Mark's IT Blog

Internet Application Development week 6, an introduction to C#.

The fist part of the lecture covered the basic data types and operators (most of which are the same as Java). Control structures and operators came next, again these reflected Java very closely.

Internet Application Development week 6, an introduction to C#.

The fist part of the lecture covered the basic data types and operators (most of which are the same as Java). Control structures and operators came next, again these reflected Java very closely.

Collections in the C-Sharp language are again a mirror of the Java language.

Functions are the methods of Java:

To give a feel for the syntax and a useful tool, the code snippet below draws a table of web server information dynamically.

Week 6 of case study consisted of a lecture and tutorial by Enjoo Lim. The lecture reviewed the basics of Database design which was a nice refresher. Points covered were:

• Conceptual modelling
• Logical modelling
• 1st normal form
• 2nd normal form
• 3rd normal form

After last semesters assignments going to BCNF is a fairly straight forward operation. From our experience on this assignment it is clear that if you dont get the conceptual model right none of the subsequent stages will go smoothly.

The tutorial gave us some time to work in our teams on the task due the following week. At the time of writing this I am compiling our Functional Specification report. There is a clear difference in the level of each teams memebers submissions, to the level that to attain and even level throughout the report would require redoing entire sections. From doing this assigmnet I have found that Object Oriented modelling for Web sites does not fit the same as for a stand alone java program. I will need to do some research on modelling for web systems.

Data Communication, week 5 was unfortunately a  missed class for me due to illness. A summary of the lecture on Network and Transport layers are as follows:

• TCP/IP!

• Review of three-way handshake conducted by TCP
• User Datagram Protocol [UDP]
• IP packet contents:

• Addresses and subnets
• MAC addresses
• Address resolution ARP
• DNS processes

Week 5 of grid computing comprised of a lecture focusing on data transfer protocols for the grid environment. The tutorial returned to the Grid Security Infrastructure [GSI] covered in the previous weeks lecture.

The lecture covered 4 protocols for data transfer within a grid:

• GridFTP
• SCTP
• Fast TCP
• Sensor networks

GridFTP allows for 3rd party transfers which is the major practical difference apart from transfer speed.

We delved into the methods by which these protocols provide advantages over standard file transfer. One question this raised in my mind was why these protocols aren’t the standard if they are superior. I guess the answer to this question lies in the need for most server to try and limit the amount of bandwidth the provide to individuals.

The first assignment for this subject is due this week, I found the specification a little bit vague and am concerned that my report will not hold enough technical details. The lack of technical detail has revealed that my depth of knowledge for this subject is not very sound so it will be a priority over the mid semester break to get some books and clarify my understanding.

Week 5 of Internet Application Development began our move towards dynamic page development. The topics covered were:

• HTTP protocol review
• HTML forms review
• ASP.NET Standard server controls
• Event driven programming and postback

As HTTP has been covered in detail through FIT9020 Data Communications I will skip this topic, noting that it is a stateless protocol. The diagram below illustrates how asp.net pages are processed from HTTP requests:

In week 5 of Case Study we discussed risk. There are a number of risks associated with system development, most stemming from:

• communication between client and  developers
• team issues within development team
• inability of client to clearly define and agree on system requirements

Reviewing these risking and mitigating or managing them is critical for the success of system development.

In regards to Project we are working on as a team I am really finding that it is taking too much of my study time for the lesson that working in teams is difficult. At present my main goal for the unit is to pass whilst preventing it from adversely affecting my grades for other subjects.

The Data link Layer was covered in week 4 of Data communications, which was another high detail lecture [All Trains Now Depart Promptly -> Application, Transport, Network, Data Link, Physical] .

Using both Logical Link Control [LLC] and Media Access Control [MAC] the Data Link layer controls when computers transmit data, detects and correct transmission errors and identifies the beginning and end of messages.

Grid Computing’s week 4 lecture took a security theme covering the Grid Security Infrastructure [GSI], Public key infrastructure , Digital certificates, Mutual authentication, My Proxy and shibboleth.

GSI (see: http://en.wikipedia.org/wiki/Grid_Security_Infrastructure) is an overlay on the transport security protocol (SSL) utilizing asymmetric encryption and the public key infrastructure to acheive:

• Authentication
• Data integrity verification
• Single sign-on
• Inter-organisation decentralized security

All grid entities (user and processes) must have a public key certificate, for more info on public key certificates see: http://en.wikipedia.org/wiki/Public_key_certificate

GSI uses the X.509 standard which included 4 primary pieces of information:

• subject name
• public key
• identity
• digital signature

An illustration of the public key infrastructure process:

Scenario 1 -> privacy, only user can decrypt incoming data

Scenario 2 -> authentication, receivers decrypt data using the sources public key this ensures the data is coming from the correct source

Certificate authorities are required to ensure validity of public and private keys that make the users digital certificate

Unfortunatly I missed the presentation of week 4’s Internet Application Development lecture, I will however make a summary from the note provided. The topics covered were:

• Static vs Dynamic pages
• Development environment for ASP.NET
• IIS virtual directories 

From previous weeks, I seem to keep forgetting the difference between simple and complex types. An easy definition to remember:

In XML Schema, there is a basic difference between complex types which allow elements in their content and may carry attributes, and simple types which cannot have element content and cannot carry attributes.

source: http://www.w3.org/TR/xmlschema-0/

Case study’s fourth seminar analyzed the Functional Requirements Document,  ensuring student have the knowledge to complete task 3.

The main features of a Functional requirements document are:

• • Database design
  • Business Logic Layer design (Best completed using UML in most cases)
  • Interface design
  • System requirements

The purpose of a Functional Requirements document is to reconcile what the client wants and what you plan to build. Once a client signs of on a Functional Requirements document, system design can be completed.

In the tutorial we continued work on our own Functional Requirements doc, after working on it almost all weekend I am still only about halfway through…

Time dedication to this subject was also discussed in the tutorial, I understand there is no exam for the subject so we should be spending more time on it. At present I am spending about 75% of my study time on this subject which is an issue for me. Will try and get most of the work done this week so I can complete other subject assignment next weekend!