Welcome to the 2006/7 PAFSD course.
This blog will be used to supplement the unit website at:
http://www.tech.port.ac.uk/staffweb/chandlej/PAFSD.html
and to provide a forum for discussing the material covered in the lectures.
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LESSON 1
SOFTWARE PATTERNS
Patterns from my point of view are problems put in a context and have solutions. Come to think about it everything we do in our daily life is a pattern in that they are similar situations that need to be dealt with day in day out in the same way. For there to be a pattern we got to have a recurring problem and a useful solution and the solution should be replicated by others when it is appropriate. Understanding the problem is a key part of understanding the solution. Focusing on triggers (forces) for problems also helps us to focus on the core solution. We should also think of when we would not use the pattern this is in case the context has changed.
Technology threatens to change processes more often than expected and it is in these situations that patters come in handy. During the invention of patterns by Christopher Alexander in the late 1970s he must have observed everyone coming up with there own but same solutions to the problem every time. Without proper documentation then the results might have been slightly different. Patterns kind of play the role of keeping a standard of how problems with similar contexts are solved, they are reusable, enable us to work smarter and easy to use.
Software patterns are therefore engineering problems put in a context and has software solutions.
PATTERN IN REAL LIFE
Problem: How to quickly find a product in a supermarket
Solution: Send a text using a mobile phone and receive information on a product’s location in store and price
Context:
You are a loyal customer to the Tesco supermarket stores and you need to purchase some products from one of their large stores as fast as you can. You are not familiar with this particular store. There seems to be no staff on the floor that could quickly assist you in getting to the products you are looking for. Asking the staff at the customer care desk for help will waste more of your time because they will walk you back around the aisles looking for the product or call someone else to get the information. Following the signs on each aisle does not help much because the aisles are too long and the sign only categorises what is on that aisle, sometimes you will find the product is out of stock yet you are up and down looking for it. You have limited time because you have an important meeting to attend. You don’t need to go round the store because you do not want to buy what is not on your list. You could go for your meeting and later order the products online when you get home but some products are not on the online catalogue, some of the products you are buying need you to examine and choose for example meat or vegetables. You need the products tonight, ordering online will mean next day delivery and you will be at work. You can get some of these products from the other small stores but theirs is never value for money but last option shopping store and they are obviously expensive. Borrowing some of what you want from your neighbour is not an option either because he’s never there. Your workmates sometimes call Tesco stores just to enquire about if the product is in store, find out what side it is and maybe the price of the product but you have no access to the phone considering that the response is not instant.
Examples/known use: It might take 30 seconds to receive reply on location of product in store and its price.
Related Patterns: Assistance by staff, Come early enough, shop online, call customer service.
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