Dr. Dobb's Journal - February 2008 - (Page 34)

D02gray_p5ma.qxp 12/7/07 2:25 PM Page 34 Core Technology BIBPORT: CREATING BIBLIOGRAPHIC REFERENCES continued from page 30 of the reference. This illustrates the need for the parser to understand the types of visual formatting cues that can be found in reference lists. The capability to distinguish visual cues requires at least rudimentary understanding of text formatting (underlining and italicization) of a wordprocessor’s file format. BibPort has a plug-in architecture that has a parser manager as a front-end to any number of citation formats Text Formatting Cues to Assist in Resolving Ambiguities Properly interpreting a reference requires nontextual cues offered by text formatting. To obtain nontextual properties, BibPort requires a mechanism for understanding the document’s underlying file format. A manuscript usually follows the standard format of the host wordprocessing tool, such as the structure of a Word document. BibPort understands the Word format and extracts the nontextual information in the citation. Mining a reference through visual cues is not easy. Many common formats, including the Word document format, encode information in a binary format rather than plaintext. Furthermore, mining the visual cues is tied to a specific wordprocessor’s output and is difficult to generalize due to differences in the file formats of wordprocessors. The situation has additional complexity because a parser may need to evolve with the host wordprocessor. For example, each new version of Word tends to change the standard document format in some way, requiring either a more complicated parser or several parsers to decode all formats. BibPort includes a format-agnostic parser that processes the tokens of a document without understanding the specific underlying format. BibPort’s own internal data structure can be extended with a wrapper to integrate with the host wordprocessor’s data structure to deliver tokens to the parser. Many wordprocessors provide an API to access the internal structure of documents. For example, Word allows such interaction through VSTO and the Word Object Model (WOM). Ambiguity Within Reference Types Ambiguity within a single grammar rule can be resolved partially through nontextual information, which can serve as a guide to delimit the beginning and ending of certain elements (a journal name) of a reference list entry. However, additional challenges remain when parsing a full set of reference types. The Typical Style Creating the BibPort grammar for a citation format is not difficult—the process is similar to defining the grammar for a simple programming language. However, there are several citation formats that fail to distinguish between similar types of publications. In the example BibPort grammar for APA (Figure 2), you can see that the grammar productions distinguish between a book and a magazine. At a visual level, the title of the book is completely underlined, but the article title is not. Such visual cues can serve as attributes to assist the parser for a specific grammar. Therefore, there is no ambiguity between a book and magazine in the APA grammar when nontextual information is available. However, note that the grammar for the journal simply references the grammar for the magazine. This is because the APA style does not distinguish between magazines and journals. However, other citation formats may decide to treat magazines and articles differently, and many management tools distinguish between magazine articles and journal articles. Therefore, even though the grammar may be ambiguous, it’s important that the parser have some mechanism for disambiguation so that integration between different styles is possible. In a grammar specification, optional information is specified by square brackets; for instance, the volume and issue information for the magazine in Figure 2. It is difficult to analyze a citation grammar to produce a parser that’s aware of all ambiguities. Userdirected parsing needs to disambiguate some citation formats. Most citation formats permit the description of several dozen types of references. In terms of selecting candidates for ambiguous references, BibPort streams every reference list entry to the parser for each reference type. This way, parsers can remain simple, yet all ambiguities are always detected with candidate suggestions. After an ambiguity is found, users must be involved. Of course, BibPort output should be reliable, so BibPort does not guess about the correct classification of an ambiguous reference without consulting users. Because BibPort is integrated with Microsoft Word, a pop-up dialog menu for each ambiguous reference list entry is displayed to users, who are asked to classify the reference from among the recommended candidates. A similar action can be taken for a reference for which the parser cannot find a suitable production match. An interface lets users populate a data structure with appropriate information, as well as indicate the reference type. BibPort in Action One of the new concepts used in Office 2007 is the “ribbon,” which replaces the old menu system from Office 2003. With ribbons, users interact with toolbar-like entities that allow switching to different contexts based on the task at hand. Because VSTO is designed to work with Office 2007, it lets programmers Figure 1: APA-style citation, with and without formatting. Figure 2: Subset of the APA grammar used in BibPort. 34 Dr. Dobb’s Journal l www.ddj.com l February 2008 http://www.ddj.com

Table of Contents Feed for the Digital Edition of Dr. Dobb's Journal - February 2008

Dr. Dobb's Journal - February 2008 Contents Hmmmm Alia Vox Developer Diaries Developer’s Notebook South American Software Development Conversations Inside Visual Studio 2008 BibPort: Creating Bibliographic References Continuous LINQ The ZK Framework Static Testing C++ Code The Agile Edge Effective Concurrency Swaine’s Flames

Dr. Dobb's Journal - February 2008

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