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Exercise 1

(10 points)

The goal in this year's exercise is to develop an XML-based format to represent data for an auction house (like eBay). In Exercise 1 you will create an XML Schema and XML document and in Exercise 2 you will be querying and transforming this document with XML-related technologies.

An auction house offers products. A user can place a bid on a specific product. After a set date, the auction for a product ends. The user with the highest bid wins the product.

Remark: The following data format can be seen as a database for an auction house.

In this exercise we will develop the XML Schema and an XML Document, that validates against the XML Schema. Afterwards, we will translate this XML Schema into a Document Type Definition (DTD).

XML Schema auctions.xsd

The first part of this exercise consists of writing an XML Schema document auctions.xsd. The XML Schema should allow for XML Documents according to the following definitions:

Element auctions

The root element auctions stores all the relevant information for the auction house.

It contains the following 3 child elements in exactly this order, but each element is optional:

Element products

The element products has no attributes and is a child element of auctions. The subtree rooted at products stores the products. It may contain an unbounded number of product elements.

Element product (child of products)

The element product stores a product. It contains in this order:

  1. exactly one name element, which stores the name of the product as string,
  2. an optional description element, describing the product,
  3. an optional expired element, which is empty; and
  4. zero or an unbounded number of category elements.
The product element has two attributes:

Element description

The element description is used to give a product description. It can contain elements it and a, and additionally, also text (in any order, with any multiplicity). The element a contains just text and has an attribute href, which contains a link to some other page. The element it contains text.

For example

<description>This is an <a href="example.htm">example</a> <it>text </it>!</description>

is a valid description element.

Element category

The element category assigns a category to a product. The value of the element is either "book", "movie" or "music".

Element users

The element users has no attributes and is a child element of auctions. The subtree rooted at users saves the users. It may contain an unbounded number of user elements.

Element user

The element user describes a possible user of the auction house. It has the attribute username, which should be unique and identifies the user. Additionally, it has an attribute password storing the password of the user. The element user has the following child elements in exactly this order:

    • Either the element fullname that contains a string, or
    • the element name which contains the elements firstname and lastname (both contain a string).
  2. An unbounded number of email elements, all of which contain a string.
  3. The element balance that contains a nonnegative integer.

Element bids

The element bids has no attributes, but may contain an unbounded number of product elements. These product elements are of different type as the child element product of products. This type is described next.

Element product (child of bids)

The element product describes the bids for this product. It has an attribute id which is a nonnegative integer and refers to the id of a product element in products. Each product may only have one product element as child of bids. It has one or an unbounded number of bid elements.

Element bid

The bid element stores a nonnegative integer, which represents the bid of a specific user. Its only attribute user references a username attribute of a user element.

Keys

Add the following keys to your document:

  • userKeys for the usernames.
  • productKeys for the products (child of products).
The keys are referenced in the following fields:
  • userKeys is referenced in the user attribute of the bid element.
  • productKeys is referenced in the id attribute of the product element (child of bids).

General Remarks

Please pay attention to the following remarks:

  • If nothing else is mentioned all elements and attributes are required. The word "may" hints you to optional elements or attributes.
  • All numbers are integers.

Summary

  • Files: auctions.xsd
  • Maximum number of points: 5

XML Document auctions-xsd.xml

Create an XML Document auctions-xsd.xml for the XML Schema auctions.xsd. The XML Document should satisfy the following criteria:

  • Create at least three product elements (child of products).
  • Create three users.
  • Create for each product at least one bid element.
  • Create at least six bids.

Make sure that your XML Document auctions-xsd.xml validates against your XML Schema auctions.xsd. This can be done with the following command (after you have installed xmllint:

xmllint --schema auctions.xsd auctions-xsd.xml

Downloads and user instructions to xmllint can be found on our exercise page.

Summary

Document Type Definition (DTD) auctions.dtd

Create a Document Type Definition (DTD) auctions.dtd, based on the above description. If some specification has a very complicated or no equivalent at all in DTDs, then make reasonable assumptions. If it is not possible that your XML document from above validates against your DTD, then create a new XML document auctions-dtd.xml, with the same information as in auctions-xsd.xml, that validates against your DTD.

Be prepared to explain in the assignment discussion which functionalities are not possible with DTDs. But, you don't need to create large number ranges as enumerations (e.g. "Numbers between 1 and 72 as an enumeration of 72 numbers).

Remarks

Make sure that at least the XML Document auctions-dtd.xml validates against your DTD auctions.dtd. This can be done with the following command (after you have installed xmllint:

xmllint --dtdvalid auctions.dtd auctions-dtd.xml

Summary

Submission

In total you have to upload the following files:

These files should be zipped and the resulting ZIP-file exercise1.zip has to be uploaded until 05.05.2015 23:59 in TUWEL. We will grade the last uploaded solution.

Assignment discussion

You can receive at most 10 points for Exercise 1. During the assignment discussion we will not only check your solution for correctness, but will also ask some questions regarding the used technologies. Please be prepared to answer the questions mentioned in this document as well.

To obtain the full number of points your solution has to be solved correctly and you have to be able to explain it. Copied solutions are awarded 0 points!

In your own interest come ontime to your assignment discussion or else we don't guarantee that your solution is completely checked in the remaining time of the reserved slot.

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