java - 如何让TuProlog识别无效事实？

Question

我有以下两个 Prolog 文件:

ontology.pl:

isSite(Url) :- string(Url).
guestPostPublished(GuestPostId, Date, Site, Url) :-
 string(GuestPostId),
 date(Date),
 isSite(Site),
 string(Url),
 \+(guestPostPublished(GuestPostId, _, _, _)).

invalidFile.pl:

isSite('somesite.com').
guestPostPublished(
    'gp1',
    date(2016,2,2),
    'somesite.com',
    'someUrl').

guestPostPublished(
    'gp1',
    date(2016,2,2),
    'somesite.com',
    'anotherUrl').

invalidFile.pl 无效，因为它违反了 ontology.pl 中指定的所有 GuestPostId 必须唯一的规则。

当我将该数据加载到引擎中时，我会抛出一些异常，表明数据无效。但事实并非如此。

我做错了什么？当我向 TuProlog 提供无效数据时，如何确保引擎，我收到某种通知(例如异常或某些标志)？

这是我的代码的相关片段(您可以找到整个代码 here ):

@Test
public void test2() throws InvalidObjectIdException, IOException,
        MalformedGoalException, InvalidTheoryException, UnknownVarException, NoSolutionException,
        NoMoreSolutionException, InvalidLibraryException {
    final Prolog engine = createEngine();

    try
    {
        loadPrologFiles(engine, new String[]{
                "src/main/resources/ontology.pl",
                "src/main/resources/invalidFile.pl"
        });
        Assert.fail("Engine swallows invalid Prolog file.");
    }
    catch (final Exception exception) {
        // TODO: Check that the right exception is thrown
    }
    final List<String> result = getResults(engine, "guestPostPublished(_,X,_,_).", "X");
    System.out.println("result: " + result);
}

private Prolog createEngine() throws InvalidObjectIdException {
    final Prolog engine = new Prolog();
    engine.addOutputListener(new OutputListener() {
        public void onOutput(OutputEvent outputEvent) {
            System.out.println(String.format("PROLOG: %s", outputEvent.getMsg()));
        }
    });
    Library lib = engine.getLibrary("alice.tuprolog.lib.OOLibrary");
    ((OOLibrary)lib).register(new Struct("stdout"), System.out);
    return engine;
}

private void loadPrologFiles(final Prolog engine, final String[] files) throws IOException, InvalidTheoryException {
    final List<String> paths = Arrays.asList(files);
    final StringBuilder theoryBuilder = new StringBuilder();

    for (final String path : paths) {
        theoryBuilder.append(System.lineSeparator());
        theoryBuilder.append("% ");
        theoryBuilder.append(path);
        theoryBuilder.append(" (START)");
        theoryBuilder.append(System.lineSeparator());
        theoryBuilder.append(FileUtils.readFileToString(new File(path)));
        theoryBuilder.append(System.lineSeparator());
        theoryBuilder.append("% ");
        theoryBuilder.append(path);
        theoryBuilder.append(" (END)");
        theoryBuilder.append(System.lineSeparator());
    }

    final Theory test1 = new Theory(theoryBuilder.toString());
    engine.setTheory(test1);
}

private List<String> getResults(final Prolog engine, final String query, final String varName) throws
        MalformedGoalException, NoSolutionException, UnknownVarException, NoMoreSolutionException {
    SolveInfo res2 = engine.solve(query);

    final List<String> result = new LinkedList<String>();
    if (res2.isSuccess()) {
        result.add(res2.getTerm(varName).toString());
        while (engine.hasOpenAlternatives()) {
            res2 = engine.solveNext();
            final Term x2 = res2.getTerm("X");
            result.add(x2.toString());
        }
    }
    return result;
}

Answer 1

要在 Prolog 事实表上设置数据完整性约束，您需要采用不同的方法。我建议您首先尝试在纯 Prolog 中执行此操作，而不使用 Java 位，只是为了了解正在发生的情况。

如果数据库是静态的并且不会更改，则很简单:只需加载它，然后对其运行查询以执行数据完整性检查。例如，您有一个包含单列的表 site/1，并且您希望确保所有值都是字符串:

There is no site(S) so that S is not a string

\+ ( site(S), \+ string(S) )

如果您想将其包装到谓词中，则必须使用与表不同的名称来命名谓词!

site_must_be_string :-
    \+ ( site(S), \+ string(S) ).

或者，对于另一个，一个唯一的列(主键):

There are no duplicates among the first arguments to guest_post_published/4

findall(ID, guest_post_published(ID, _, _, _), IDs),
length(IDs, Len),
sort(IDs, Sorted),   % sort/2 removes duplicates!
length(Sorted, Len). % length does not change after sorting

您可能还需要将其包装在它自己的谓词中。