BCS HIGHER EDUCATION QUALIFICATIONS BCS Level 6 Professional Graduate Diploma in IT April 2010 EXAMINERS’ REPORT

WEB ENGINEERING
Examiners’ General Comments The pass rate this year has significantly increased from previous years, but despite this overall increase it is clear that there are a number of candidates who are ill-prepared for the examination. Candidates should particularly note that the paper aims to cover contemporary topics, and should keep abreast of current and popular developments in preparation for this paper. The examiners would repeat the general comments made before in their report: “The subjects covered currently include XML, web programming, web 2.0 and other current technologies. The paper attempts to be contemporary in the topics it covers, and each year will introduce some new topics within the remit of the published syllabus. It is important for candidates to know that whilst on occasion questions may look similar to those in past papers, the context and approach is often significantly different, which means that previous answers cannot simply be restated; thus it is not appropriate to memorise and re-state past paper answers. Additionally, the answer pointers provided here give guidance and are only a guideline and should not be merely quoted by candidates, but applied to the topic of the question.”

A1 a) i) Explain the role and structure of a DTD in relation to an xml document. ii) Explain the role and structure of an XML schema in relation to an xml document. iii) Explain how an xml document would call:  an internal DTD  an external DTD and;  an XML schema. b) i) Compare and contrast the workings of a DTD and an xml schema. You should state the benefits of using each. [3 marks] ii) Generate an appropriate sample XML document based on the xml schema in figure 1.1 [2 marks] [2 marks]

[3 marks]

[2 marks]

Figure 1.1 – XML Schema for Question A1 b) ii)

c)

Write an external DTD for the XML file in fig 1.2:  The element trainlog may contain, in any order, one or more session and progress_report elements.  A session element must first contain a duration element, followed by distance element, followed by a location element, followed optionally by a comment element, followed by zero or more photo elements.  The date and heartrate attributes in session are optional.  The type attribute in session must be present but allow only 3 values – running, swimming, cycling - with default set to running.  A photo element must contain a url attribute, but may not contain any text.  A progress_report element must contain one or more comment elements. [13 marks]

 50 5.5 Hyde Park Mid-morning run, a little winded throughout. 1.5 26.4 Crystal Palace Hilly ride, felt strong as an ox. 2.5 16.8 Regents Park Afternoon run, felt reasonably strong. Performance improved significantly

Figure 1.2 – Sample Document for Question A1 c)

Answer Pointers a) i) The purpose of a DTD (Document Type Definition) is to define the legal building blocks of an XML document. A DTD defines the document structure with a list of legal elements and attributes. ii) XML Schema is an XML-based alternative to DTD. An XML schema describes the structure of an XML document. The XML Schema language is also referred to as XML Schema Definition (XSD). iii) The DTD is declared in a DOCTYPE declaration beneath the XML declaration contained within an XML document:  Inline Definition:



External Definition:



XML schema:

b) i) DTD's are not namespace aware.

DTD's have #define, #include, and #ifdef – or, less C-oriented, the ability to define shorthand abbreviations, external content, and some conditional parsing. A DTD describes the entire XML document (even if it leaves "holes"); a schema can define portions. XSD has a type system. XSD has a much richer language for describing what element or attribute content "looks like." This is related to the type system. You can put a DTD inline into an XML document; you cannot do this with XSD. You have far more control over what is considered a valid XML document using a schema. You can even    ii) John Smith Jane Doe 24 Bond Street London W5 UK Empire Burlesque Special Edition 1 10.90 Hide your heart 1 9.90

extend your types from other types you've created, require uniqueness within scope, and provide lookups.

c) ]>

Examiners’ Guidance Notes Most candidates answered part (a) satisfactorily with some exceptions. Some students did not know about XML schema. There were some excellent answers to the comparison of DTD and xml schema, however, b(ii) was not done well. Some students did not create the required sample to demonstrate the use of an XML schema. Answers to part (c) were of good quality. Most candidates demonstrated good competence in writing DTDs, with minor errors in the finer details of attribute types and default values.

A2 a) A simple DTD to record company information is provided in figure 3.1. i) Explain what it means for an XML document to be “well formed” and “valid.” [1 mark]

ii) The XML document in figure 3.2 contains precisely four errors when validated against the DTD of figure 3.1. Identify all the errors and for each one provide a correction. Note: the line numbers are for your benefit and are not part of the XML code. [4 marks]
1. 2. 3. 4. 5. 6. 7.

Figure 3.1 – DTD for Question A3 a) and A3 c) Figure 3.2 – XML document with errors for Question A3 a) ii)
1. 2. 3. 4. 5. 6. 7. 8. 9. IBM

b) Data can be stored in child elements or in attributes as demonstrated by figure 3.3. Briefly state five factors to be considered when using attributes instead of child elements. [5 marks] Tove Jani Reminder Don't forget me this weekend! 12/11/2002 Tove Jani Reminder Don't forget me this weekend! 12 11 2002 Tove Jani Reminder Don't forget me this weekend!

Figure 3.3 – Example of child elements and attributes for Question A3 b)

c)

A simple DTD to record company information is provided in figure 3.1. The employment agency has updated the above simple DTD to record information on all client companies that have commissioned recruitment activity since the beginning of the year. Sample XML is shown in figure 3.4. There is now a need to render this information as a web page that can be accessed by the agency staff. Using the HTML template provided in figure 3.5, complete the missing code in figure 3.5 (the section marked ) to accomplish this. A mock-up of the required rendered page is shown in figure 3.6. [15 marks] IBM Bob Jones 0044112233 bjones@ibm.com Analyst Design payment systems London £30000 25 Feb 2010 Usability Engineer Evaluation of new systems Glasgow £28000 12 Mar 2010 ORACLE Bill Smart 0044454545 bsmart@oracle.com Database Designer OO background London £40000 25 Mar 2010

Figure 3.4 – Sample XML document for Question A3 c)

 Current Job Vacancies Current Job Vacancies Company Contact email Phone

Figure 3.5 – XSL stylesheet for Question A3 c)

Figure 3.6 – Mock-up of required web page for Question A3 c)

Answer Pointers a) i)  A well-formed document conforms to all XML syntax rules (e.g. opening tags must all have a closing tag, be nested properly etc.).



A valid document is a well-formed XML document that conforms to semantic rules (as defined in a DTD or XML schema)

ii) Errors are:    Line 5: invalid attribute value (the value for CODE needs quote mar Line 6: Undefined element type (company_name should be Company_name) Line 7: invalid start-tag (Required attribute not specified: page)

 Line 9: mismatched end-tag ( should be ) b) Some of the problems with attributes are:         c) DTD (not required)

attributes cannot contain multiple values (child elements can) attributes are not easily expandable (for future changes) attributes cannot describe structures (child elements can) attributes are more difficult to manipulate by program code attribute values are not easy to test against a DTD using attributes as containers for data, leads to documents that are difficult to read and maintain. use elements to describe data. Use attributes only to provide information that is not relevant to the data.,

XSLT (required) Current Job Vaccancies Current Job Vaccancies Company Contact Email Phone

 Job Title Salary Location Start Date

Examiners’ Guidance Notes Most candidates did very well on part (a), identifying the errors accurately in the XML document. Answers to part (b) varied from some very good answers to very weak ones. Students could have referenced the example given to articulate the factors to be considered when deciding to use child elements or attributes. Answers to part (c) varied from very good to very poor. Some candidates had no knowledge of how to render an xml document as a web page, HTML code was submitted to mirror the sample display which clearly was not right. Some candidates failed to realise that there were two nested for loops rather than two independent for loops as part of the xslt code. A new development seen for the first time regarding this topic was an emergence of a group of candidates who were ill prepared for this question with very low scores.

B3 You are acting as a consultant for a financial institution, advising on the development of an online banking service. a) One possible security risk when accessing a banking website from a publicly accessible computer, is a hardware key logger that captures passwords; this is often solved by using on-screen (virtual) keyboards to enter data into a web form. i) What is meant by the term “hardware key logger”? [2 marks] ii) Aside from the use of key loggers, outline four other security risks and, for each risk, detail a method to prevent it. [8 marks] b) The in-house developers have outlined three possible schemes for authenticating their users. You have been asked to comment on these systems both from a security perspective (how safe the scheme will be) as well as from a user’s perspective (how easy the scheme will be to use).

Proposed scheme A    Type in your email address Type in your password (6 characters, alphabetic) Select the first and the second digits of your PIN (6 digits) from a drop-down list

Proposed scheme B    System-generated user number (created on registration, 11 digits long) Type in your password (6-12 alphanumeric characters) Type in your favourite colour

Proposed scheme C       i) Type in your first name Type in your last name Type in your postcode/Zip code Type in your date of birth Type in your mother’s maiden name Enter a one-time code using a hardware bank card reader and your debit card.

Outline TWO strengths and TWO weaknesses of each of the three schemes.

[9 marks] ii) Devise a new scheme for authenticating users on this site which is superior to all three schemes [6 marks] outlined above. Explain how it overcomes the weaknesses identified in part b) i).

Answer Pointers a) i) A hardware keylogger is a device placed inbetween a computer and keyboard that captures all keyboard activity to an internal memory. ii) Sample risks include:  Brute forcing (locking out accounts after a small number of failures)  Phishing (Microsoft’s anti-phishing filter).  Packet sniffing (use encryption).  Keylogger on client machine (check physical hardware and/or run a rootkit checker/antivirus).  SQL injection attack (ensure all user inputs are validated on the server side).  Denial of service attack (maintain mirror of server application & data).  Spyware on client machine (use antivirus/spyware checkers).  Not destroying letters with sensitive information e.g. passwords (shred confidential documents when disposing). b) i) Possible answers: Strengths Weaknesses A  Reasonably easy to remember login  Short alphabetic password gives only details. ~300 million combinations => brute forcible.  Defends against keylogging by using drop down lists  Requiring only the first and second digit of the PIN gives only 100 combinations.  Partial defence against phishing by only needing two digits from the PIN. B  Reasonably strong password.  Difficult to remember login details (randomly generate user ID), so more  Relatively fast to log in (only three text likely to write details down. fields to be entered).  All data is typed, so susceptible to keylogging.

 Favourite colour might be guessable (e.g. most people would choose a primary colour or black) C  Susceptible to identity fraud, as login details are almost entirely based on common personal details.  Lots of details to be typed in.  Mother’s maiden name is known by other people (e.g. family members).  Hardware device is not likely to be convenient for people to carry around, limiting ease of use of service when mobile. ii) An open question, but solutions must address all weaknesses of the previous schemes (both security and usability), whilst remaining reasonably simple for the end user. Possibilities might include:     Selecting random digits from a 6 digit PIN instead of merely two predetermined ones. Asking for one personal detail from a random selection (e.g. mother’s maiden name, favourite colour, name of first pet). Offering to remember the system username (not advised for multi-user PCs or accessing the site from a public computer). Allowing passwords to be alphanumeric and of variable length, with a sensible minimum length (e.g. 6 characters).  Very easy to remember login details.  Requires a collection of details that would be very difficult to brute force (but not find out through other means).  Hardware device means that attackers need physical access to an item before they can attack.

Examiners’ Guidance Notes Part a) i) was mostly well answered, though many candidates described keyloggers in general and did not notice that the question referred to hardware keyloggers. Part a) ii) was typically well answered, although a number of candidates seemed to consider “viruses,” “worms,” and “trojans” to be three entirely distinct security risks when they are all aspects of the larger security threat of “malware.” Some candidates were too vague in the risks identified, with answers such as “hacking” – an answer as vague as this does not gain any marks. Finally, some candidates were simply giving the name of a security risk – the question specifically asks the candidate to outline the risk, i.e. briefly describe. Part b) was reasonably answered by most, though there was often an emphasis on the security aspects at the expense of the usability aspects (a requirement of the question). The generic (and meaningless) phrase “for security reasons” was provided as an answer in some cases – this style of answer does not attract any marks. Part c) was typically poorly answered, with many candidates simply using one feature from each of the given schemes. Some candidates went over the top with security, producing almost entirely unusable (and therefore not very useful) systems. Some candidates mentioned the “CAPTCHA” system without explaining how this would increase security, and without identifying the impact this may have on usability.

B4 a) Write HTML to construct the form as indicated in figure 4.1. When the button marked “Search for games” is pressed, the form should submit to a script called games.php [4 marks]

b) When invalid data is entered into a form, a well-designed system will spot the invalid data and report them back to the user with an error message. i) Why is it important to catch invalid data? [2 marks] ii) What would be an appropriate error message for a login attempt that fails due to an incorrect password (but correct username)? [2 marks]

c)

Better systems will automatically re-generate the form with most data already completed (to save the user from entering it a second time). i) With a justification, give one example of form data that should NOT be automatically completed in a regenerated form. [2 marks] ii) Write code (at the server side in ASP, PHP, or Perl) to validate that the date of birth entered is not in the future, and if there is an error re-generate the original form from part a) with the entered data already filled in. [5 marks] Notes:   You do not require regular expressions to complete this task, but you may use them if you wish. You may find the PHP function int strtotime (string $time) useful in this task (which parses a string into a Unix timestamp), where $time is a textual description of a date/time e.g. "2009-12-31" for the 31st December, 2009 or "now" for the current system time on execution.

d) The server has a database named Games, with a single table named GameRatings (as shown in figure 4.2). You may assume the web server and the database server are hosted on the same computer. This database holds details of age ratings for video games which are listed in figure 4.3. For parts ii) and iii), assume that the php script games.php has already established a valid connection to this database. In all cases, you should state the language you are using (ASP, PHP or Perl). i) Write code to connect to the database. [1 mark] ii) Write code to retrieve the details of the game with the title that is exactly the same as the text entered in the “Enter the game title” field. [3 marks] iii) Write code to retrieve and display (in an appropriate format) the details of all games that can be bought by the person whose date of birth has been entered. [6 marks] Note: The following SQL syntax may be useful to accomplish these tasks:  SELECT * FROM tbl_name WHERE col1 = val1; (Where tbl_name, col1, val1 etc. are to be replaced with appropriate values)

Figure 4.1 – Sample HTML form for Question B4 a)

Figure 4.2 – Database Entity-Attribute diagram for Question B4 d)

UC PG 12 15 18 Rating 5 years 10 years 12 years 15 years 18 years Minimum age Figure 4.3 – Age rating categories and minimum age required to buy the game

Answer pointers a) Video Game Rating Search Search Games Enter the game title: Enter your date of birth:

b) i) For a program to operate effectively, correct data is vital. Data validation is important because it is not possible to predict what the user agent will enter into input fields. Data may be corrupt, missing, badly formed or even maliciously designed to exploit weaknesses in the program. Something in the vein of “Invalid username/password combination – please re-check your details and try again”. 0.5 marks should be given for a message such as “Invalid password” (since it gives information that the username might have been correct). c) i) An example of data that should not be regenerated would be passwords - this is because a) the form data may not be transmitted using HTTPS and b) because the password will be visible in the source code of the cached page (which is a potential security risk).

ii)

ii)
$dateOfBirth = $year . "-" . $month . "-" . $day; $ageInSeconds = strtotime("now") – strtotime($dateOfBirth); if $ageInSeconds < 0 { ?> Video Game Rating Search Search Games Enter the game title: