====== TectoMT Tutorial ====== Welcome to the TectoMT Tutorial. This tutorial should take about 3 hours. ===== What is TectoMT ===== TectoMT is a highly modular NLP (Natural Language Processing) software system implemented in Perl programming language under Linux. It is primarily aimed at Machine Translation, making use of the ideas and technology created during the Prague Dependency Treebank project. At the same time, it is also hoped to facilitate and significantly accelerate development of software solutions of many other NLP tasks, especially due to re-usability of the numerous integrated processing modules (called blocks), which are equipped with uniform object-oriented interfaces. ===== Prerequisities ===== In this tutorial, we assume * Your system is Linux * Your shell is bash * You have basic experience with bash and can read basic Perl ==== Installation and setup ==== * Checkout SVN repository. If you are running this installation in computer lab in Prague, you have to checkout the repository into directory ''~/BIG'' (because bigger disk quota applies here): cd ~/BIG svn --username public co https://svn.ms.mff.cuni.cz/svn/tectomt_devel/trunk tectomt * accept the certificate and provide a password which is same as the username ie. : //public// * In ''tectomt/install/'' run ''./install.sh'': cd tectomt/install ./install.sh * In your ''.bashrc'' file, add line (or source the specified file every time before experimenting with TectoMT): source ~/BIG/tectomt/config/init_devel_environ.sh * In your ''.bash_profile'' file, add line source .bashrc ===== TectoMT Architecture ===== ==== Blocks, scenarios and applications ==== In TectoMT, there is the following hierarchy of processing units (software components that process data): * The basic units are **blocks**. They serve for some very limited, well defined, and often linguistically interpretable tasks (e.g., tokenization, tagging, parsing). Technically, blocks are Perl classes inherited from ''TectoMT::Block'', each saved in a separate file. The blocks repository is in ''libs/blocks/''. * To solve a more complex task, selected blocks can be chained into a block sequence, called **scenario**. Scenarios are stored in ''*.scen'' files (alternatively, the block names separated by spaces can be simply listed on the command line) and at runtime the scenarios are represented by instances of ''TectoMT::Scenario'' class. * The highest unit is called **application**. Applications correspond to end-to-end tasks, be they real end-user applications (such as machine translation), or 'only' NLP-related experiments. Technically, applications are often implemented as ''Makefiles'', which only glue the components existing in TectoMT. Some demo applications can be found in ''applications''. This tutorial itself has its blocks in ''libs/blocks/Tutorial'' and the application in ''applications/tutorial''. ==== Layers of Linguistic Structures ==== {{ external:tectomt:pyramid.gif?300x190|MT pyramid in terms of PDT layers}} The notion of 'layer' has a combinatorial nature in TectoMT. It corresponds not only to the layer of language description as used e.g. in the Prague Dependency Treebank, but it is also specific for a given language (e.g., possible values of morphological tags are typically different for different languages) and even for how the data on the given layer were created (whether by analysis from the lower layer or by synthesis/transfer). Thus, the set of TectoMT layers is a Cartesian product {S,T} x {English,Czech,...} x {W,M,P,A,T}, in which: * {S,T} distinguishes whether the data was created by analysis or transfer/synthesis (mnemonics: S and T correspond to (S)ource and (T)arget in MT perspective). * {English,Czech...} represents the language in question * {W,M,P,A,T...} represents the layer of description in terms of PDT 2.0 (W - word layer, M - morphological layer, A - analytical layer, T - tectogrammatical layer) or extensions (P - phrase-structure layer). Blocks in block repository ''libs/blocks'' are located in directories indicating their purpose in machine translation. //Example//: A block adding Czech morphological tags (pos, case, gender, etc.) can be found in ''libs/blocks/SCzechW_to_SCzechM/Simple_tagger.pm''. There are also other directories for other purpose blocks, for example blocks which only print out some information go to ''libs/Print''. Our tutorial blocks are in ''libs/blocks/Tutorial/''. ===== First application ===== Once you have TectoMT installed on your machine, you can find this tutorial in ''applications/tutorial/''. After you ''cd'' into this directory, you can see our plain text sample data in ''sample.txt''. Most applications are defined in ''Makefiles'' and ''*.scen'' files, which describe sequence of blocks to be applied on our data. In our case, ''tutorial.scen'' lists four blocks to be applied on our sample text: sentence segmentation, tokenization, part-of-speech tagging and lemmatization. Since we have our input text in plain text format, the file is going to be converted into ''tmt'' format beforehand (the ''in'' target in the ''Makefile''). We can run the application: make all Our plain text data ''sample.txt'' have been transformed into ''tmt'', an internal TectoMT format, and saved into ''sample.tmt''. Then, all four blocks have been loaded and our data has been processed. We can now examine ''sample.tmt'' with a text editor (vi, emacs, etc). * One physical ''tmt'' file corresponds to one document. * A document consists of a sequence of bundles (element ''''), mirroring a sequence of natural language sentences originating from the text. So, for each sentence we have one bundle. * Each bundle contains tree shaped sentence representations on various linguistic layers. In our example ''sample.tmt'' we have morphological tree (''SEnglishM'') in each bundle (actually, it is a flat tree: one technical root and its children are the tokens). Later on, also an analytical layer (''SEnglishA'') will appear in each bundle as we proceed with our analysis. * Trees are formed by nodes and edges. Attributes can be attached only to nodes. Edge's attributes must be stored as the lower node's attributes. Tree's attributes must be stored as attributes of the root node. ===== Changing the scenario ===== We'll now add a syntax analysis (dependency parsing) to our scenario by adding five more blocks to ''tutorial.scen''. Instead of SEnglishW_to_SEnglishM::Sentence_segmentation_simple SEnglishW_to_SEnglishM::Tokenization SEnglishW_to_SEnglishM::TagMxPost SEnglishW_to_SEnglishM::Lemmatize_mtree we'll have: SEnglishW_to_SEnglishM::Sentence_segmentation_simple SEnglishW_to_SEnglishM::Tokenization SEnglishW_to_SEnglishM::TagMxPost SEnglishW_to_SEnglishM::Lemmatize_mtree SEnglishM_to_SEnglishA::Clone_MTree SEnglishM_to_SEnglishA::McD_parser SEnglishM_to_SEnglishA::Fill_is_member_from_deprel SEnglishM_to_SEnglishA::Fix_McD_topology SEnglishM_to_SEnglishA::Fill_afun_AuxCP_Coord SEnglishM_to_SEnglishA::Fill_afun After running make all we can examine our ''sample.tmt'' again. Really, an analytical layer ''SEnglishA'' describing a dependency tree with analytical functions ('''') has been added to each bundle. Blocks can also be parametrized. For syntax parser, we might want to use a smaller but faster model. To achieve this, replace the line SEnglishM_to_SEnglishA::McD_parser with SEnglishM_to_SEnglishA::McD_parser TMT_PARAM_MCD_EN_MODEL=conll_mcd_order2_0.1.model You can view the trees in ''sample.tmt'' with TrEd by typing tmttred sample.tmt Try to click on some nodes to see their parameters (tag, lemma, form, analytical function etc). //Note//: For more information about tree editor TrEd, see [[http://ufal.mff.cuni.cz/~pajas/tred/ar01-toc.html|TrEd User's Manual]]. If you are not familiar with ''Makefile'' syntax, you can run the scenario with a simple ''bash'' script (see ''applications/tutorial/run_all.sh''): ./run_all.sh ===== Adding a new block ===== The linguistic structures in TectoMT are represented using the following object-oriented interface/types: * document - ''TectoMT::Document'' * bundle - ''TectoMT::Bundle'' * node - ''TectoMT::Node'' You can get TectoMT automatically execute your block code on each document or bundle by defining the main block entry point: * ''sub process_document'' - run this procedure on each document * ''sub process_bundle'' - run this procedure on each bundle (sentence) Each block must have exactly one entry point. We'll now examine an example of a new block in file ''libs/blocks/Tutorial/Print_node_info.pm''. This block illustrates some of the most common methods for accessing objects: * ''my @bundles = $document->get_bundles()'' - an array of bundles contained in the document * ''my $root_node = $bundle->get_tree($layer_name)'' - the root node of the tree of the given type in the given bundle * ''my @children = $node->get_children()'' - array of the node's children * ''my @descendants = $node->get_descendants()'' - array of the node's children and their children and children of their children ... * ''my $parent = $node->get_parent()'' - parent node of the given node, or undef for root * ''my $root_node = $node->get_root()'' - the root node of the tree into which the node belongs Attributes of documents, bundles or nodes can be accessed by attribute getters and setters, for example: * ''$node->get_attr($attr_name)'' * ''$node->set_attr($attr_name, $attr_value)'' Some interesting attributes on morphologic layer are ''form'', ''lemma'' and ''tag''. Some interesting attributes on analytical layer are ''afun'' (analytical function) and ''ord'' (surface word order). To reach ''form'', ''lemma'' or ''tag'' from analytical layer, that is, when calling this attribute on an ''a-node'', you use ''$a_node->get_attr('m/form')'' and the same way for ''lemma'' and ''tag''. The easiest way to see the node attributes is to click on the node in TrEd: tmttred sample.tmt Our tutorial block ''Print_node_info.pm'' is ready to use. You only need to add this block to our scenario, e.g. as a new ''Makefile'' target: print_info: brunblocks -o Tutorial::Print_node_info -- sample.tmt We can observe our new block behaviour: make print_info Try to change the block so that it prints out the information only for verbs. (You need to look at an attribute ''tag'' at the ''m'' level). The tagset used is Penn Treebank Tagset. ===== Advanced block: finite clauses ===== ==== Motivation ==== It is assumed that finite clauses can be translated independently, which would reduce combinatorial complexity or make parallel translation possible. We could even use hybrid translation - each finite clause could be translated by the most self-confident translation system. In this task, we are going to split the sentence into finite clauses. ==== Task ==== A block which, given an analytical tree (''SEnglishA''), fills each ''a-node'' with boolean attribute ''is_clause_head'' which is set to ''1'' if the ''a-node'' corresponds to a finite verb, and to ''0'' otherwise. ==== Instructions ==== There is a block template with hints in ''libs/blocks/Tutorial/Mark_heads.pm''. You should edit the block so that the output of this block is the same a-tree, in addition with attribute ''is_clause_head'' attached to each ''a-node''. There is also a printing block ''libs/blocks/Print_finite_clauses.pm'' which will print out the ''a-nodes'' grouped by clauses: finite_clauses: brunblocks -S -o Tutorial::Mark_heads Tutorial::Print_finite_clauses -- sample.tmt You are going to need these methods: * ''my $root = $bundle->get_tree('tree_name')'' * ''my $attr = $node->get_attr('attr_name')'' * ''$node->set_attr('attr_name',$attr_value)'' * ''my @eff_children = $node->get_eff_children()'' //Note//: ''get_children()'' returns topological node children in a tree, while ''get_eff_children()'' returns node children in a linguistic sense. Mostly, these do not differ. If interested, see Figure 1 in [[http://ufal.mff.cuni.cz/pdt2.0/doc/tools/tred/bn-tutorial.html#i-effective|btred tutorial]]. //Hint//: Finite clauses in English usually require grammatical subject to be present. ==== Advanced version ==== The output of our block might still be incorrect in special cases - we don't solve coordination (see the second sentence in sample.txt) and subordinate conjunctions. ===== Your turn: more tasks ===== ==== SVO to SOV ==== **Motivation**: During translation from an SVO based language (e.g. English) to an SOV based language (e.g. Korean), we might need to change the word order from SVO to SOV. **Task**: Change the word order from SVO to SOV. **Instructions**: * You can use block template in ''libs/blocks/BlockTemplate.pm''. * To find an object of a verb, look for objects among effective children of a verb (''$child->get_attr('afun') eq 'Obj' ''). That implies working on analytical layer. * For debugging, a method returning surface word order of a node is useful: ''$node->get_attr('ord')''. It can be used to print out nodes sorted by attribute ''ord''. * Once you have the node ''$object'' and the node ''$verb'', use the method ''$object->shift_before_node($verb)''. This method takes the whole subtree under the node ''$object'' and recalculates the attributes ''ord'' (surface word order) so that all the nodes in the subtree under ''$object'' have a smaller ''ord'' than ''$verb''. That is, the method rearranges the surface word order from VO to OV. **Advanced version**: This solution shifts object (or more objects) of a verb just in front of that verb node. So f.e.: //Mr. Brown has urged MPs.// changes to: //Mr. Brown has MPs urged.// You can try to change this solution, so the final sentence would be: //Mr. Brown MPs has urged.// You may need a method ''$node->shift_after_subtree($root_of_that_subtree)''. Subjects should have attribute '''afun' eq 'Sb'''. ==== Prepositions ==== {{ external:tectomt:preps.png?200x80|Prepositions example}} **Motivation**: In dependency approach the question "where to hang prepositions" arises. In the praguian style (PDT), prepositions are heads of the subtree and the noun/pronoun is dependent on the preposition. However, another ordering might be preferable: The noun/pronoun might be the head of subtree, while the preposition would take the role of a modifier. **Task**: The task is to rehang all prepositions as indicated at the picture. You may assume that prepositions have at most 1 child. ** Instructions**: You are going to need these new methods: * ''my @children = $node->get_children()'' * ''my $parent = $node->get_parent()'' * ''$node->set_parent($parent)'' //Hint//: * On analytical layer, you can use this test to recognize prepositions: ''$node->get_attr('afun') eq 'AuxP' '' * To see the results, you can again use TrEd (''tmttred sample.tmt'') **Advanced version**: What happens in case of multiword prepositions? For example, ''because of'', ''instead of''. Can you handle it? ===== Further information ===== * [[http://ufal.mff.cuni.cz/tectomt|TectoMT Homepage]] * Questions? Ask ''kravalova'' at ''ufal.mff.cuni.cz'' * Solutions to this tutorial tasks are in ''libs/blocks/Tutorial/*solution*.pm''. * [[http://ufal.mff.cuni.cz/~pajas/tred/|TrEd]], [[http://ufal.mff.cuni.cz/~pajas/tred/ar01-toc.html|TrEd User's Manual]] - tree editor If you are missing some files from //share//, you can download it from [[http://ufallab.ms.mff.cuni.cz/tectomt/share/]].