Zillabit Projects

Update - 2006

XML document object class

• Your document type is relatively simple and not changing in the future --- writing some code specific to your document type is required
• The size of your built code is critical, for example you are building downloadable client code (compare to full DOM XML parsers which are tens or hundreds of times larger)

The object oriented code consists of the parser class (expatParser.cpp and expatParser.h) and the interface (docObjectIface.h) for which you must implement a subclass specific to your document type. In the example below i've just put those three files into the expat directory with James Clark's code, but of course you could place these files elsewhere if you deal with include paths properly. Also, I recommend using preprocessor definition XML_MIN_SIZE (used by James Clark's code, not mine).

This code was originally written in 2000 and used successfully for two commercial implementations. One was in a downloadable Windows application, and the other was in an ActiveX control, but in both cases the convenience of a document object class and the small size of the compiled code were very advantageous, and the specific document types were simple enough that implementation using this code was easy enough.

Since this code was written, Tim Smith has done a similar project. There are probably some other ones out there too.

Example: Shakespeare plays dialog search

The task we'll demonstrate is this: parse all the plays, then allow a user to specify a string of dialog for which to search. This application will then find all instances of that string in a line of dialog, and let us know the play, act, scene, and speaker for each instance. For simplicity we'll just use the C strstr() function on each line as the lines were split up by the author. (i.e. we won't span lines).

Because we can ignore some features of the documents (e.g. we don't care about the Dramatis Personae information or the Scene Description) we have a pretty simple view of the documents:

<PLAY> [we expect only one PLAY per document] <TITLE>The Tragedy of Hamlet, Prince of Denmark</TITLE> [we only expect one TITLE tag per PLAY] <ACT> [we expect multiple ACTs per PLAY] <TITLE>ACT I</TITLE> [we expect only one TITLE tag per ACT] <SCENE> [we expect multiple SCENEs per ACT] <TITLE>SCENE I. Elsinore. A platform before the castle.</TITLE> [we expect only one TITLE tag per SCENE] <SPEECH> [we expect multiple SPEECHes per SCENE] <SPEAKER>BERNARDO</SPEAKER> [we expect only one SPEAKER per SPEECH] <LINE>Well, good night.</LINE> [we expect multiple LINEs per SPEECH] <LINE>If you do meet Horatio and Marcellus,</LINE> <LINE>The rivals of my watch, bid them make haste.</LINE> </SPEECH> [more SPEECHes here] </SCENE> [more SCENEs here] </ACT> [more ACTs here] </PLAY>

At any point, if we encounter any unrecognized tags we'll just ignore them. If we expected exactly one instance of a tag, but we encounter zero or more than one instance, we'll print a warning message (to the stream the user of the object requests, which could be NULL, stderr, or a file, for example) but will deal with the situation gracefully. (In fact, in the plays there are some SPEECHes with multiple SPEAKERs, but for our application noting only one of them is fine.)

The document class source code is shakespearedoc.cpp and shakespearedoc.h. The source code for the application itself is shakespearesearch.cpp. For convenience, you can download all this source code ready to be built in a MSVC project, xmlexample-MSVC.zip. If you'd just like to run it, here's a windows executable: shakespearesearch.exe. I haven't gotten around to doing a makefile for make/gcc environments but it should be quite easy to do and the code should be fully portable --- just be sure to note the XML_MIN_SIZE preprocessor flag as mentioned above.

Here's an example of running the application. Note that in this example we are using a shell that's capable of exanding wildcard filenames; if running under DOS you'd have to explicitly name all the XML files on the command line. On a 750 MHz Pentium it takes about 1 or 2 seconds to parse all the plays, and the time to do the searches is too fast to measure.

>shakespearesearch *.xml Parsing file : a_and_c.xml Parsing file : all_well.xml Parsing file : as_you.xml Parsing file : com_err.xml Parsing file : coriolan.xml Parsing file : cymbelin.xml Parsing file : dream.xml Parsing file : hamlet.xml Parsing file : hen_iv_1.xml Parsing file : hen_iv_2.xml Parsing file : hen_v.xml Parsing file : hen_vi_1.xml Parsing file : hen_vi_2.xml Parsing file : hen_vi_3.xml Parsing file : hen_viii.xml Parsing file : j_caesar.xml Parsing file : john.xml Parsing file : lear.xml Parsing file : lll.xml Parsing file : m_for_m.xml Parsing file : m_wives.xml Parsing file : macbeth.xml Parsing file : merchant.xml Parsing file : much_ado.xml Parsing file : othello.xml Parsing file : pericles.xml Parsing file : r_and_j.xml Parsing file : rich_ii.xml Parsing file : rich_iii.xml Parsing file : t_night.xml Parsing file : taming.xml Parsing file : tempest.xml Parsing file : timon.xml Parsing file : titus.xml Parsing file : troilus.xml Parsing file : two_gent.xml Parsing file : win_tale.xml Enter a search string, or RETURN to quit searching: to kiss you FOUND OCCURANCE number 1: PLAY 14: The Third Part of Henry the Sixth ACT 3: ACT III SCENE 3: SCENE III. France. KING LEWIS XI's palace. SPEECH 17: WARWICK LINE 3: Humbly to kiss your hand, and with my tongue FOUND OCCURANCE number 2: PLAY 15: The Famous History of the Life of Henry the Eighth ACT 1: ACT I SCENE 4: SCENE IV. A Hall in York Place. SPEECH 42: KING HENRY VIII LINE 3: And not to kiss you. A health, gentlemen! FOUND OCCURANCE number 3: PLAY 28: The Tragedy of King Richard the Second ACT 1: ACT I SCENE 3: SCENE III. The lists at Coventry. SPEECH 13: Lord Marshal LINE 2: And craves to kiss your hand and take his leave. Enter a search string, or RETURN to quit searching: doughnut Enter a search string, or RETURN to quit searching: on the stream FOUND OCCURANCE number 1: PLAY 1: The Tragedy of Antony and Cleopatra ACT 1: ACT I SCENE 4: SCENE IV. Rome. OCTAVIUS CAESAR's house. SPEECH 6: OCTAVIUS CAESAR LINE 6: Like to a vagabond flag upon the stream, FOUND OCCURANCE number 2: PLAY 23: The Merchant of Venice ACT 1: ACT I SCENE 1: SCENE I. Venice. A street. SPEECH 4: SALARINO LINE 12: Would scatter all her spices on the stream, FOUND OCCURANCE number 3: PLAY 35: The History of Troilus and Cressida ACT 2: ACT II SCENE 3: SCENE III. The Grecian camp. Before Achilles' tent. SPEECH 57: ULYSSES LINE 2: But carries on the stream of his dispose Enter a search string, or RETURN to quit searching: (RETURN)

License

License for James Clark's expat is explained on his site.