Building a Yii app: The Data Model

A friend of mine needs a web application to be revamped. I had originally created it about 2 years back using a custom PHP mini-framework that I had built for many projects at that time. The development had stopped for different reasons and parts of his web application were incomplete. For example images were not upload to Amazon S3, which was originally planned. Some Model edits were not working in many parts and there were some data validation issue. He has been doing the groundwork for his business and now has decided to finally complete the application.

The application is related to Medical needs, information about patients, doctors, hospitals etc. I have decided to make the new version using Yii, since some other developer will take over if the project is successful and Yii (or other popular frameworks) is a very well documented framework for anyone to use. The choice of Yii against other PHP frameworks is rather just an impulsive one. I have read comparisons of the good PHP frameworks and Yii is among the top few. Anyway moving on...

While I am building this application, which is a moderately feature rich one, I intend to write about my experiences. Hope this helps anyone looking for a quick introduction and example for Yii. I am trying to make this a tutorial for Yii, I will try my best here. The project needs data for multiple types:

• General User Profile (could be a patient)
• Doctor
• Hospital
• Nursing Home
• Other Medical companies like: Medical Shop, Diagnostic Center, Fitness Center, Ambulance Provider, Nurse, etc.

Other information include:

• Specialization: this is related to Doctors, explained below
• Address: City, State, Country, etc. Any entity can have multiple addresses
• Phone: can be either a fixed or a mobile (cellular) phone. Any entity can have multiple phones, also address can have phones associated with them
• Department: Hospitals or Nursing Homes can specify many departments
• Branch: Hospitals, Nursing Homes of Other companies can have multiple locations/branches.
• Image: multiple images for any entity.
• User: this is used for authentication, simple email/password for now.

In order to manage the mappings of many entity types to Address, Phone, Branch, Image etc. I have used a central Entity table. Every type of physical entity has an entry in the Entity table (including each branch). Then Address, Phone, Branch, Image, Department are mapped to Entity table.

In Yii terms the relations look like this:

• Doctors can have one or more Specialization (HAS_MANY in Yii Model)
• Doctor, Hospital, Nursing Home, Other, Profile have a one-to-one mapping to Entity (BELONGS_TO in Yii)
• Entity can have multiple Addresses, Phones, Images (HAS_MANY in Yii)
• Entity can have many Departments (HAS_MANY). This is limited to only Hospital, Nursing Home or Other types though at the application level.
• Entity can have another Entity as Branch (HS_MANY). This is also limited to Hospital, Nursing Home or Other types at the application level.

I will write about setting up Yii Models in the next blog entry...

Dummies Introduction to Amazon Web Services

Lot of you may have heard of this. Well certainly you have heard of Amazon.com and if you are into software/IT/web there is a good chance someone in your company is thinking of that mumbo jambo called cloud computing. Well what the hell is all this and then this web services?

Note: most of what I do is related to running websites. So whatever I write here will also relate to that. Beyond that I don't know nothing :|

Cloud Computing Well there is this thing called a computer. You know it right. And you know that you need them to run your websites or web apps or what else you call them. So what choices do you have? Well here are some:

1. you can take a shared hosting account
2. can take a dedicated server
3. you can take a hosted option to run your website
4. host the website from your own home/office
5. get virtual dedicated server (its like a small slice out of a server, each slice is independent of the other at the OS layer) (short: vds)
6. or you can take a cloud service

So you can assume the cloud service is maybe not radically different from the other options. I mean it still has to run your site or app. It just differs by the way you get the service, manage it, use it. Lets understand an example:

I need to host this blog.

I can take a shared hosting account which will allow me to run a site on a server that is being shared among many other users. Each user is running from his/her own folder. Each having maybe a few MySQL or similar database server users. Some hosts will allow to use a custom .htaccess file in your folder to use custom re-write rules etc. under Apache.

Now that seems a headache for a site which is just running a blog? Well take an account from WordPress.com or Blogger, LJ, etc. These are the hosted options.

I could also take a full dedicated server or a virtual server if I need, but I will to maintain it myself. Also getting a fully dedicated server setup takes sometime (1 day or more). The last option is that I take a cloud service. What I get is an independent slice like in a virtual dedicated host. But its more. A basic cloud service should give me access to the service fast. So a new slice fitted with 1GB or RAM/X Ghz of processor etc. should be up in just a few minutes maybe. This is same in vds. The most important part: all the setup, settings should be available through APIs. What was that? Well I should have a simple protocol (mostly http based) which I or my custom code or some app can access to create a new slice, or get a bigger slice if available, check status, and maybe other stuff. That is the most important part. The ability for software itself to create its own environment to run on! Confused? Even I am :P ... well don't worry, I will explain.

Now there are many examples of cloud services, but I have (sadly) enough exposure in just one: Amazon Web Services. So lets dig into it.

Amazon Web Services

Main website

Services listing:

Amazon Elastic Compute Cloud (Amazon EC2):

This is our primary service and we will inspect this first. In brief this is the service that allows you to get a server (hardwarde + software full stack as needed) up and running in little time, assign an IP address to it, set firewall and invite users to the website. Well except for the invite part the rest are all provided by Amazon and over an API. So my PHP code coulf do that! Of course I will be billed for it.

Amazon Simple Storage Service (Amazon S3):

Just store whatever you needed, setup access rules, and forget about it. Simple!

Amazon CloudFront:

This of these as the equivalent to you local post offices. So you do not need to go to the city central post office to fetch something. Local distribution of data! Its fast way to get things to the audience.

Well there are other services but I am not as good with them. When I experiment/use them enough I will blog on them.