will be standard, such as LOCALE, GRADE and
PRETTY_NAME, but I wouldn't restrict the allowed keywords in any way, in order
to keep the system flexible.

The CSS query syntax also allows single keywords, without a value. For example:

     (ueb) (grade:2)

This could be reflected in a `#+TAGS` field with a list of space-separated
"tags":

     #+LOCALE: en-US
     #+GRADE: 2
     #+TAGS: ueb

I haven't really thought about the API yet. It would be nice if one could
provide a list of key-value pairs and/or single keywords, together with a table
path, and get a table name back. The keys could possibly be sorted by
importance, and the API could possibly return some kind of "matching quotient"
that indicates whether the table is a good match for the query or not.


Thoughts?
Bert
For a description of the software, to download it and links to
project pages go to http://www.abilitiessoft.com



--
James Teh
Executive Director, NV Access Limited
Ph +61 7 3149 3306
www.nvaccess.org
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SIP: jamie@xxxxxxxxxxxx
For a description of the software, to download it and links to
project pages go to http://www.abilitiessoft.com

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