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<Paper uid="W99-0804">
  <Title>I Intranet learning tools for NLP</Title>
  <Section position="2" start_page="0" end_page="0" type="metho">
    <SectionTitle>
1 Learning Objectives
</SectionTitle>
    <Paragraph position="0"> Behind the practical work reported in the rest of this paper is an assumption that introductory CL education should provide learning environments both for the linguistic and computational aspects of CL.</Paragraph>
    <Paragraph position="1"> For the former aspect, a simplified grammar development environment is required; for the latter, an interactive exploratory tool which can step through processes like constructing a derivation, applying a specific search algorithm, relating the data structures to the representations produced as the result of analysis.</Paragraph>
    <Paragraph position="2"> ,~ The Pa,ser - Netseape I~1~\] E _File _Edit View Go Communicator Help ~i Back Forv,,~rd Reload.. Home Seamh Netscape P,int Seeuhl.~ Stop~ I &amp;quot;~! v . |' . . , T .:::l ' .J ,, ,,,,,,- ........ &amp;quot; , ,, - , ,i; .... ii\];;;,i~,~ ~ Bookma,ks ...~ Locaton&amp;quot; st ac uk/webparser/cl,entl 0/chent html ~ ~ 'V,/ha\[sRelated Type string to be parsed - no punctuation: IAn airline took american hotel chain over an J</Paragraph>
    <Paragraph position="4"/>
  </Section>
  <Section position="3" start_page="0" end_page="0" type="metho">
    <SectionTitle>
2 Tools for exploring grammars and
</SectionTitle>
    <Paragraph position="0"> linguistic representations In the preceding paragraph, we contended that simplified grammar development environments are required. Why not the real thing, like the Alvey Tools, Geppetto, LFG workbench, Pleuk, ProFit, ALEP et al? The target audience is the introductory CL student, either in the first year of a study programme or taking a CL module as part of a cognate discipline. Tools used by researchers are for later in the course, if we manage to retain the interest of the students, which we will only do if we make CL tools as accessible as the generality of IT applications. Graphical user interfaces are essential: to give a student a graphics workstation and have them interact with Prolog in a terminal window conveys an unfavourable impression.</Paragraph>
    <Paragraph position="1"> Some excellent learning software for CL is available, such as the Linguistic Instruments tools for CFGs DCGs, PATR and categorial grammars. Their main drawback is that they are tied to the MacOS platform.</Paragraph>
    <Section position="1" start_page="0" end_page="0" type="sub_section">
      <SectionTitle>
2.1 Software platforms for portability
</SectionTitle>
      <Paragraph position="0"> There are implementations of the programming languages considered suitable for NLP that hava graphical user interface (GUI) development tools, but unfortunately these are not standard.</Paragraph>
      <Paragraph position="1"> The ideal would be to use programming languages and GUI development tools that are available on different computer systems. The two most widely known platform-independent GUI development tools are Tcl/TK and Java.. Of the two, Tcl/TK is simpler, but Java has the crucial advantage that it can 'run anywhere' in a web browser, whereas for Tcl/TK, the user has to obtain a plug-in.</Paragraph>
      <Paragraph position="2"> Integrating tools with teaching material Another use of Java running in a browser is to embed the interactive elements into hypertext, allowing a close linkage of textual learning materials with practical activities. As well as using Java to provide run-anywhere programs, teaching materials can be enhanced by applets which display linguistic analyses graphically, and even have the displayed information open to manipulation.</Paragraph>
      <Paragraph position="3"> The grammat)cal resources used are the grammars in PATR-II as presented in Gazdar and Mellish, 1989.</Paragraph>
      <Paragraph position="4"> The client-side itree and AVM-drawing programs illustrated in Figure 1 can be used independently of the server discussed below, to produce animated teaching notes. The data to be displayed and manipulated in this applet is specified in applet's parameters, so it is possible to use it to illustrate different analyses at different parts of an educational hypertext. There is one structured string parameter which encodes the tree, and one further parameter for each node, which encodes the content of the respective AVMs.</Paragraph>
      <Paragraph position="5"> The Thistle tree-editing suite (Calder, 1998) is a well-developed interactive tool for working with linguistic representations such as trees and AVMs is a more sophisticated alternative.</Paragraph>
      <Paragraph position="6"> However, the tree-drawing program described is only a part of a more sophisticated mechanism which links the linguistic information displays to on-line parsing,</Paragraph>
    </Section>
  </Section>
  <Section position="4" start_page="0" end_page="0" type="metho">
    <SectionTitle>
3 On-line Parsing
</SectionTitle>
    <Paragraph position="0"> Having chosen to use Java for the development of graphical displays of linguistic data, we have to consider what is the most appropriate engine for the analysis or generation behind them. One possibility would be to re-write the code for those algorithms in Java, but this ignores the possibility of re-using existing programs written in Prolog or LISP, which are documented in various textbooks. These implementations are more established than existing Java-based parsers, which have not so far featured in published learning materials.</Paragraph>
    <Paragraph position="1"> There are several practical ways in which a Prolog or LISP parser can have its output displayed graphically in a browser. One is to invoke the parser from within a CGI script on a web server. This strategy has been adopted by Ramsay (1999) for presenting the Parasite project on the WWW.</Paragraph>
    <Paragraph position="2"> A disadvantage is that each request involves the overhead of starting a new Prolog process, and a consequently inflated response time, as well as complex arrangements to maintain dialogue state information.</Paragraph>
    <Paragraph position="3"> Client-server parsing In the CCL webparser system, the LISP-based parsing program acts as a server which accepts socket connections from the Java applet that handles the display.</Paragraph>
    <Paragraph position="4"> The intention was that the LISP parser should be a black box, so we elected to build th server using Expect. This is an extension of Tcl/TK (Libes, 1995) that is specially designed to 'automate' interactive programs.</Paragraph>
    <Paragraph position="5"> The Expect program spawns a LISP process and then controls it by simulating the user with its send and expect commands. It uses its send command to load linguistic resources, and then it opens a server socket, awaiting requests from networked clients.</Paragraph>
    <Paragraph position="6"> When socket connections are accepted from users' browser clients, the expect program passes these on to the LISP parser program, and awaits the response, which it passes back to the client.</Paragraph>
    <Paragraph position="7"> The advantage of using Expect as an intermediate layer is that it enables the LISP process to react to different client programs without having to restart to serve each of them. It also lets the server save the results of a parse, e.g. a chart, and let the user ask for information that is stored in chart edges for some time after the initial parse was done. When a parse request is processed, a reference number is generated and the chart is cached, indexed by that number. The reference numbers are notified to the client as part of the message summafising the result of the analysis.</Paragraph>
    <Paragraph position="8"> The client-server protocol A simple protocol has been defined for communication between the client and the server, as shown in Table 1. The client prefixes each request by one of the keywords parse, tree, and avm.</Paragraph>
    <Paragraph position="9"> Table 1 Client-server protocol for web parser  p# reference number of the parse request tree# nth analysis produced in parse p# edge# nth edge from the chart of parse p# treenode is a triple node#, parent, label dagnode is a number dagedge is a triple fi'om, to, label Figure 1 illustrates this client-server system running in a Netscape browser.</Paragraph>
    <Paragraph position="10"> Educational use of the client-server parser The version displayed is under development, and still lacks some features it would need to be really useful in an educational context. The most important practical requirement is for the user to be able to modify the grammars and lexicons that the system uses. To make the program useful for reinforcing different stages in a course, the user has to be able to select alternative grammars, and to be able to edit his/her own. This is inconvenient to implement when the interface is an applet, because an applet is not normally permitted to save programs on the local machine. However, we expect to have a workaround for this in place for the next academic year.</Paragraph>
    <Paragraph position="11"> Being able to display the results of parsing in the form of conventional diagrams is an advance on textual interaction. When the student is working on a grammar, the displays produced give feedback which is much more readily understood than textual output.</Paragraph>
    <Paragraph position="12"> Students in the later years of the CL course have been able to use the system to visualise the results of parsing with grammars under development in another window. The planned file-management facilities will enable the program to be used regularly with the target users (students new to CL) in the next academic year.</Paragraph>
    <Paragraph position="13"> Tools to support the understanding of CL processing Understanding grammar notation is only part of what a CL student needs to learn in practical classes. Accordingly, we have started to develop a suite of tools that animate parsing algorithms using Java only, without the need for a server. The first of these was developed in a day, and lets the student step through the construction of a derivation, either top-down or bottom-up. This program is illustrated in Figure 2. It has been extended so users can supply their own rules. This program has been successfully deployed with first-year students already and appears to have enhanced their understanding of these basic concepts of formal language theory and parsing algorithms. The same program can be used, with different data, to illustrate search algorithms in general.</Paragraph>
    <Paragraph position="15"> To actavate, Chck m the Start state box after &lt;s&gt; and press the return key. Then choose rutes from the &amp;quot;Productions&amp;quot; list. For additi0nal help, click here. j  We are modifying this program so that it can show the agenda at each step of an automatic derivation to enhance the student's understanding of search algorithms in general.</Paragraph>
    <Paragraph position="16"> At some point, this program will be integrated with the graphical presentation elements.</Paragraph>
    <Paragraph position="17">  The software described in this paper is still under development. It has been used by students, but not yet extensively. It will be difficult to get objective information on what difference such accessible interactive learning tools make to the students' learning, but a study of usability will be conducted during the next academic session.</Paragraph>
    <Paragraph position="18"> The main advantage (for the teacher) in using a WWW-based environment for delivering natural language processing practical work to students is that once developed, the laboratory needs less specialist provision and staffing than before.</Paragraph>
    <Paragraph position="19"> Students can also work in their own time in campus-wide computer facilities without having to have NLP software installed.</Paragraph>
    <Paragraph position="20"> Planned developments The software described is at a rather immature phase of deyelopment, but most of the hard work has been done. Planned future developments after the file management facilities are completed include: * graphical viewers for the chart in chart parsing * dependency tree viewers * discourse representation viewers incremental tracing of generation algorithms Also on the agenda is to make on-line access to a range of well-known NLP programs an integral feature of all the teaching materials for introductory NLP. Using the same Expect-based meachnism, we can put user interfaces around taggers, morphological analysers, dictionaries and corpus-analysis programs and link to them all with hypertext.</Paragraph>
    <Paragraph position="21"> Conclusion We have described recent work on the implementation of student-oriented tools for natural language processing.</Paragraph>
    <Paragraph position="22"> Three kinds of tool have been developed, which complement those available elsewhere. Firstly a parameterisable applet which enables the lecturer to incorporate syntax trees with embedded attribute-value matrices into hypertext teaching materials. Second, a portable HTML-Java interface to a parsing server residing on a departmental intranet server.</Paragraph>
    <Paragraph position="23"> Finally, we have developed a tool that lets the student explore the process of analysis step-bystep, to reinforce understanding of the basic algorithms for NLP.</Paragraph>
    <Paragraph position="24"> Both the second and the third tool are now being enhanced to enable them to be used by students to develop their own resources, and effort is also under way to complete graphical viewers for a more complete inventory of linguistic representations.</Paragraph>
    <Paragraph position="25"> The client-server method of constructing an on-line parser with a user interface is an attractive approach because it allows us to re-use existing tools, for example those which are featured in teaching materials, such as Gazdar and Mellish (1989). The Expect plus Java technology provides a good solution for developing user interfaces for local use; the possibility of deploying these within hypermedia provides an additional opportunity to package the practical work within course materials.</Paragraph>
    <Paragraph position="26"> Tools used The client-server program was developed using JDK1.1.7, Allegro Common Lisp TM, version 5.0, Expect version 1.5, and the Apache Web server, under Solaris TM 2.6. The client programs have been tested on Netscape 4.0 and 4.5, and on Internet Explorer TM 4.0. It is planned to verify that the LISP portion can run under a freely available LISP, with a view to making the tools available to anyone interested in using them. Availability The client-server parser can be tried out at http://bermuda.ccl.umist.ac.uk/webparser/client ! 0/client.html When the software is available for download it will be announced at http://www.ccl.umist.ac.uk.</Paragraph>
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