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Automated Filipino Verbal Sentence Evaluator<br />
Jennefer B. Jore<br />
Associate Software Engineer<br />
Cybergate 1, Robinson’s Pioneer,<br />
Boni Ave., Manadaluyong<br />
Philippines<br />
jennefer.b.jore<br />
@yaccenture.com<br />
Ana Ruby B. Ramos<br />
Associate Software Engineer<br />
Cybergate 1, Robinson’s Pioneer,<br />
Boni Ave., Manadaluyong<br />
Philippines<br />
mam.ana.ruby.r.cordero<br />
@accenture.com<br />
Qurrata-Ayn K. Karim<br />
3rd author's affiliation<br />
1st line of address<br />
2nd line of address<br />
Telephone number, incl. country code<br />
Ayn_karim@yahoo.com<br />
Erlyn Q. Maguilimotan<br />
Faculty,<br />
Computer Science Dept.<br />
College of Science and Information<br />
Technology<br />
Ateneo De Zamboanga University<br />
erlynqm@yahoo.com<br />
Ebony C. Domingo<br />
Chairperson,<br />
Computer Science Dept.<br />
College of Science and Information<br />
Technology<br />
Ateneo De Zamboanga University<br />
domingoeboc@yahoo.com<br />
ABSTRACT<br />
Grammar acquisition is an important part of language acquisition<br />
and learning for human beings. Many projects have been designed<br />
to assist in the grammar development of people by having<br />
automated checking of grammars both for fixed word order and<br />
free word order languages. The Filipino language is a free word<br />
order language. It exhibits the problem of discontinuous<br />
constituents. Several approaches used to treat this problem use a<br />
hierarchical syntactic structure that resulted to parsing and<br />
processing delays. One approach that also treats this problem<br />
called Tagalog Free-Word Order (TagFWO) Parser uses a flat<br />
syntactic structure. This approach is able to solve the problem of<br />
discontinuous constituents syntactically. However, the semantic<br />
side is not treated by this approach. The aim of this research then<br />
is to develop a system that evaluates a Filipino verbal sentence by<br />
checking the syntactic structure and semantic relation of the<br />
constituents of the sentence.<br />
The Automated Filipino Verbal Sentence Evaluator is a system<br />
capable of evaluating Filipino verbal sentences based on its<br />
grammar. It uses a Parser in checking the grammar structure, and<br />
the Lexical Functional Grammar (LFG) formalism for the<br />
grammar relation. Grammar structure takes into account the<br />
syntax of the sentence by verifying if such sentence structure<br />
valid in the system. Grammar relation considers the functional<br />
relationship of each constituent in the sentence by checking if the<br />
doer in the sentence has the capability to do such action.<br />
The system is trained on a set of Filipino 33 verbal and nonverbal<br />
sentences (grammatical and ungrammatical). The results<br />
showed that the grammatical verbal sentences were all evaluated<br />
properly with their corresponding detailed user evaluation<br />
feedback. The grammatical non-verbal and ungrammatical<br />
sentences are rejected and outputted a corresponding error<br />
message.<br />
The method developed in this research has resolved issues on<br />
syntactic and semantic relations in tagalong verbal sentences.<br />
However the issues of lexical ambiguities and deeper semantic<br />
interpretations have not yet been included in this research. This<br />
study can further be enhanced to embrace a more complex verbal<br />
system of the Filipino language considering other parts of speech.<br />
General Terms<br />
Algorithms, Languages.<br />
Keywords<br />
Grammar checker, Filipino, natural language processing, artificial<br />
intelligence, text processing.<br />
1. INTRODUCTION<br />
Language systems consist of words arranged in certain learned<br />
ways (grammar and syntax). Internationalization of language<br />
systems is developed through recognition of syntactic structures<br />
or grammar of a language. Syntactic analysis is the process of<br />
determining the syntactic structure of a sentence according to<br />
grammar rules. This analysis is vital for the recognition of the<br />
grammatical correctness of a sentence [14].<br />
Syntactic analysis is subdivided into structure and relation. One<br />
major application of structural syntactic analysis is parsing. This<br />
method is the decomposition of scanned tokens in an input stream<br />
(a sentence in a language) into components based on phrase<br />
structure grammar rules. Grammar is defined as a system of rules<br />
and principles that determine the formal, legal and semantic<br />
properties of sentences [5] and the description of the signals<br />
which lead to the understanding of a language. Most studies<br />
conducted in the field of syntactic analysis are concentrated on<br />
parsing algorithms.<br />
Parsing algorithms are given higher priority than grammatical<br />
relation is because researchers in this field are seeking a universal<br />
model on syntax for both free and fixed word order languages.<br />
53
However, fixed word order languages are considered in most<br />
investigations [9].<br />
Fixed word order languages are languages that have a strict<br />
ordering of constituents [3] and is said to be configurational,<br />
while free word order languages do not follow any rule for the<br />
ordering of the constituents and is said to be non-configurational.<br />
Non-configurational means the verb, as the head of the sentence<br />
structure, along with the other constituents in the structure can be<br />
treated as sisters [7]. In a configurational setting the verb and<br />
other constituents cannot be treated as sisters. A separate verb<br />
node is required. Current approaches on free word order<br />
languages are based the configurational approach and thus,<br />
resulting to problems of capturing discontinuous constituents<br />
which are present in free word order languages [3].<br />
Current treatment to this problem is already available. One<br />
approach to this problem is scrambling approach which involves<br />
transformations of a constituent from its original position to other<br />
positions until the right position is found [3]. However, this<br />
approach creates parsing delays due to searching of the adjacent<br />
constituents. Another approach is the sortal hierarchy of types,<br />
which was modeled using the German language [11].<br />
Unfortunately, this approach cannot be applied to Filipino<br />
because it is unsuitable for representing adjacent constituents.<br />
Another approach is the discontinuous dependency parsing which<br />
was applied to Russian and Latin [1]. This approach is applicable<br />
to other languages; however, it is time consuming. It backtracks<br />
and finds an alternative solution thus, exhibits non-determinism<br />
due to the lack of a predictive capability [3].<br />
One research in the Philippines on syntactic analysis is called<br />
Tagalog Free Word Order (TagFWO) Parser by Editha D.<br />
Dimalen [3]. TagFWO Parser is a web-based implementation of a<br />
new technique to address the problem of discontinuous<br />
constituents in a free word order language, Tagalog. It uses flat<br />
syntactic structure that differs from the current approaches that<br />
uses a hierarchical syntactic structure. It uses the concept of Head<br />
Specifier and Head Complement rules to handle the constituency<br />
of tagalong language. It is appropriate for Tagalog language and<br />
require less computing time in contrast to other existing approach.<br />
However, the above-mentioned approaches are focused on the<br />
syntactic structure of the sentences and less on the grammatical<br />
relations. A study by Kroeger [7] showed the insufficiency of<br />
phrase structure rules to capture the syntactic relations and the<br />
importance played by grammatical relations for the Filipino<br />
language. Filipino is the national language of the Philippines. This<br />
language is characterized to be non-configurational. As nonconfigurational,<br />
Filipino does not follow fixed ordering of words<br />
in sentence constructions. Thus, phrase structure rules are not<br />
considered to be sufficient to address the non-configurationality<br />
of the language.<br />
Syntactic relationships and grammatical relations in Filipino are<br />
signified by case markings and verbal affixations [8]. These<br />
syntactic attributes contribute working out what is to be means in<br />
a sentence. The affixations in the Filipino language signify<br />
semantic criteria and categories. Phrasal structures do not succeed<br />
in understanding lexical structures in words but only<br />
componential functions within phrases [6].<br />
Grammar formalism is needed in order to capture syntactic<br />
relationships and grammatical relations of each constituent in a<br />
sentence in any natural language like Filipino. The Lexical<br />
Functional Grammar (LFG) is able to capture both of these<br />
syntactic attributes. Dimalen [6] made use of Head-driven Phrase<br />
Structure Grammar (HPSG) formalism. However, according to<br />
the author, LFG is simpler while retaining the same capabilities of<br />
HPSG. This research then developed an automated grammar<br />
checker for Filipino verbal sentences, which used LFG grammar<br />
formalism.<br />
2. FILIPINO VERBAL SENTENCE<br />
Filipino verbal sentences are sentences that contain a verb or verb<br />
form in the predicate position. The verbal form of the predicate<br />
determines the role of the noun(s) in the sentence. This depends<br />
on the affix in the verb which tell whether the noun is being an<br />
actor, object, instrument, etc.<br />
One interesting feature of the Filipino language is its focus<br />
system. This means that the role of the noun in focus is reflected<br />
in the verb. Focus is the feature of a verbal predicate that<br />
determines the semantic relationship between a predicate verb and<br />
its topic [12]. There are two types of focus that occur on a basic<br />
Filipino sentence: Actor-focus, the focus is on the actor or doer,<br />
and Goal-focus, does not focus on the actor. There are different<br />
classes of goal-focus. However, Schachter and Otanes [12]<br />
pointed out that only two from these classes are found in basic<br />
Filipino sentence: Object focus, and Directional-focus. The use of<br />
this different focus is based on their affixes.<br />
The verb is based on the use of affixes. The affix is a way of<br />
packaging in some extra information into a word. Filipino uses<br />
affixes in a similar way to indicate tenses of a verb, if an action is<br />
completed or not. In addition to this, Filipino uses affixes to<br />
indicate the role of the focus of the sentence. In other words,<br />
affixes are used to determine what the focus is doing in the<br />
sentence.<br />
2.1 LFG as a grammar checker<br />
A grammar checker was developed to address the problem on<br />
word order, subject-verb agreement and pragmatically in correct<br />
constituent orders of German sentences. This project made use of<br />
LFG and supplemented with rule components for analysis of<br />
ungrammatical input. LFG is composed of constituent-structure<br />
containing the linear hierarchical constituent order and functional<br />
structure representing functional relations and grammatical<br />
features by means of attribute value matrices. Having rule-based<br />
grammar checker with LFG, this project was able to parse<br />
unrestricted input and identify correct errors. However,<br />
orthography and morphological error identified are still<br />
unresolved [4].<br />
LFG has two structures for representing different levels of<br />
linguistics information: constituent structure (c-structure) and the<br />
functional structure (f-structure). The c-structure in LFG<br />
represents the external structure of a sentence in the form of a<br />
phrase structure tree [15]. It shows the syntactic constituents of<br />
the sentence. It relies on the grammar rules defined by the LFG. It<br />
is the more concrete level of linear and hierarchical organization<br />
54
of words into phrases [2]. It contains lexical and functional<br />
categories. A sample c-structure is shown in Figure 1 applying<br />
phrase structure rules for the sentence “natulog ang bata” .<br />
checks for the capability of the doer to do the task which is the<br />
verb. It checks the lexical entry of the verb if such object is<br />
accepted to it. It also checks the relationship between the two<br />
nouns through the verb. Since the verb accepts an object and the<br />
doer has the capability to do the action based from the lexical<br />
entry, then, f-structure considers this sentence as grammatically<br />
correct.<br />
Figure1. Sample c-structure with Functional Schemata<br />
The functional schemata ( SUBJ) = and = show in symbols<br />
the role of each string play in a sentence (Mangulimotan, 2001). f-<br />
structure does not have direct mapping from cstructure. It is<br />
constructed from instantiation. Thus, the arrows symbols assume<br />
referential values that point to their values () and to which<br />
immediately dominates them () [10].<br />
3. SYSTEM WORKFLOW<br />
The overall flow of the system is shown in figure 3. An input<br />
sentence is passed on to the Lexical Analyzer module. There are<br />
three applications that process the sentence in this module. The<br />
first application is called Tokenization which separates each word<br />
of the sentence as a unique entity called token. Once tokenized,<br />
the first token which should be the verb, is passed on to the<br />
second application called Word Stemming. This application<br />
determines the root word of the verb by extracting the affixes. At<br />
the same time, it checks the validity of the root word form using<br />
the lexicon. Based from the extracted affix, the focus type of the<br />
sentence can be determined [13]. The remaining tokens are also<br />
checked if such word exists in the lexicon. The final application<br />
for this module is Tagging. Each token is tagged with the proper<br />
part-of-speech tags which are passed on to the parser.<br />
The f-structure models the internal structure of a language and the<br />
functional roles of each constituent or word order in producing<br />
the meaning of the sentence [2].Each word is designated a set of<br />
categories like subject, object, topic, focus, aspect, case, number,<br />
gender, and other important lexical attributes. This is how f-structure<br />
checks the grammaticality sentence “bumili ang bata ng isda” ( Figure 2).<br />
Figure 2. Sample f-structure<br />
The verb Bumili is considered to be in actor focus since it has the<br />
affix um and thus, making the actor as the subject of the sentence.<br />
The determiner ang determines the subject. The noun bata which<br />
is preceded by the determiner ang and the focus signifies the term<br />
as the subject. Thus from the relationship alone of these three<br />
constituents, the f-structure can immediately identify the subject.<br />
The verb Bumili is an actor focus for it has the affix um. As a rule,<br />
actor focus requires an actor to make the sentence complete. The<br />
object is an optional in the sentence. However, in this sentence, an<br />
object phrase is included. To check if the phrase is an object, a<br />
determiner ng is checked after the subject. The noun isda which is<br />
preceded by ng signifies the term as the object. f-structure does<br />
not only rely on checking the subject and doer rather it also<br />
Figure 3. Architectural Design<br />
The parser verifies the grammar structure through the grammarrule<br />
specified in the system. It is the syntactic structure that is<br />
evaluated by the parser first through the grammar syntax rules<br />
provided by the system. The semantic side is evaluated by Lexical<br />
Functional Grammar (LFG).<br />
LFG evaluates the semantic of the sentence by means of<br />
grammatical relations. Each word in the sentence has their<br />
respective lexical information defined in the lexicon. After LFG<br />
evaluates, the systems outputs a user feedback that states the<br />
evaluation process of the system.<br />
4. RESULTS AND DISCUSSION<br />
Filipino verbal sentence is the main study of this research. The<br />
following rules that were adopted in different Balarilang Filipino<br />
55
ooks were used as a basis for determining grammatically correct<br />
and wrong Filipino verbal sentences.<br />
Figure 4. Grammar Rules<br />
This research initially made use of 16 verbs and 38 nouns chosen<br />
randomly from the Handbook of Tagalog Verbs by Teresita V.<br />
Ramos [12]. These were made part of the lexicon. The system<br />
was tested and evaluated using different Filipino verbal and nonverbal<br />
sentences. There were seven (7) grammatically correct<br />
Filipino verbal sentences that was successfully evaluated by the<br />
system. Taking all the possible orderings of the 7 sentences, it<br />
resulted to thirty-three (33) combinations in all due to free-word<br />
ordering. The system has been able to evaluate the sample<br />
sentences. Grammatically correct verbal sentences were<br />
acknowledged with a detailed evaluation as an output of the<br />
system while grammatically wrong sentences were also<br />
acknowledged and given with the necessary information for being<br />
incorrect.<br />
5. RECOMMENDATIONS<br />
The Automated Filipino Verbal Sentence Evaluator has resolved<br />
the issues on syntactic and semantic relations. However, the<br />
issues of lexical ambiguities and deeper semantic interpretations<br />
have not yet been included in this research. But, with LFG’s<br />
ability of employing semantic relation rules, it is possible to<br />
resolve the issues on lexical ambiguities and deeper semantic<br />
interpretations. However, this requires changes in the semantic<br />
rule and is subject to further investigations.<br />
This study can further be enhanced to embrace a more complex<br />
verbal system of the Filipino language. Other Filipino parts of<br />
speech may also be considered as an additional scope to the study.<br />
In line with this, an automated Filipino essay evaluator can be<br />
developed through this advance studies.<br />
Kroeger [7] has said that Philippine-type languages exhibit<br />
structural similarities. This means that it is possible for the system<br />
to be also used for other Philippines languages and requires only<br />
additional entries in the lexicon. Moreover, this research has made<br />
a very significant contribution in the field of Natural Language<br />
Processing especially in the different researches and studies<br />
conducted for the Filipino language.<br />
6. REFERENCES<br />
[1] Covington, M.Discontinuous Dependency Parsing of Free<br />
and Fixed Word Order. Available:<br />
http://www.ai.uga.edu/ftplib/ai_reports/reports.txt, 1994.<br />
[2] Dalrymple,M. A Lexical Functional Grammar. Available :<br />
http://users.ox.ac.uk/~cpgl0015/lfg.pdf, 2001.<br />
[3] Dimalen, E. Algorithm for Consituent Structures of Tagalog.<br />
MS Thesis, De Lasalle University Professional Schools, Inc.<br />
Manila, Philippines, 2003.<br />
[4] Fortmann, C.and Frost, M. An LFG Grammar Checker for<br />
CALL. Available: ftp://www.ims.uniuttgart.de/pub/Users/forst/Fortmann:Forst-ICALL04.pdf<br />
[5] Fries, P.The 31st International Systematic Functional<br />
Congress. Doshisha University,Kyoto, Japan.<br />
vailable:http://www1.doshisha.ac.jp/~mtatsuki/ISFC31/pages<br />
/abstract_plenary.pdf, 2004.<br />
[6] Hoopman, H., Sportiche, D. and Stabler, E.. An Introduction<br />
to Syntactic Analysis and Theory. Available:<br />
http://www.linguistics.ucla.edu/people/sportiche/isat.pdf,<br />
2002.<br />
[7] Kroeger, P..Phrase Structure and Grammatical Relations in<br />
Tagalog.Dissertations in Linguistics. Stanford, CA: Center<br />
for the Study of Language and Information.xiv,240p, 1993.<br />
[8] Lupyan, G. Modelling Syntactic Devices: An Explanation of<br />
Language Evolution from Connectinist and Memetic<br />
Perspectives.<br />
Available:http://www.isr/uiuc.edu/~amag/langev/paper/lupya<br />
n02modeling.html, 2002.<br />
[9] Maegard, B.Machine Translation.<br />
Available:http://www.cs.uregina.ca/Research.Techreports/95<br />
09.ps, 2002.<br />
[10] Manguilimotan, E.(2001). Syntactic Representation of<br />
Tausug Verbal Sentences. MS Thesis, MSU-Iligan Institute<br />
of Technology, Iligan City, Philippines, 2001.<br />
[11] Oliva, K.The Proper Treatment of Word order in HPSG.In<br />
the Proceedings of the 14 th International Conference on<br />
Computational Linguistics, Nantes.<br />
Available:http//www.acl.ldc.upenn.edu/C/C92?c92-<br />
1031.pdf, 1992.<br />
[12] Ramos, T.Handbook of Tagalog Verbs. University of Hawaii<br />
Press, 320 pp., 1986.<br />
[13] Schachter, P. & Otanes, F. Tagalog Grammar Reference.<br />
University of California Press. Berkeley, CA, 1972.<br />
[14] Tablante, N..The Predictive Value of Knowledge in<br />
Grammar in the Writing Proficiency of the Freshmen<br />
Engineering Students, 1997.<br />
[15] Wong, S.(2001). Lexical Functional Grammar.<br />
Available:<br />
http://www.fi.muni.cz/usr/wong/teaching/mt/notes/node15.html.is<br />
o-8859-1, 2001.<br />
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