37. SQLALCHEMY + URL DISPATCH WIKI TUTORIAL

37.2 Design

Following is a quick overview of the design of our wiki application, to help us understand the changes that we will be making as we work through the tutorial.

37.2.1 Overall

We choose to use reStructuredText markup in the wiki text. Translation from reStructuredText to HTML is provided by the widely used docutils Python module. We will add this module in the dependency list on the project setup.py file.

37.2.2 Models

We’ll be using a SQLite database to hold our wiki data, and we’ll be using SQLAlchemy to access the data in this database.

Within the database, we define a single table named tables, whose elements will store the wiki pages. There are two columns: name and data.

URLs like /PageName will try to find an element in the table that has a corresponding name.

To add a page to the wiki, a new row is created and the text is stored in data.

A page named FrontPage containing the text This is the front page, will be created when the storage is initialized, and will be used as the wiki home page.

37.2.3 Views

There will be four views to handle the normal operations of adding and editing wiki pages, and viewing pages and the wiki front page. Two additional views will handle the login and logout tasks related to security.

440

37.2. DESIGN

37.2.4 Security

We’ll eventually be adding security to our application. The components we’ll use to do this are below.

• USERS, a dictionary mapping users names to their corresponding passwords.

• GROUPS, a dictionary mapping user names to a list of groups they belong to.

• groupfinder, an authorization callback that looks up USERS and GROUPS. It will be provided

	in a new security.py file.
•	An ACL is attached to the root resource. Each row below details an ACE:
	Action	Principal	Permission
	Allow	Everyone	View
	Allow	group:editors	Edit
•	Permission declarations are added to the views to assert the security policies as each request is
	handled.

37.2.5 Summary

The URL, actions, template and permission associated to each view are listed in the following table:

441

37. SQLALCHEMY + URL DISPATCH WIKI TUTORIAL

URL	Action					View	Template	Permission
/	Redirect		to	/Front-		view_wiki
	Page
/PageName	Display			existing		view_page 2	view.pt	view
	page 1
/edit_page/PageName	Display		edit		form	edit_page	edit.pt	edit
	with	existing			con-
	tent.
	If the form was sub-
	mitted,		redirect to
	/PageName
/add_page/PageName	Create		the		page	add_page	edit.pt	edit
	PageName in				stor-
	age,	display			the
	edit	form		without
	content.
	If the form was sub-
	mitted,		redirect to
	/PageName
/login	Display login form.					login	login.pt
	If the		form		was
	submitted, authenti-
	cate.
	•	If authentica-
		tion success-
		ful,		redirect
		to	the		page
		that we came
		from.
	•	If	authenti-
		cation			fails,
		display			login
		form			with
		“login failed”
		message.
/logout	Redirect		to	/Front-		logout
	Page

442