Natural Language Processing Laboratory Computer Science Essay

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ABSTRACT

As the premiere human language technology center in the country, we present the diverse research activities of the Natural Language Processing Laboratory of the College of Computer Studies, De La Salle University, focusing mainly on the projects that we have embarked on.  These projects include the formal representation of human languages and the processes involving these languages.  Language representation entails the development of language resources such as lexicons and corpora for various human languages including Philippine languages, across various forms such as text, speech and video files.  Applications on languages that we have worked on include Machine Translation, Question-and-Answering Systems, Information Extraction, Natural Language Generation, Automated Text Summarization and Simplification, and Language Education.   These applications provide the current human language interface for communication, searching, and learning, to name a few.

Keywords: Natural Language Processing, Human Language Technology

INTRODUCTION

There are more than 6000 living natural languages in the world. In the Philippines alone, there are 168 natively spoken languages [24]. Natural language processing (NLP or Human language technology) provides modern technologically-based solutions to bridge the gap across language. It is concerned with the interactions between humans and computers through natural languages.

Main drivers of NLP research include the need for intelligent natural interfaces and the problem of information overload. Intelligent natural interfaces should allow the user to communicate with the machine through natural language.

Since information is readily available through various means especially with the advent of the internet, there is also information overload [11]. NLP provides an interface that automatically filters relevant information for the user.

Sub-areas in NLP include natural language understanding (NLU), natural language generation (NLG), information retrieval, information extraction, machine translation and question-answering. Interleaving with these applications are the computational layers of language resources necessary for automatic representation and processing of human languages.

The Natural Language Processing Laboratory of the College of Computer Studies, De La Salle University, has endeavored to address both the language resources and the corresponding computational processes. We will discuss some of these projects and the future directions for NLP research in the country.

LANGUAGE RESOURCES

Though linguistic information on Philippine languages are available, as of yet, the focus has been on theoretical linguistics and little has been done on the computational aspects. Since these language resources are the major building blocks in doing natural language processing, it is imperative that these be addressed. We report here our attempts in the manual construction of these language resources such as the lexicon, morphological information, grammar, and the corpora which were literally built from almost non-existent digital forms. Due to the inherent difficulties of manual construction, we also discuss our experiments on various technologies for automatic extraction of these resources to handle the intricacies of the Filipino language, designed with the intention of using them for various language technology applications.

One of the main resources of any system that involves natural language is the list of words which is referred to as the lexicon. These words would have associated information depending on the purpose of the application. For instance, for automatic translation of documents from one natural language to another, a bi-directional lexicon is essential. Currently, the English-Filipino lexicon contains 23,520 English and 20,540 Filipino word senses with information on the part of speech and co-occurring words, which is based on the dictionary of the Komisyon sa Wikang Filipino. Additional information such as synsetID from Princeton WordNet were integrated into the lexicon [30]. As manually populating the database with the synsetIDs from WordNet is tedious, automating the process through the SUMO (Suggested Upper Merged Ontology) as an InterLingual Index (ILI) is now being explored.

Initial work on the manual collection of documents on Philippine languages has been done through the funding from the National Commission for Culture and the Arts considering four major Philippine Languages namely, Tagalog, Cebuano, Ilocano and Hiligaynon with 250,000 words each and the Filipino sign language with 7,000 signs [36]. Computational features include word frequency counts and a concordancer that allows viewing co-occurring words in the corpus.

Aside from possibilities of connecting the Philippine islands and regions through language, we are also aiming at crossing boundaries of time [35]. An unexplored but equally challenging area is the collection of historical documents that will allow research on the development of the Philippine languages through the centuries. An interesting piece of historical information is in Doctrina Christiana, the first ever published work in the country in 1593 which shows the translation of religious material in the local Philippine script, the Alibata, and Spanish. A sample page is shown in Figure 1 (courtesy of the University of Sto. Tomas Library, 2007).

Figure 1: Sample Page: Doctrina Christiana (courtesy of the University of Sto. Tomas Library, 2007)

Attempts are being made to expand on these language resources and to complement manual efforts to build these resources. Automatic methods and social networking are the two main options currently being considered.

Language Resource Builder

Automatic methods for bilingual lexicon extraction, named-entity extraction, and language corpora are also being explored to exploit on the resources available on the internet. These automatic methods are discussed in detail in this section.

An automated approach of extracting bilingual lexicon from comparable, non-parallel corpora was developed for English as the source language and Tagalog as the target language, the latter having limited electronic linguistic resources available [39]. We combined approaches from previous researches which only concentrated on context extraction, clustering techniques, or usage of part of speech tags for defining the different senses of a word, and ranking has shown improvement to overall F-measure from 7.32% to 10.65% within the range of values from previous studies. This is despite the use of limited amount of corpora of 400k and seed lexicon of 9,026 entries in contrast to previous studies of 39M and 16,380, respectively.

The NER-Fil is a Named Entity Recognizer for Filipino Text [29]. This system automatically identifies and stores named-entities from documents, which can also be used to annotate corpora with named-entity information. Using machine learning techniques, named-entites are also automatically classified into appropriate categories such as person, place, and organization.

AutoCor is an automatic retrieval system for documents written in closely-related languages [15]. Experiments have been conducted on four closely-related Philippine languages, namely: Tagalog, Cebuano and Bicolano. Input documents are matched against the n-gram language models of relevant and irrelevant documents. Using common word pruning to differentiate between the closely-related Philippine languages, and the odds ratio query generation methods, results show improvements in the precision of the system.

Although automatic methods can facilitate the building of the language resources needed for processing natural languages, these automatic methods usually employ learning approaches that would require existing language resources as seed or learning data sets.

Online Community for Corpora Building

PALITO is an online repository of the Philippine corpus [36]. It is intended to allow linguists or language researchers to upload text documents written in any Philippine language, and would eventually function as corpora for Philippine language documentation and research. Automatic tools for data categorization and corpus annotation are provided by the system. The LASCOPHIL (La Salle Corpus of Philippine Languages) Working Group is assisting the project developers of PALITO in refining the mechanics for the levels of users and their corresponding privileges for a manageable monitoring of the corpora. Videos on the Filipino sign language can also be uploaded into the system. Uploading of speech recordings will be considered in the near future, to address the need to employ the best technology to document and systematically collect speech recordings of nearly-extinct languages in the country. This online system capitalizes on the opportunity for the corpora to expand faster and wider with the involvement of more people from various parts of the world. This is also to exploit on the reality that many of the Filipinos here and abroad are native speakers of their own local languages or dialects and can largely contribute to the growth of the corpora on Philippine languages.

LANGUAGE TOOLS

Language tools are applications that support linguistic research and processing of various language computational layers. These include lexical units, to syntax and semantics. Specifically, we have worked on the morphological processes, part of speech tagging and parsing. These processes usually employ either the rule-based approach or the example-based approach. In general, rule-based approaches capture language processes by formally capturing these processes which would require consultations and inputs from linguists. On the other hand, example-based approaches employ machine learning methodologies where automatic learning of rules is performed based on manually annotated data that are done also by linguists.

Morphological Processes

In general, morphological processes are categorized as morphological analysis or morphological generation. Morphological analyzers (MA) are automated systems that derive the root word of a transformed word, and identify the affixes used and the changes in semantics due to the word transformation. In this way, root words and their derivatives do not have to be stored in the lexicon. On the other hand, morphological generators transform a root word into the surface form given the desired word usage.

We have tested both rule-based and example-based approaches in developing our MA and MG. Rule-based morphological analysis in the current methods, such as finite-state and unification-based, are predominantly effective for handling concatenative morphology (e.g. prefixation and suffixation), although some of these techniques can also handle limited non-concatenative phenomena (e.g. infixation and partial and full-stem reduplication) which are largely used in Philippine languages. TagMA [21] uses a constraint-based method to perform morphological analysis that handles both concatenative and non-concatenative morphological phenomena, based on the optimality theory framework and the two-level morphology rule representation. Test results showed 96% accuracy. The 4% error is attributed to d-r alteration, an example of which is in the word lakaran, which is from the root word lakad and suffix -an, but d is changed to r. Unfortunately, since all candidates are generated, and erroneous ones are later eliminated through constraints and rules, time efficiency is affected by the exhaustive search performed.

To augment the rule-based approach, an example-based approach was explored by extending Wicentowski's Word Frame model through learning of morphology rules from examples. In the WordFrame model, the seven-way split re-write rules composed of the canonical prefix/beginning, point-of-prefixation, common prefix substrings, internal vowel change, common suffix substring, point-of-suffixation, and canonical suffix/ending. Infixation, partial and full reduplication as in Tagalog and other Philippine languages are improperly modeled in the WordFrame model as point-of-prefixation as in the word (hin)-intay which should have been modeled as the word hintay with infix -in-. Words with an infix within a prefix are also modeled as point-of-prefixation as in the word (hini-)hintay which should be represented as infix -in in partial reduplicated syllable hi-. In the revised WordFrame model [10], the non-concatenative Tagalog morphological behaviors such as infixation and reduplication are modeled separately and correctly. Unfortunately, it is still not capable of fully modeling Filipino morphology since some occurrences of reduplication are still represented as point-of-suffixation for various locations of the longest common substring. There are also some problems in handling the occurrence of several partial or whole-word reduplications within a word. Despite these problems, the training of the algorithm that learns these re-write rules from 40,276 Filipino word pairs derived 90% accuracy when applied to an MA. The complexity of creating a better model would be computationally costly but it would ensure an increase in performance and reduced number of rules.

Work is still to be done on exploring techniques and methodologies for morphological generation (MG). Although it could be inferred that the approaches for MA can be extended to handle MG, an additional disambiguation process is necessary to choose the appropriate output from the many various surface form of words that can be generated from one underlying form.

Part of Speech Tagging

One of the most useful information in the language corpora are the part of speech tags that are associated with each word in the corpora. These tags allow applications to perform other syntactic and semantic processes. Firstly, with the aid of linguists, we have come up with a revised tagset for Tagalog, since a close examination of the existing tagset for languages such as English showed the insufficiency of this tagset to handle certain phenomena in Philippine languages. Manual tagging of corpora has allowed us to perform automatic experiments on some approaches for tagging for Philippine languages namely MBPOST, PTPOST4.1, TPOST and TagAlog, each one exploring on a particular approach in tagging such as memory-based POS, template-based and rule-based approaches. A study on the performance of these taggers showed accuracies of 85, 73, 65 and 61%, respectively [32].

Language Grammars

Grammar checkers are some of the applications where syntactic specification of languages is necessary. SpellCheF is a spell checker for Filipino that uses a hybrid approach in detecting and correcting misspelled words in a document [8]. Its approach is composed of dictionary-lookup, n-gram analysis, Soundex and character distance measurements. It is implemented as a plug-in to OpenOffice Writer. Two spelling rules and guidelines, namely, the Komisyon sa Wikang Filipino 2001 Revision of the Alphabet and Guidelines in Spelling the Filipino Language, and the Gabay sa Editing sa Wikang Filipino rulebooks, were incorporated into the system. SpellCheF consists of the lexicon builder, the detector, and the corrector; all of which utilized both manually formulated and automatically learned rules to carry out their respective tasks.

FiSSAn, on the other hand, is a semantics-based grammar checker. This software is also a plug-in to Open Office. Lastly, PanPam is an extension of FiSSAn that also incorporates a dictionary-based spell checker [4].

These systems make use of the rule-based approach. To complement these systems, an example-based approach is considered through a grammar rule induction method [1]. Constituent structures are automatically induced using unsupervised probabilistic approaches. Two models are presented and results on the Filipino language show an F1 measure of greater than 69%. Experiments revealed that the Filipino language does not follow a strict binary structure as English, but is more right-biased.

A similar experiment has been conducted on grammar rule induction for the automatic parsing of the Philippine component of the International Corpus of English (ICE-PHI) [19]. Automatic part of speech (POS) tagging will first be performed using the tagger that was trained and used on the Great Britain component of the ICE.  Differences in expected mark-up syntax and lexical items might surface during POS tagging; thus, requiring additional editing of text documents.  After automatic tagging, manual post editing will be performed to correct some mistagging expected, some of which would be due to the inclusion of indigenous words, such as Tagalog words in the ICE-PHI texts.  The POS tagger will be retrained using the refined data for re-processing.  Constituent rule induction is performed from manually syntactically bracketed files from the ICE-PHI, and will be used to parse the rest of the corpus. Manual post editing of the parse will be performed. The development of such tools will directly benefit the descriptive and applied linguistics of Philippine English, as well as other Englishes, in particular, those language components in the ICE.

LANGUAGE APPLICATIONS

Various applications have been created to cater to different needs. Needs range from summarizing to question answering and from domains of education to the arts. Below are some of the language technology applications that have been developed at the NLP Laboratory, College of Computer Studies, De La Salle University.

Machine Translation

The Hybrid English-Filipino Machine Translation (MT) System is a three-year project (with funding from the PCASTRD, DOST), which involves a multi-engine approach for automatic language translation of English and Filipino [33]. The MT engines explore on approaches in translation using a rule-based method and two example-based methods. The rule-based approach requires the formal specification of the human languages covered in the study and utilizes these rules to translate the input. The two other MT engines make use of examples to determine the translation. The example-based MT engines have different approaches in their use of the examples (which are existing English and Filipino documents), as well as the data that they are learning. Refer to Figure 2 for the Architectural Diagram.

The system accepts as input a sentence or a document in the source language and translates this into the target language. If source language is English, the target language is Filipino, and vise versa. The input text will undergo preprocessing that will include POS tagging and morphological analysis. After translation, the output translation will undergo natural language generation including morphological generation. Since each of the MT engines would not necessarily have the same output translation, an additional component called the Output Modeler was created to determine the most appropriate among the translation outputs [23]. There are ongoing experiments on the hybridization of the rule-based and the template-based approaches where transfer rules and unification constraints are derived [20].

One of the main problems in language processing most especially compounded in machine translation is finding the most appropriate translation of a word when there are several meanings of source words, and various target word equivalents depending on the context of the source word. One particular study that focuses on the use of syntactic relationships to perform word sense disambiguation has been explored [17]. It uses an automated approach for resolving target-word selection, based on "word-to-sense" and "sense-to-word" relationship between source words and their translations, using syntactic relationships (subject-verb, verb-object, adjective-noun). Using information from a bilingual dictionary and word similarity measures from WordNet, a target word is selected using statistics from a target language corpus. Test results using English to Tagalog translations showed an overall 64% accuracy for selecting word translation.

Rule-based Machine Translation Engine

Example-Based

MT1

POS Tagger &

Morph A/G

Rule-Based

MT

Example-Based

MT2

User Interface

Output Modeler

Source

Language

Target

Language

Lexicon & Corpora

Figure 2: The Architecture of the Hybrid English-Filipino

Machine Translation System

NLP Research in CCS -- The Now

With several faculty members being involved in the

The rule-based MT builds a database of rules for language representation and translation rules from linguists and other experts on translation from English to Filipino and from Filipino to English. We have considered lexical functional grammar (LFG) as the formalism to capture these rules. Given a sentence in the source language, the sentence is processed and a computerized representation in LFG of this sentence is constructed. An evaluation of how comprehensive and exhaustive the identified grammar is to be considered. Is the system able to capture all possible Filipino sentences? How are all possible sentences to be represented since Filipino exhibits some form of free word order in sentences? The next step is the translation step, that is, the conversion of the computerized representation of the input sentence into the intended target language. After the translation process, the computerized representation of the sentence in the target language will now be outputted into a sentence form, or called the generation process. Although it has been shown in various studies elsewhere and on various languages that LFG can be used for analysis of sentences, there is still a question of whether it can be used for the generation process. The generation involves the outputting of a sentence from a computer-based representation of the sentence. This is part of the work that the group intends to address.

The major advantage of the rule-based MT over other approaches is that it can produce high quality translation for sentence patterns that were accurately captured by the rules of the MT engine; but unfortunately, it cannot provide good translations to any sentence that go beyond what the rules have considered.

Corpus-based Machine Translation Engines

In contrast to the rule-based MT which requires building the rules by hand, the corpus-based MT system automatically learns how translation is done through examples found in a corpus of translated documents. The system can incrementally learn when new translated documents are added into the knowledge-base, thus, any changes to the language can also be accommodated through the updates on the example translations. This means it can handle translation of documents from various domains [2].

The principle of garbage-in-garbage-out applies here; if the example translations are faulty, the learned rules will also be faulty. That is why, although human linguists do not have to specify and come up with the translation rules, the linguist will have to first verify the translated documents and consequently, the learned rules, for accuracy.

It is not only the quality of the collection of translations that affects the overall performance of the system, but also the quantity. The collection of translations has to be comprehensive so that the translation system produced will be able to translate as much types of sentences as possible. The challenge here is coming up with a quantity of examples that is sufficient for accurate translation of documents.

With more data, a new problem arises when the knowledge-base grows so large that access to it and search for applicable rules during translation requires tremendous amount of access time and to an extreme, becomes difficult. Exponential growth of the knowledge-base may also happen due to the free word order nature of Filipino sentence construction, such that one English sentence can be translated to several Filipino sentences. When all these combinations are part of the translation examples, a translation rule will be learned and extracted by the system for each combination, thus, causing growth of the knowledge-base. Thus, algorithms that perform generalization of rules are considered to remove specificity of translation rules extracted and thus, reduce the size of the rule knowledge-base.

Text Summarization

SUMMER TXT automatically summarizes a document given the desired percentage of reduction [16]. It formally captures the information in the training data set and the relationships among these data using the rhetorical structure theory. Thus, the summarized text maintains coherence without having to resort to copying whole sentences from the original text. To add, deletion of an arbitrary amount of source material has the potential of losing essential information. Evaluation against existing commercially available software has shown that the output of SUMMER TXT is comparable to these systems. Unfortunately, the domain of the training and test data has been limited to one particular author and in one particular domain. Experiments on this approach for a wider range of authors and styles and their corresponding domains are yet to be performed.

Text Simplification

SimText is a text simplification system that accepts as input a medical document and transforms complex sentences into a set of equivalent simpler sentences with the goal of making the resulting text easier to read by some target group [14]. The simplification includes the use of easier to understand terminologies and shorter sentence constructs considering the specified reading level of the intended target users. The text simplification process identifies components of sentence that may be separated out, and transforms each of these into free-standing simpler sentences. Some nuances of meaning from the original text may be lost in the simplification process, since sentence-level syntactic restructuring can possibly alter the meaning of the sentence.

Educational Applications

On the field of education, some applications that we have developed include Kids Quest III, Picture Books, MesCh, Popsicle, and Automatic Essay Evaluator. Kids Quest is a tool that automatically generates the animation of a story based on the story inputted by the child [6]. This incorporates spelling and grammar checking features and rendering of the animation of the story inputted.

On a reverse process, Picture Books generates stories for children from an input of character and object stickers [26]. The child chooses the stickers (representing the characters and objects) and the system associates these objects to a (manually created) ontology and story pattern which is then generated into a story. On a sample screen shot, the left side of the screen is where the child has already chosen characters and is in the process of choosing objects. The right side of the screen shot will appear the generated story.

On the other hand, MesCH is a software that accepts children's stories and automatically generates multiple choice questions to test the child's reading comprehension [18]. The program rephrases parts of the story into 4W questions (who, what, when, where), sequence questions (which came first), and vocabulary questions. To illustrate, from a sentence in a story "Slimy tadpoles came out from the eggs", the system will generate the following possible stems:

What came out from the eggs?

Where did the slimy tadpoles come out?

In the sentence, "Slimy tadpoles came out from the eggs," what does the verb "came out" mean?

In the sentence, "Slimy tadpoles came out from the eggs," what does the adjective "slimy" mean?

The system considers principles in instructional assessment such as the formulation of 4W questions and the construction of distractors through the use of entries in WordNet that relate with the correct answer.

Popsicle is a software that identifies and corrects language errors committed by students while they are learning the English language [25]. The software initially assesses the English grammar proficiency of the learner based on an input document that was composed by the user, identifies the grammatical errors committed in the document, provides feedback and suggestions in natural language, and generates grammar lessons that are tailor fit to the individual needs of the learner. The learner is given opportunities to correct and learn from his mistakes. The software maintains a user model that tracks an individual learner's English grammar proficiency, his position and path toward acquiring English, the dialogue history containing the text generated by the system during the current tutorial session, the evaluation scores for each of the teaching strategies employed, and a concise log of explanations attempted by the system over the learning period of the user.

Automatic essay evaluator [12] automates the evaluation of large collections of essay-type documents using the latent semantic analysis (LSA) technique. Rule-based natural language parsing is used for the grammar checking of the input sentences, while LSA is used to evaluate the content. The system was trained on corpora containing pre-graded essays gathered from a particular high school class, which were graded by at least two human teachers according to three criteria: its mechanics, organization and content. Based on the tests performed, the system deviated from the human score by only 2.48%

Information Extraction

LegalTRUTHS performs automatic extraction of structured data from unstructured data; that is, from long textual documents to databases [11]. It aims to minimize the user's need of going through countless number and infinitely long legal documents and court decisions to extract key information about the case at hand. Based on the sample documents, a template for the database was developed through consultations with lawyers. The process follows the traditional approach wherein preprocessing of the input text is performed which includes text segmentation into different regions, detection of sentence boundaries, part of speech tagging and named entity recognition. Then text recognition is performed by applying the corresponding rules as needed to fill up the database. These include detection of noun and verb groups as a whole entity, normalization of the output, filtering of irrelevant information, co-reference resolution and extraction of the basic fields in the proposed template. The system also has an automatic evaluation module that uses longest common subsequence and the metrics precision, recall and f-measure to check the system's correctness. As a front-end application, the system also provides keyword search from the extracted fields. The matching entries provide links to the actual documents. Figure 3 shows a sample screen shot of the relevant information extracted into table form. Overall results show precision at 91%, recall at 99%, and F-measure at 95%.

Figure 3: Excerpt of Information Extracted by LegalTRUTHs.

Human Language Interfaces for Software Development

An application that aids in software development is CAUse. CAUse automatically generates use case diagrams from English requirement specifications [31]. The developers of this system defined and represented the semantic implications of certain linguistic markers. These later formed the basis of the rules used in the generation of the use case diagram.

A natural language database interface, Alladin, automatically generates the SQL statement from the English question and retrieves the answer from the database [22]. Alladin is also capable of anaphora and ellipsis resolution to support a simple dialogue system. A sample dialogue with Alladin is shown in Listing 1.

User: How many people live in Barangay 1?

Aladdin: 489

User: How about Barangay 2?

Alladin: 367

User: How many of them are male?

Alladin: 203

Listing 1. Sample dialogue with Alladin

Listing 2 illustrates a sample natural language query fed into Alladin and the corresponding system-generated SQL statement from the query.

User Input: How many people live in Barangay 1?

SQL statement generated by Alladin:

Select count (*) from MEMBERS where MEMBERS.brgy = 1

Listing 2. Sample SQL statement generated by Alladin

Virtual Museum

On the domain of culture and the arts, an on-line virtual museum VIGAN was developed [7]. The system generates artifact descriptions in natural language from structured internal representation of the information. This allows flexible generation of English descriptions, since the words used may vary and the descriptions generated may differ depending on the user's interest and preferences. From the structured information in the database as follows:

Original-painting-artist: Juan Luna, Filipino

Education: Bachilerato (1853, San Juan de Letran)

Award: Gold medal for painting "Spolarium"

Height: 4 meters

Width: 7 meters

The system will generate the following textual information together with the sample picture of the work: "The Spolarium is a painting by a Filipino artist, Juan Luna. The Spolarium measures four meters in height and seven meters in width." Since the user has indicated that he/she is not interested to know about his educational background, this information has been withheld from the user.

Dialogue Systems

HelloPol is a question-answering system that converses with the user in English within the political domain [3]. The system has been fed with political news articles, and information extraction has been integrated into the system to automatically extract relevant information from the articles into a more structured type of representation (or simply, a database) for use in the question-answering system. The user may ask factoid questions (who, what, when, where) and the program answers these by referring to the database of information. It is also an adaptive question-answering system in that it considers in its responses the user's topic preference during the course of the dialogue.

Sign Language Processing

Most of the work that we have done focused on textual information. Recently, we have explored on video formats for the inclusion of the Filipino sign language in our researches. Next in line will be the speech corpus.

As mentioned in a previous section, the Filipino sign language has been included in our attempt to come up with a corpus on Philippine languages. The signs and discourse are recorded in videos, which are edited, glossed and transcribed. Video editing merely cuts the video for final rendering, glossing allows association of sign to particular words, and transcription allows viewing of textual equivalents of the signed videos.

Work on the automatic recognition of Filipino sign language involves digital signal processing concepts. Initial work has been done on sign language number recognition [37] using color-coded gloves for feature extraction. The feature vectors were calculated based on the position of the dominant-hand's thumb. The system learned through a database of numbers from 1 to 1000, and tested by the automatic recognition of Filipino sign language numbers and conversion into text. Over-all accuracy of number recognition is 85%.

Another proposed work is the recognition of non-manual signals focusing on the various part of the face; in particular, initially, the mouth is to be considered. The automatic interpretation of the signs can be disambiguated using the interpretation of the non-manual signals.

Text to Speech Systems

PinoyTalk is an initial study on a Filipino-based text to speech system that automatically generates the speech from input text [5]. The input text is processed and parsed from words to syllables, from syllables to letters, and assigned prosodic properties for each one. Six rules for Filipino syllabication were identified and used in the system. A rule-based model for Filipino was developed and used as basis for the implementation of the system. The following were determined in the study considering the Filipino speaker: duration of each phoneme and silences, intonation, pitches of consonants and vowel, and pitches of words with the corresponding stress. The system generates an audio output and able to save the generated file using the mp3 or wav file format.

Pun Generator

A template-based pun extractor and generator have been developed that learns templates from training examples [27]. It utilizes both phonetic and semantic knowledge to capture the knowledge about puns and their generation. Word relationships, variables and tags are captured. From the test results, it has been shown that the system is capable of generating unique punning riddles from the learned templates. Evaluation also shows that the generated punning riddles are almost at par with human-made riddles.

Future Directions

Through the NLP laboratory of the College of Computer Studies, De la Salle University, varied NLP resources have been built, and applications and researches explored. Our faculty members and our students have provided the expertise in these challenging endeavors, with multi-disciplinary efforts and collaborations. Through our graduate programs, we have trained many of the faculty members of Universities from various parts of the country; thus, providing a network of NLP researchers throughout the archipelago. We have organized the National NLP Research Symposium for the past five years, through the efforts of the NLP laboratory of CCS-DLSU, and through the support of government agencies such as PCASTRD, DOST and CHED, and our industry partners. Last year, we hosted an international conference (the 22nd Pacific Asia Conference on Language, Information and Computation) which was held in Cebu City in partnership with UPVCC and Cebu Institute of Technology. We have made a commitment to nurture and strengthen NLP researches and collaboration in the country, and expand on our international linkages with key movers in both the Asian region and elsewhere. For the past five years, we have brought in and invited internationally-acclaimed NLP researchers into the country to support these endeavors. Recently, we have also received invitations as visiting scholars, and participants to events and meetings within the Asean region which provided scholarships, which in turn, we also share with our colleagues and researchers in other Philippine universities.

It is an understatement to say that much has to be explored in this area of research that interleaves diverse disciplines among technology-based areas (such as NLP, digital signal processing, multi-media applications, and machine learning) and other fields of study (such as language, history, psychology, and education), and cuts across different regions and countries, and even time frames. It is multi-modal and considers various forms of data from textual, audio, video and other forms of information. Thus, much is yet to be accomplished, and experts with diverse backgrounds in these various related fields will bring this area of research to a new and better dimension.

7. ACKNOWLEDGEMENTS

The authors would like to thank the other CCS-DLSU faculty members of the NLP laboratory namely Danniel Alcantara, Allan Borra, Ethel Ong and Solomon See who have all contributed to where we are now as a research laboratory, together with our undergraduate and graduate students who have worked with us in the laboratory's endeavors. We also acknowledge the support of our consistent Government partners, the Commission on Higher Education (CHED), CHED-Zonal Research Center (CHED-ZRC), the Philippine Council for Advanced Science and Technology Research and Development, Department of Science and Technology (PCASTRD/DOST), Komisyon sa Wikang Filipino (KWF), and the National Commission for Culture and the Arts (NCCA).

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