You run a shop that sells magazines. You store information about your inventory in a relational database with the following schema:

-- Holds information on available magazines
CREATE TABLE MAGAZINE (
    ISBN VARCHAR(8) NOT NULL,
    ISSUE INTEGER NOT NULL,
    NAME VARCHAR(255),
    PUBLISHER_NAME VARCHAR(255)
    PRICE FLOAT NOT NULL,
    PRIMARY KEY (ISBN, ISSUE)
    FOREIGN KEY (PUBLISHER_NAME) REFERENCES PUBLISHER (NAME)
);

-- Holds information on magazine articles
CREATE TABLE ARTICLE (
    TITLE VARCHAR(255) NOT NULL,
    AUTHOR_NAME VARCHAR(128),
    PRIMARY KEY (TITLE)
);

-- Holds all the subtitles of an article
CREATE TABLE ARTICLE_SUBTITLES (
    ARTICLE_TITLE VARCHAR(255),
    SUBTITLE VARCHAR(128),
    FOREIGN KEY (ARTICLE_TITLE) REFERENCES ARTICLE (TITLE)
);

-- Join table linking magazines and articles
CREATE TABLE MAGAZINE_ARTICLES (
    MAGAZINE_ISBN VARCHAR(8),
    MAGAZINE_ISSUE INTEGER,
    ARTICLE_TITLE VARCHAR(255),
    FOREIGN KEY (MAGAZINE_ISBN, MAGAZINE_ISSUE) REFERENCES MAGAZINE (ISBN, ISSUE),
    FOREIGN KEY (ARTICLE_TITLE) REFERENCES ARTICLE (TITLE)
);

-- Each magazine has a 1-1 relation to its publisher
CREATE TABLE PUBLISHER (
    NAME VARCHAR(255) NOT NULL,
    REVENUE FLOAT NOT NULL,
    PRIMARY KEY (NAME)
);

You've decided to write an application that will let you query your database through JDO.