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| author | aarne <aarne@chalmers.se> | 2010-12-22 14:08:42 +0000 |
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| committer | aarne <aarne@chalmers.se> | 2010-12-22 14:08:42 +0000 |
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diff --git a/deprecated/Resource-HOWTO.html b/deprecated/Resource-HOWTO.html new file mode 100644 index 000000000..ce2c15137 --- /dev/null +++ b/deprecated/Resource-HOWTO.html @@ -0,0 +1,967 @@ +<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> +<HTML> +<HEAD> +<META NAME="generator" CONTENT="http://txt2tags.sf.net"> +<TITLE>Resource grammar writing HOWTO</TITLE> +</HEAD><BODY BGCOLOR="white" TEXT="black"> +<P ALIGN="center"><CENTER><H1>Resource grammar writing HOWTO</H1> +<FONT SIZE="4"> +<I>Author: Aarne Ranta <aarne (at) cs.chalmers.se></I><BR> +Last update: Mon Sep 22 14:28:01 2008 +</FONT></CENTER> + +<P></P> +<HR NOSHADE SIZE=1> +<P></P> + <UL> + <LI><A HREF="#toc1">The resource grammar structure</A> + <UL> + <LI><A HREF="#toc2">Library API modules</A> + <LI><A HREF="#toc3">Phrase category modules</A> + <LI><A HREF="#toc4">Infrastructure modules</A> + <LI><A HREF="#toc5">Lexical modules</A> + </UL> + <LI><A HREF="#toc6">Language-dependent syntax modules</A> + <UL> + <LI><A HREF="#toc7">The present-tense fragment</A> + </UL> + <LI><A HREF="#toc8">Phases of the work</A> + <UL> + <LI><A HREF="#toc9">Putting up a directory</A> + <LI><A HREF="#toc10">Direction of work</A> + <LI><A HREF="#toc11">The develop-test cycle</A> + <LI><A HREF="#toc12">Auxiliary modules</A> + <LI><A HREF="#toc13">Morphology and lexicon</A> + <LI><A HREF="#toc14">Lock fields</A> + <LI><A HREF="#toc15">Lexicon construction</A> + </UL> + <LI><A HREF="#toc16">Lexicon extension</A> + <UL> + <LI><A HREF="#toc17">The irregularity lexicon</A> + <LI><A HREF="#toc18">Lexicon extraction from a word list</A> + <LI><A HREF="#toc19">Lexicon extraction from raw text data</A> + <LI><A HREF="#toc20">Bootstrapping with smart paradigms</A> + </UL> + <LI><A HREF="#toc21">Extending the resource grammar API</A> + <LI><A HREF="#toc22">Using parametrized modules</A> + <UL> + <LI><A HREF="#toc23">Writing an instance of parametrized resource grammar implementation</A> + <LI><A HREF="#toc24">Parametrizing a resource grammar implementation</A> + </UL> + <LI><A HREF="#toc25">Character encoding and transliterations</A> + <LI><A HREF="#toc26">Coding conventions in GF</A> + <LI><A HREF="#toc27">Transliterations</A> + </UL> + +<P></P> +<HR NOSHADE SIZE=1> +<P></P> +<P> +<B>History</B> +</P> +<P> +September 2008: updated for Version 1.5. +</P> +<P> +October 2007: updated for Version 1.2. +</P> +<P> +January 2006: first version. +</P> +<P> +The purpose of this document is to tell how to implement the GF +resource grammar API for a new language. We will <I>not</I> cover how +to use the resource grammar, nor how to change the API. But we +will give some hints how to extend the API. +</P> +<P> +A manual for using the resource grammar is found in +</P> +<P> +<A HREF="../lib/resource/doc/synopsis.html"><CODE>www.cs.chalmers.se/Cs/Research/Language-technology/GF/lib/resource/doc/synopsis.html</CODE></A>. +</P> +<P> +A tutorial on GF, also introducing the idea of resource grammars, is found in +</P> +<P> +<A HREF="./gf-tutorial.html"><CODE>www.cs.chalmers.se/Cs/Research/Language-technology/GF/doc/gf-tutorial.html</CODE></A>. +</P> +<P> +This document concerns the API v. 1.5, while the current stable release is 1.4. +You can find the code for the stable release in +</P> +<P> +<A HREF="../lib/resource"><CODE>www.cs.chalmers.se/Cs/Research/Language-technology/GF/lib/resource/</CODE></A> +</P> +<P> +and the next release in +</P> +<P> +<A HREF="../next-lib/src"><CODE>www.cs.chalmers.se/Cs/Research/Language-technology/GF/next-lib/src/</CODE></A> +</P> +<P> +It is recommended to build new grammars to match the next release. +</P> +<A NAME="toc1"></A> +<H2>The resource grammar structure</H2> +<P> +The library is divided into a bunch of modules, whose dependencies +are given in the following figure. +</P> +<P> +<IMG ALIGN="left" SRC="Syntax.png" BORDER="0" ALT=""> +</P> +<P> +Modules of different kinds are distinguished as follows: +</P> +<UL> +<LI>solid contours: module seen by end users +<LI>dashed contours: internal module +<LI>ellipse: abstract/concrete pair of modules +<LI>rectangle: resource or instance +<LI>diamond: interface +</UL> + +<P> +Put in another way: +</P> +<UL> +<LI>solid rectangles and diamonds: user-accessible library API +<LI>solid ellipses: user-accessible top-level grammar for parsing and linearization +<LI>dashed contours: not visible to users +</UL> + +<P> +The dashed ellipses form the main parts of the implementation, on which the resource +grammar programmer has to work with. She also has to work on the <CODE>Paradigms</CODE> +module. The rest of the modules can be produced mechanically from corresponding +modules for other languages, by just changing the language codes appearing in +their module headers. +</P> +<P> +The module structure is rather flat: most modules are direct +parents of <CODE>Grammar</CODE>. The idea +is that the implementors can concentrate on one linguistic aspect at a time, or +also distribute the work among several authors. The module <CODE>Cat</CODE> +defines the "glue" that ties the aspects together - a type system +to which all the other modules conform, so that e.g. <CODE>NP</CODE> means +the same thing in those modules that use <CODE>NP</CODE>s and those that +constructs them. +</P> +<A NAME="toc2"></A> +<H3>Library API modules</H3> +<P> +For the user of the library, these modules are the most important ones. +In a typical application, it is enough to open <CODE>Paradigms</CODE> and <CODE>Syntax</CODE>. +The module <CODE>Try</CODE> combines these two, making it possible to experiment +with combinations of syntactic and lexical constructors by using the +<CODE>cc</CODE> command in the GF shell. Here are short explanations of each API module: +</P> +<UL> +<LI><CODE>Try</CODE>: the whole resource library for a language (<CODE>Paradigms</CODE>, <CODE>Syntax</CODE>, + <CODE>Irreg</CODE>, and <CODE>Extra</CODE>); + produced mechanically as a collection of modules +<LI><CODE>Syntax</CODE>: language-independent categories, syntax functions, and structural words; + produced mechanically as a collection of modules +<LI><CODE>Constructors</CODE>: language-independent syntax functions and structural words; + produced mechanically via functor instantiation +<LI><CODE>Paradigms</CODE>: language-dependent morphological paradigms +</UL> + +<A NAME="toc3"></A> +<H3>Phrase category modules</H3> +<P> +The immediate parents of <CODE>Grammar</CODE> will be called <B>phrase category modules</B>, +since each of them concentrates on a particular phrase category (nouns, verbs, +adjectives, sentences,...). A phrase category module tells +<I>how to construct phrases in that category</I>. You will find out that +all functions in any of these modules have the same value type (or maybe +one of a small number of different types). Thus we have +</P> +<UL> +<LI><CODE>Noun</CODE>: construction of nouns and noun phrases +<LI><CODE>Adjective</CODE>: construction of adjectival phrases +<LI><CODE>Verb</CODE>: construction of verb phrases +<LI><CODE>Adverb</CODE>: construction of adverbial phrases +<LI><CODE>Numeral</CODE>: construction of cardinal and ordinal numerals +<LI><CODE>Sentence</CODE>: construction of sentences and imperatives +<LI><CODE>Question</CODE>: construction of questions +<LI><CODE>Relative</CODE>: construction of relative clauses +<LI><CODE>Conjunction</CODE>: coordination of phrases +<LI><CODE>Phrase</CODE>: construction of the major units of text and speech +<LI><CODE>Text</CODE>: construction of texts as sequences of phrases +<LI><CODE>Idiom</CODE>: idiomatic expressions such as existentials +</UL> + +<A NAME="toc4"></A> +<H3>Infrastructure modules</H3> +<P> +Expressions of each phrase category are constructed in the corresponding +phrase category module. But their <I>use</I> takes mostly place in other modules. +For instance, noun phrases, which are constructed in <CODE>Noun</CODE>, are +used as arguments of functions of almost all other phrase category modules. +How can we build all these modules independently of each other? +</P> +<P> +As usual in typeful programming, the <I>only</I> thing you need to know +about an object you use is its type. When writing a linearization rule +for a GF abstract syntax function, the only thing you need to know is +the linearization types of its value and argument categories. To achieve +the division of the resource grammar to several parallel phrase category modules, +what we need is an underlying definition of the linearization types. This +definition is given as the implementation of +</P> +<UL> +<LI><CODE>Cat</CODE>: syntactic categories of the resource grammar +</UL> + +<P> +Any resource grammar implementation has first to agree on how to implement +<CODE>Cat</CODE>. Luckily enough, even this can be done incrementally: you +can skip the <CODE>lincat</CODE> definition of a category and use the default +<CODE>{s : Str}</CODE> until you need to change it to something else. In +English, for instance, many categories do have this linearization type. +</P> +<A NAME="toc5"></A> +<H3>Lexical modules</H3> +<P> +What is lexical and what is syntactic is not as clearcut in GF as in +some other grammar formalisms. Logically, lexical means atom, i.e. a +<CODE>fun</CODE> with no arguments. Linguistically, one may add to this +that the <CODE>lin</CODE> consists of only one token (or of a table whose values +are single tokens). Even in the restricted lexicon included in the resource +API, the latter rule is sometimes violated in some languages. For instance, +<CODE>Structural.both7and_DConj</CODE> is an atom, but its linearization is +two words e.g. <I>both - and</I>. +</P> +<P> +Another characterization of lexical is that lexical units can be added +almost <I>ad libitum</I>, and they cannot be defined in terms of already +given rules. The lexical modules of the resource API are thus more like +samples than complete lists. There are two such modules: +</P> +<UL> +<LI><CODE>Structural</CODE>: structural words (determiners, conjunctions,...) +<LI><CODE>Lexicon</CODE>: basic everyday content words (nouns, verbs,...) +</UL> + +<P> +The module <CODE>Structural</CODE> aims for completeness, and is likely to +be extended in future releases of the resource. The module <CODE>Lexicon</CODE> +gives a "random" list of words, which enables testing the syntax. +It also provides a check list for morphology, since those words are likely to include +most morphological patterns of the language. +</P> +<P> +In the case of <CODE>Lexicon</CODE> it may come out clearer than anywhere else +in the API that it is impossible to give exact translation equivalents in +different languages on the level of a resource grammar. This is no problem, +since application grammars can use the resource in different ways for +different languages. +</P> +<A NAME="toc6"></A> +<H2>Language-dependent syntax modules</H2> +<P> +In addition to the common API, there is room for language-dependent extensions +of the resource. The top level of each languages looks as follows (with German +as example): +</P> +<PRE> + abstract AllGerAbs = Lang, ExtraGerAbs, IrregGerAbs +</PRE> +<P> +where <CODE>ExtraGerAbs</CODE> is a collection of syntactic structures specific to German, +and <CODE>IrregGerAbs</CODE> is a dictionary of irregular words of German +(at the moment, just verbs). Each of these language-specific grammars has +the potential to grow into a full-scale grammar of the language. These grammar +can also be used as libraries, but the possibility of using functors is lost. +</P> +<P> +To give a better overview of language-specific structures, +modules like <CODE>ExtraGerAbs</CODE> +are built from a language-independent module <CODE>ExtraAbs</CODE> +by restricted inheritance: +</P> +<PRE> + abstract ExtraGerAbs = Extra [f,g,...] +</PRE> +<P> +Thus any category and function in <CODE>Extra</CODE> may be shared by a subset of all +languages. One can see this set-up as a matrix, which tells +what <CODE>Extra</CODE> structures +are implemented in what languages. For the common API in <CODE>Grammar</CODE>, the matrix +is filled with 1's (everything is implemented in every language). +</P> +<P> +In a minimal resource grammar implementation, the language-dependent +extensions are just empty modules, but it is good to provide them for +the sake of uniformity. +</P> +<A NAME="toc7"></A> +<H3>The present-tense fragment</H3> +<P> +Some lines in the resource library are suffixed with the comment +</P> +<PRE> + --# notpresent +</PRE> +<P> +which is used by a preprocessor to exclude those lines from +a reduced version of the full resource. This present-tense-only +version is useful for applications in most technical text, since +they reduce the grammar size and compilation time. It can also +be useful to exclude those lines in a first version of resource +implementation. To compile a grammar with present-tense-only, use +</P> +<PRE> + make Present +</PRE> +<P> +with <CODE>resource/Makefile</CODE>. +</P> +<A NAME="toc8"></A> +<H2>Phases of the work</H2> +<A NAME="toc9"></A> +<H3>Putting up a directory</H3> +<P> +Unless you are writing an instance of a parametrized implementation +(Romance or Scandinavian), which will be covered later, the +simplest way is to follow roughly the following procedure. Assume you +are building a grammar for the German language. Here are the first steps, +which we actually followed ourselves when building the German implementation +of resource v. 1.0 at Ubuntu linux. We have slightly modified them to +match resource v. 1.5 and GF v. 3.0. +</P> +<OL> +<LI>Create a sister directory for <CODE>GF/lib/resource/english</CODE>, named + <CODE>german</CODE>. +<PRE> + cd GF/lib/resource/ + mkdir german + cd german +</PRE> +<P></P> +<LI>Check out the [ISO 639 3-letter language code + <A HREF="http://www.w3.org/WAI/ER/IG/ert/iso639.htm">http://www.w3.org/WAI/ER/IG/ert/iso639.htm</A>] + for German: both <CODE>Ger</CODE> and <CODE>Deu</CODE> are given, and we pick <CODE>Ger</CODE>. + (We use the 3-letter codes rather than the more common 2-letter codes, + since they will suffice for many more languages!) +<P></P> +<LI>Copy the <CODE>*Eng.gf</CODE> files from <CODE>english</CODE> <CODE>german</CODE>, + and rename them: +<PRE> + cp ../english/*Eng.gf . + rename 's/Eng/Ger/' *Eng.gf +</PRE> + If you don't have the <CODE>rename</CODE> command, you can use a bash script with <CODE>mv</CODE>. +</OL> + +<OL> +<LI>Change the <CODE>Eng</CODE> module references to <CODE>Ger</CODE> references + in all files: +<PRE> + sed -i 's/English/German/g' *Ger.gf + sed -i 's/Eng/Ger/g' *Ger.gf +</PRE> + The first line prevents changing the word <CODE>English</CODE>, which appears + here and there in comments, to <CODE>Gerlish</CODE>. The <CODE>sed</CODE> command syntax + may vary depending on your operating system. +<P></P> +<LI>This may of course change unwanted occurrences of the + string <CODE>Eng</CODE> - verify this by +<PRE> + grep Ger *.gf +</PRE> + But you will have to make lots of manual changes in all files anyway! +<P></P> +<LI>Comment out the contents of these files: +<PRE> + sed -i 's/^/--/' *Ger.gf +</PRE> + This will give you a set of templates out of which the grammar + will grow as you uncomment and modify the files rule by rule. +<P></P> +<LI>In all <CODE>.gf</CODE> files, uncomment the module headers and brackets, + leaving the module bodies commented. Unfortunately, there is no + simple way to do this automatically (or to avoid commenting these + lines in the previous step) - but uncommenting the first + and the last lines will actually do the job for many of the files. +<P></P> +<LI>Uncomment the contents of the main grammar file: +<PRE> + sed -i 's/^--//' LangGer.gf +</PRE> +<P></P> +<LI>Now you can open the grammar <CODE>LangGer</CODE> in GF: +<PRE> + gf LangGer.gf +</PRE> + You will get lots of warnings on missing rules, but the grammar will compile. +<P></P> +<LI>At all the following steps you will now have a valid, but incomplete + GF grammar. The GF command +<PRE> + pg -missing +</PRE> + tells you what exactly is missing. +</OL> + +<P> +Here is the module structure of <CODE>LangGer</CODE>. It has been simplified by leaving out +the majority of the phrase category modules. Each of them has the same dependencies +as <CODE>VerbGer</CODE>, whose complete dependencies are shown as an example. +</P> +<P> +<IMG ALIGN="middle" SRC="German.png" BORDER="0" ALT=""> +</P> +<A NAME="toc10"></A> +<H3>Direction of work</H3> +<P> +The real work starts now. There are many ways to proceed, the most obvious ones being +</P> +<UL> +<LI>Top-down: start from the module <CODE>Phrase</CODE> and go down to <CODE>Sentence</CODE>, then + <CODE>Verb</CODE>, <CODE>Noun</CODE>, and in the end <CODE>Lexicon</CODE>. In this way, you are all the time + building complete phrases, and add them with more content as you proceed. + <B>This approach is not recommended</B>. It is impossible to test the rules if + you have no words to apply the constructions to. +<P></P> +<LI>Bottom-up: set as your first goal to implement <CODE>Lexicon</CODE>. To this end, you + need to write <CODE>ParadigmsGer</CODE>, which in turn needs parts of + <CODE>MorphoGer</CODE> and <CODE>ResGer</CODE>. + <B>This approach is not recommended</B>. You can get stuck to details of + morphology such as irregular words, and you don't have enough grasp about + the type system to decide what forms to cover in morphology. +</UL> + +<P> +The practical working direction is thus a saw-like motion between the morphological +and top-level modules. Here is a possible course of the work that gives enough +test data and enough general view at any point: +</P> +<OL> +<LI>Define <CODE>Cat.N</CODE> and the required parameter types in <CODE>ResGer</CODE>. As we define +<PRE> + lincat N = {s : Number => Case => Str ; g : Gender} ; +</PRE> +we need the parameter types <CODE>Number</CODE>, <CODE>Case</CODE>, and <CODE>Gender</CODE>. The definition +of <CODE>Number</CODE> in <A HREF="../lib/resource/common/ParamX.gf"><CODE>common/ParamX</CODE></A> +works for German, so we +use it and just define <CODE>Case</CODE> and <CODE>Gender</CODE> in <CODE>ResGer</CODE>. +<P></P> +<LI>Define some cases of <CODE>mkN</CODE> in <CODE>ParadigmsGer</CODE>. In this way you can +already implement a huge amount of nouns correctly in <CODE>LexiconGer</CODE>. Actually +just adding the worst-case instance of <CODE>mkN</CODE> (the one taking the most +arguments) should suffice for every noun - but, +since it is tedious to use, you +might proceed to the next step before returning to morphology and defining the +real work horse, <CODE>mkN</CODE> taking two forms and a gender. +<P></P> +<LI>While doing this, you may want to test the resource independently. Do this by + starting the GF shell in the <CODE>resource</CODE> directory, by the commands +<PRE> + > i -retain german/ParadigmsGer + > cc -table mkN "Kirche" +</PRE> +<P></P> +<LI>Proceed to determiners and pronouns in +<CODE>NounGer</CODE> (<CODE>DetCN UsePron DetQuant NumSg DefArt IndefArt UseN</CODE>) and +<CODE>StructuralGer</CODE> (<CODE>i_Pron this_Quant</CODE>). You also need some categories and +parameter types. At this point, it is maybe not possible to find out the final +linearization types of <CODE>CN</CODE>, <CODE>NP</CODE>, <CODE>Det</CODE>, and <CODE>Quant</CODE>, but at least you should +be able to correctly inflect noun phrases such as <I>every airplane</I>: +<PRE> + > i german/LangGer.gf + > l -table DetCN every_Det (UseN airplane_N) + + Nom: jeder Flugzeug + Acc: jeden Flugzeug + Dat: jedem Flugzeug + Gen: jedes Flugzeugs +</PRE> +<P></P> +<LI>Proceed to verbs: define <CODE>CatGer.V</CODE>, <CODE>ResGer.VForm</CODE>, and +<CODE>ParadigmsGer.mkV</CODE>. You may choose to exclude <CODE>notpresent</CODE> +cases at this point. But anyway, you will be able to inflect a good +number of verbs in <CODE>Lexicon</CODE>, such as +<CODE>live_V</CODE> (<CODE>mkV "leben"</CODE>). +<P></P> +<LI>Now you can soon form your first sentences: define <CODE>VP</CODE> and +<CODE>Cl</CODE> in <CODE>CatGer</CODE>, <CODE>VerbGer.UseV</CODE>, and <CODE>SentenceGer.PredVP</CODE>. +Even if you have excluded the tenses, you will be able to produce +<PRE> + > i -preproc=./mkPresent german/LangGer.gf + > l -table PredVP (UsePron i_Pron) (UseV live_V) + + Pres Simul Pos Main: ich lebe + Pres Simul Pos Inv: lebe ich + Pres Simul Pos Sub: ich lebe + Pres Simul Neg Main: ich lebe nicht + Pres Simul Neg Inv: lebe ich nicht + Pres Simul Neg Sub: ich nicht lebe +</PRE> +You should also be able to parse: +<PRE> + > p -cat=Cl "ich lebe" + PredVP (UsePron i_Pron) (UseV live_V) +</PRE> +<P></P> +<LI>Transitive verbs +(<CODE>CatGer.V2 CatGer.VPSlash ParadigmsGer.mkV2 VerbGer.ComplSlash VerbGer.SlashV2a</CODE>) +are a natural next step, so that you can +produce <CODE>ich liebe dich</CODE> ("I love you"). +<P></P> +<LI>Adjectives (<CODE>CatGer.A ParadigmsGer.mkA NounGer.AdjCN AdjectiveGer.PositA</CODE>) +will force you to think about strong and weak declensions, so that you can +correctly inflect <I>mein neuer Wagen, dieser neue Wagen</I> +("my new car, this new car"). +<P></P> +<LI>Once you have implemented the set +(``Noun.DetCN Noun.AdjCN Verb.UseV Verb.ComplSlash Verb.SlashV2a Sentence.PredVP), +you have overcome most of difficulties. You know roughly what parameters +and dependences there are in your language, and you can now proceed very +much in the order you please. +</OL> + +<A NAME="toc11"></A> +<H3>The develop-test cycle</H3> +<P> +The following develop-test cycle will +be applied most of the time, both in the first steps described above +and in later steps where you are more on your own. +</P> +<OL> +<LI>Select a phrase category module, e.g. <CODE>NounGer</CODE>, and uncomment some + linearization rules (for instance, <CODE>DetCN</CODE>, as above). +<P></P> +<LI>Write down some German examples of this rule, for instance translations + of "the dog", "the house", "the big house", etc. Write these in all their + different forms (two numbers and four cases). +<P></P> +<LI>Think about the categories involved (<CODE>CN, NP, N, Det</CODE>) and the + variations they have. Encode this in the lincats of <CODE>CatGer</CODE>. + You may have to define some new parameter types in <CODE>ResGer</CODE>. +<P></P> +<LI>To be able to test the construction, + define some words you need to instantiate it + in <CODE>LexiconGer</CODE>. You will also need some regular inflection patterns + in<CODE>ParadigmsGer</CODE>. +<P></P> +<LI>Test by parsing, linearization, + and random generation. In particular, linearization to a table should + be used so that you see all forms produced; the <CODE>treebank</CODE> option + preserves the tree +<PRE> + > gr -cat=NP -number=20 | l -table -treebank +</PRE> +<P></P> +<LI>Save some tree-linearization pairs for later regression testing. You can save + a gold standard treebank and use the Unix <CODE>diff</CODE> command to compare later + linearizations produced from the same list of trees. If you save the trees + in a file <CODE>trees</CODE>, you can do as follows: +<PRE> + > rf -file=trees -tree -lines | l -table -treebank | wf -file=treebank +</PRE> +<P></P> +<LI>A file with trees testing all resource functions is included in the resource, + entitled <CODE>resource/exx-resource.gft</CODE>. A treebank can be created from this by + the Unix command +<PRE> + % runghc Make.hs test langs=Ger +</PRE> +</OL> + +<P> +You are likely to run this cycle a few times for each linearization rule +you implement, and some hundreds of times altogether. There are roughly +70 <CODE>cat</CODE>s and +600 <CODE>funs</CODE> in <CODE>Lang</CODE> at the moment; 170 of the <CODE>funs</CODE> are outside the two +lexicon modules). +</P> +<A NAME="toc12"></A> +<H3>Auxiliary modules</H3> +<P> +These auxuliary <CODE>resource</CODE> modules will be written by you. +</P> +<UL> +<LI><CODE>ResGer</CODE>: parameter types and auxiliary operations +(a resource for the resource grammar!) +<LI><CODE>ParadigmsGer</CODE>: complete inflection engine and most important regular paradigms +<LI><CODE>MorphoGer</CODE>: auxiliaries for <CODE>ParadigmsGer</CODE> and <CODE>StructuralGer</CODE>. This need +not be separate from <CODE>ResGer</CODE>. +</UL> + +<P> +These modules are language-independent and provided by the existing resource +package. +</P> +<UL> +<LI><CODE>ParamX</CODE>: parameter types used in many languages +<LI><CODE>CommonX</CODE>: implementation of language-uniform categories + such as $Text$ and $Phr$, as well as of + the logical tense, anteriority, and polarity parameters +<LI><CODE>Coordination</CODE>: operations to deal with lists and coordination +<LI><CODE>Prelude</CODE>: general-purpose operations on strings, records, + truth values, etc. +<LI><CODE>Predef</CODE>: general-purpose operations with hard-coded definitions +</UL> + +<P> +An important decision is what rules to implement in terms of operations in +<CODE>ResGer</CODE>. The <B>golden rule of functional programming</B> says: +</P> +<UL> +<LI><I>Whenever you find yourself programming by copy and paste, write a function instead!</I>. +</UL> + +<P> +This rule suggests that an operation should be created if it is to be +used at least twice. At the same time, a sound principle of <B>vicinity</B> says: +</P> +<UL> +<LI><I>It should not require too much browsing to understand what a piece of code does.</I> +</UL> + +<P> +From these two principles, we have derived the following practice: +</P> +<UL> +<LI>If an operation is needed <I>in two different modules</I>, + it should be created in as an <CODE>oper</CODE> in <CODE>ResGer</CODE>. An example is <CODE>mkClause</CODE>, + used in <CODE>Sentence</CODE>, <CODE>Question</CODE>, and <CODE>Relative</CODE>- +<LI>If an operation is needed <I>twice in the same module</I>, but never + outside, it should be created in the same module. Many examples are + found in <CODE>Numerals</CODE>. +<LI>If an operation is needed <I>twice in the same judgement</I>, but never + outside, it should be created by a <CODE>let</CODE> definition. +<LI>If an operation is only needed once, it should not be created as an <CODE>oper</CODE>, + but rather inlined. However, a <CODE>let</CODE> definition may well be in place just + to make the readable. + Most functions in phrase category modules + are implemented in this way. +</UL> + +<P> +This discipline is very different from the one followed in early +versions of the library (up to 0.9). We then valued the principle of +abstraction more than vicinity, creating layers of abstraction for +almost everything. This led in practice to the duplication of almost +all code on the <CODE>lin</CODE> and <CODE>oper</CODE> levels, and made the code +hard to understand and maintain. +</P> +<A NAME="toc13"></A> +<H3>Morphology and lexicon</H3> +<P> +The paradigms needed to implement +<CODE>LexiconGer</CODE> are defined in +<CODE>ParadigmsGer</CODE>. +This module provides high-level ways to define the linearization of +lexical items, of categories <CODE>N, A, V</CODE> and their complement-taking +variants. +</P> +<P> +For ease of use, the <CODE>Paradigms</CODE> modules follow a certain +naming convention. Thus they for each lexical category, such as <CODE>N</CODE>, +the overloaded functions, such as <CODE>mkN</CODE>, with the following cases: +</P> +<UL> +<LI>the worst-case construction of <CODE>N</CODE>. Its type signature + has the form +<PRE> + mkN : Str -> ... -> Str -> P -> ... -> Q -> N +</PRE> + with as many string and parameter arguments as can ever be needed to + construct an <CODE>N</CODE>. +<LI>the most regular cases, with just one string argument: +<PRE> + mkN : Str -> N +</PRE> +<LI>A language-dependent (small) set of functions to handle mild irregularities + and common exceptions. +</UL> + +<P> +For the complement-taking variants, such as <CODE>V2</CODE>, we provide +</P> +<UL> +<LI>a case that takes a <CODE>V</CODE> and all necessary arguments, such + as case and preposition: +<PRE> + mkV2 : V -> Case -> Str -> V2 ; +</PRE> +<LI>a case that takes a <CODE>Str</CODE> and produces a transitive verb with the direct + object case: +<PRE> + mkV2 : Str -> V2 ; +</PRE> +<LI>A language-dependent (small) set of functions to handle common special cases, + such as transitive verbs that are not regular: +<PRE> + mkV2 : V -> V2 ; +</PRE> +</UL> + +<P> +The golden rule for the design of paradigms is that +</P> +<UL> +<LI><I>The user of the library will only need function applications with constants and strings, never any records or tables.</I> +</UL> + +<P> +The discipline of data abstraction moreover requires that the user of the resource +is not given access to parameter constructors, but only to constants that denote +them. This gives the resource grammarian the freedom to change the underlying +data representation if needed. It means that the <CODE>ParadigmsGer</CODE> module has +to define constants for those parameter types and constructors that +the application grammarian may need to use, e.g. +</P> +<PRE> + oper + Case : Type ; + nominative, accusative, genitive, dative : Case ; +</PRE> +<P> +These constants are defined in terms of parameter types and constructors +in <CODE>ResGer</CODE> and <CODE>MorphoGer</CODE>, which modules are not +visible to the application grammarian. +</P> +<A NAME="toc14"></A> +<H3>Lock fields</H3> +<P> +An important difference between <CODE>MorphoGer</CODE> and +<CODE>ParadigmsGer</CODE> is that the former uses "raw" record types +for word classes, whereas the latter used category symbols defined in +<CODE>CatGer</CODE>. When these category symbols are used to denote +record types in a resource modules, such as <CODE>ParadigmsGer</CODE>, +a <B>lock field</B> is added to the record, so that categories +with the same implementation are not confused with each other. +(This is inspired by the <CODE>newtype</CODE> discipline in Haskell.) +For instance, the lincats of adverbs and conjunctions are the same +in <CODE>CommonX</CODE> (and therefore in <CODE>CatGer</CODE>, which inherits it): +</P> +<PRE> + lincat Adv = {s : Str} ; + lincat Conj = {s : Str} ; +</PRE> +<P> +But when these category symbols are used to denote their linearization +types in resource module, these definitions are translated to +</P> +<PRE> + oper Adv : Type = {s : Str ; lock_Adv : {}} ; + oper Conj : Type = {s : Str} ; lock_Conj : {}} ; +</PRE> +<P> +In this way, the user of a resource grammar cannot confuse adverbs with +conjunctions. In other words, the lock fields force the type checker +to function as grammaticality checker. +</P> +<P> +When the resource grammar is <CODE>open</CODE>ed in an application grammar, the +lock fields are never seen (except possibly in type error messages), +and the application grammarian should never write them herself. If she +has to do this, it is a sign that the resource grammar is incomplete, and +the proper way to proceed is to fix the resource grammar. +</P> +<P> +The resource grammarian has to provide the dummy lock field values +in her hidden definitions of constants in <CODE>Paradigms</CODE>. For instance, +</P> +<PRE> + mkAdv : Str -> Adv ; + -- mkAdv s = {s = s ; lock_Adv = <>} ; +</PRE> +<P></P> +<A NAME="toc15"></A> +<H3>Lexicon construction</H3> +<P> +The lexicon belonging to <CODE>LangGer</CODE> consists of two modules: +</P> +<UL> +<LI><CODE>StructuralGer</CODE>, structural words, built by using both + <CODE>ParadigmsGer</CODE> and <CODE>MorphoGer</CODE>. +<LI><CODE>LexiconGer</CODE>, content words, built by using <CODE>ParadigmsGer</CODE> only. +</UL> + +<P> +The reason why <CODE>MorphoGer</CODE> has to be used in <CODE>StructuralGer</CODE> +is that <CODE>ParadigmsGer</CODE> does not contain constructors for closed +word classes such as pronouns and determiners. The reason why we +recommend <CODE>ParadigmsGer</CODE> for building <CODE>LexiconGer</CODE> is that +the coverage of the paradigms gets thereby tested and that the +use of the paradigms in <CODE>LexiconGer</CODE> gives a good set of examples for +those who want to build new lexica. +</P> +<A NAME="toc16"></A> +<H2>Lexicon extension</H2> +<A NAME="toc17"></A> +<H3>The irregularity lexicon</H3> +<P> +It is useful in most languages to provide a separate module of irregular +verbs and other words which are difficult for a lexicographer +to handle. There are usually a limited number of such words - a +few hundred perhaps. Building such a lexicon separately also +makes it less important to cover <I>everything</I> by the +worst-case variants of the paradigms <CODE>mkV</CODE> etc. +</P> +<A NAME="toc18"></A> +<H3>Lexicon extraction from a word list</H3> +<P> +You can often find resources such as lists of +irregular verbs on the internet. For instance, the +Irregular German Verb page +previously found in +<CODE>http://www.iee.et.tu-dresden.de/~wernerr/grammar/verben_dt.html</CODE> +page gives a list of verbs in the +traditional tabular format, which begins as follows: +</P> +<PRE> + backen (du bäckst, er bäckt) backte [buk] gebacken + befehlen (du befiehlst, er befiehlt; befiehl!) befahl (beföhle; befähle) befohlen + beginnen begann (begönne; begänne) begonnen + beißen biß gebissen +</PRE> +<P> +All you have to do is to write a suitable verb paradigm +</P> +<PRE> + irregV : (x1,_,_,_,_,x6 : Str) -> V ; +</PRE> +<P> +and a Perl or Python or Haskell script that transforms +the table to +</P> +<PRE> + backen_V = irregV "backen" "bäckt" "back" "backte" "backte" "gebacken" ; + befehlen_V = irregV "befehlen" "befiehlt" "befiehl" "befahl" "beföhle" "befohlen" ; +</PRE> +<P></P> +<P> +When using ready-made word lists, you should think about +coyright issues. All resource grammar material should +be provided under GNU Lesser General Public License (LGPL). +</P> +<A NAME="toc19"></A> +<H3>Lexicon extraction from raw text data</H3> +<P> +This is a cheap technique to build a lexicon of thousands +of words, if text data is available in digital format. +See the <A HREF="http://www.cs.chalmers.se/~markus/extract/">Extract Homepage</A> +homepage for details. +</P> +<A NAME="toc20"></A> +<H3>Bootstrapping with smart paradigms</H3> +<P> +This is another cheap technique, where you need as input a list of words with +part-of-speech marking. You initialize the lexicon by using the one-argument +<CODE>mkN</CODE> etc paradigms, and add forms to those words that do not come out right. +This procedure is described in the paper +</P> +<P> +A. Ranta. +How predictable is Finnish morphology? An experiment on lexicon construction. +In J. Nivre, M. Dahllöf and B. Megyesi (eds), +<I>Resourceful Language Technology: Festschrift in Honor of Anna Sågvall Hein</I>, +University of Uppsala, +2008. +Available from the <A HREF="http://publications.uu.se/abstract.xsql?dbid=8933">series homepage</A> +</P> +<A NAME="toc21"></A> +<H2>Extending the resource grammar API</H2> +<P> +Sooner or later it will happen that the resource grammar API +does not suffice for all applications. A common reason is +that it does not include idiomatic expressions in a given language. +The solution then is in the first place to build language-specific +extension modules, like <CODE>ExtraGer</CODE>. +</P> +<A NAME="toc22"></A> +<H2>Using parametrized modules</H2> +<A NAME="toc23"></A> +<H3>Writing an instance of parametrized resource grammar implementation</H3> +<P> +Above we have looked at how a resource implementation is built by +the copy and paste method (from English to German), that is, formally +speaking, from scratch. A more elegant solution available for +families of languages such as Romance and Scandinavian is to +use parametrized modules. The advantages are +</P> +<UL> +<LI>theoretical: linguistic generalizations and insights +<LI>practical: maintainability improves with fewer components +</UL> + +<P> +Here is a set of +<A HREF="http://www.cs.chalmers.se/~aarne/geocal2006.pdf">slides</A> +on the topic. +</P> +<A NAME="toc24"></A> +<H3>Parametrizing a resource grammar implementation</H3> +<P> +This is the most demanding form of resource grammar writing. +We do <I>not</I> recommend the method of parametrizing from the +beginning: it is easier to have one language first implemented +in the conventional way and then add another language of the +same family by aprametrization. This means that the copy and +paste method is still used, but at this time the differences +are put into an <CODE>interface</CODE> module. +</P> +<A NAME="toc25"></A> +<H2>Character encoding and transliterations</H2> +<P> +This section is relevant for languages using a non-ASCII character set. +</P> +<A NAME="toc26"></A> +<H2>Coding conventions in GF</H2> +<P> +From version 3.0, GF follows a simple encoding convention: +</P> +<UL> +<LI>GF source files may follow any encoding, such as isolatin-1 or UTF-8; + the default is isolatin-1, and UTF8 must be indicated by the judgement +<PRE> + flags coding = utf8 ; +</PRE> + in each source module. +<LI>for internal processing, all characters are converted to 16-bit unicode, + as the first step of grammar compilation guided by the <CODE>coding</CODE> flag +<LI>as the last step of compilation, all characters are converted to UTF-8 +<LI>thus, GF object files (<CODE>gfo</CODE>) and the Portable Grammar Format (<CODE>pgf</CODE>) + are in UTF-8 +</UL> + +<P> +Most current resource grammars use isolatin-1 in the source, but this does +not affect their use in parallel with grammars written in other encodings. +In fact, a grammar can be put up from modules using different codings. +</P> +<P> +<B>Warning</B>. While string literals may contain any characters, identifiers +must be isolatin-1 letters (or digits, underscores, or dashes). This has to +do with the restrictions of the lexer tool that is used. +</P> +<A NAME="toc27"></A> +<H2>Transliterations</H2> +<P> +While UTF-8 is well supported by most web browsers, its use in terminals and +text editors may cause disappointment. Many grammarians therefore prefer to +use ASCII transliterations. GF 3.0beta2 provides the following built-in +transliterations: +</P> +<UL> +<LI>Arabic +<LI>Devanagari (Hindi) +<LI>Thai +</UL> + +<P> +New transliterations can be defined in the GF source file +<A HREF="../src/GF/Text/Transliterations.hs"><CODE>GF/Text/Transliterations.hs</CODE></A>. +This file also gives instructions on how new ones are added. +</P> + +<!-- html code generated by txt2tags 2.4 (http://txt2tags.sf.net) --> +<!-- cmdline: txt2tags -\-toc Resource-HOWTO.txt --> +</BODY></HTML> |