The main forum for communication on Moses is the Moses support mailing list.
We'd like to hear what you want from Moses. We can't promise to implement the suggestions, but they can be used as input into research and student projects, as well as Marathon projects. If you have a suggestion/wish for
a new feature or improvement, then either report them via the issue tracker, contact the mailing list or drop Barry or Hieu a line (addresses on the mailing list page).
Moses is an open source project that is at home in the academic research community. There are several venues where this community gathers, such as:
Moses is being developed as a reference implementation of state-of-the-art methods in statistical machine translation. Extending this implementation may be the subject of undergraduate or graduate theses, or class projects. Typically, developers extend functionality that they required for their projects, or to explore novel methods. Let us know if you made an improvement, no matter how minor. Also let us know if you found or fixed a bug.
We are aware of some commercial deployments of Moses, for instance as described by TAUS. Please let us know if you use Moses commercially. Do not hesitate to contact the core developers of Moses. They are willing to answer questions and may be even available for consulting services.
If you are looking for projects to improve Moses, please consider the following list:
- Out-of-Vocabulary (OOV) Word Handing: Currently there are two choices for OOVs - pass them through or drop them. Often neither is appropriate and Moses lacks good hooks to add new OOV strategies, and lacks alternative strategies.
A new phrase-table class should be created which process OOV. To create a new phrase-table type, make a copy of
Rename the class and follow the example in the file to implement your own code
- Incremental updating of translation and language model: When you add new sentences to the training data, you don't want to re-run the whole training pipeline (do you?). Abby Levenberg has implemented incremental training for Moses but what it lacks is a nice How-To guide.
- Faster tuning by reuse: In tuning, you constantly re-decode the same set of sentences and this can be very time-consuming. What if you could reuse part of the calculation each time? This has been previously proposed as a marathon project
- Use binary files to speed up phrase scoring: Phrase-extraction and scoring involves a lot of processing of text files which is inefficient in both time and disk usage. Using binary files and vocabulary ids has the potential to make training more efficient, although more opaque.
- Lattice training: At the moment lattices can be used for decoding, and also for MERT but they can't be used in training. It would be pretty cool if they could be used for training, but this is far from trivial.
- Decoding algorithms for syntax-based models: Moses generally supports a large set of grammar types. For some of these (for instance ones with source syntax, or a very large set of non-terminals), the implemented CKY decoding algorithm is not optimal. Implementing search algorithms for dedicated models, or just to explore alternatives, would be of great interest.
- Cube pruning for factored models: Complex factored models with multiple translation and generation steps push the limits of the current factored model implementation which exhaustively computes all translations options up front. Using ideas from cube pruning (sorting the most likely rules and partial translation options) may be the basis for more efficient factored model decoding.
- Missing features for chart decoder: a number of features are missing for the chart decoder, such as: MBR decoding (should be simple) and lattice decodings. In general, reporting and analysis within experiment.perl could be improved.
- More efficient rule table for chart decoder: The in-memory rule table for the hierarchical decoder loads very slowly and uses a lot of RAM. A optimized implementation that is vastly more efficient on both fronts should be feasible.
- Only maintain total hypothesis weight in decoding: At the moment, each hypothesis (partial translation) contains the full feature vector, but really all that is required is the weighted score. The feature vectors could then be supplied lazily, if needed for n-best lists, and decoding would be more efficient.
- Scope-0 grammar and phrase-table (Hieu Hoang). The scoped of a grammar is a measure of the ambiguity when applying the grammar to an input sentence. (See this paper for more details:)
If the scope is 0, there is no ambiguity. It would be good to know if this restriction hurts translation quality a lot, or if it improves translation.
Also, the phrase-table lookup for a Scope-0 grammar can be significantly simplified, made faster, and applied to much large span width. Another project would be to rewrite the phrase table lookup and parsing algorithm specifically to deal with Scope-0 grammar.
- Faster training for the global lexicon model: Moses implements the global lexicon model proposed by Mauser et al., but training features for each target word using a maximum entropy trainer is very slow (years of CPU time). More efficient training or accommodation of training of only frequent words would be useful.
- A better phrase table: The current binarised phrase table suffers from (i) far too many layers of indirection in the code making it hard to follow and inefficient (ii) a cache-locking mechanism which creates excessive contention; and (iii) lack of extensibility meaning that (e.g.) word alignments were added on by extensively duplicating code. A new phrase table could make Moses faster and more extensible.
- Multi-threaded Decoding: Moses uses a simple "thread per sentence" model for multi-threaded decoding. However this means that if you have a single sentence to decode, then multi-threading will not get you the translation any faster. Is it possible to have a finer-grained threading model that can use multiple threads on a single sentence? This would call for a new approach to decoding.
- Soft Constraints on Reordering: Moses currently allows you to specify hard constraints on reordering, but it might be useful to have "soft" versions of these constraints. This would mean that the translation would incur a trainable penalty for violating the constraints, implemented by adding a feature function.
- Sparse Reordering Features: Implementation of Cherry's Improved Reordering for Phrase-Based Translation using Sparse Features (NAACL 2013).
- Using Artificial Neural Networks as Memory to Store the Phrase Table (Hieu Hoang) ANN can be used as associative memory to store information in a lossy method. [http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=4634358&tag=1]. It would be interesting to use them to how useful they are at store the phrase table. Further research can focus on how they can be used to store morphologically similar translations.
- Python Interface: A Python interface to the decoder could enable easy experimentation and incorporation into other tools. cdec has one and Moses has a python interface to the on-disk phrase tables (implemented by Wilker Aziz) but it would be useful to be able to call the decoder from python.
- Analysis of results: (Philipp Koehn) Assessing the impact of variations in the design of a machine translation system by observing the fluctuations of the BLEU score may not be sufficiently enlightening. Having more analysis of the types of errors a system makes should be very useful.
- Integration of sigfilter: The filtering algorithm of Johnson et al is available in Moses, but it is not well integrated, has awkward external dependencies and so is seldom used. At the moment the code is in the contrib directory. A useful project would be to refactor this code to use the Moses libraries for suffix arrays, and to integrate it with the Moses experiment management system (ems). The goal would be to enable the filtering to be turned on with a simple switch in the ems config file.
- Boostification: Moses has allowed boost since Autumn 2011, but there are still many areas of the code that could be improved by usage of the boost libraries, for instance using shared pointers in collections.
- Unit-testing: The core of Moses is almost completely lacking in unit testing, although some exist for MERT and KenLM (using boost test). Increasing test coverage is a priority for 2012, and implementing unit tests is a good way of learning about the code ;-). Some refactoring will be necessary in order to make Moses "unit-testable".
- Cruise control Moses has cruise control running on a server at the University of Edinburgh, however this only tests one platform (OpenSuse). If you have a different platform, and care about keeping Moses stable on that platform, then you could set up a cruise control instance too. The code is all in the standard Moses distribution.
- Multi-pass decoding (Hieu Hoang) Moses scores all hypotheses when they are created. In some situations, it would be better to have all the hypotheses, then score them with a feature function. For example, coarse-to-fine decoding.
The are some major issues that has to be tackled with multi-pass decoding:
1. A losing hypothesis which have been recombined with the winning hypothesis may now be the new winning hypothesis. The output search graph has to be reordered to reflect this.
2. The feature functions in the 2nd pass produce state information. Recombined hypotheses may no longer be recombined and have to be split.
3. It would be useful for feature functions scores to be able to be evaluated asynchronously. That is, a function to calculate the score it called but the score is calculated later.
- Maintenance The documentation always needs maintenance as new features are introduced and old ones are updated. Such a large body of documentation inevitably contains mistakes and inconsistencies, so any help in fixing these would be most welcome. If you want to work on the documentation, just introduce yourself on the mailing list.
- Help Messages Moses has a lot of executables, and often the help messages are quite cryptic or missing. A help message in the code is more likely to be maintained than separate documentation, and easier to locate when you're trying to find the right options. Fixing the help messages would be a useful contribution to making Moses easier to use.