Entity-Relationships Model for Ajaqs

Entity-Entity Matrix for Ajaqs Showing Cardinality of Relationships
	FaqUser	Role	Project	Faq	Question	Answer	Attachment
FaqUser		N:N	N:N		1:N	1:N	1:N
Role	N:N
Project	N:N			1:N
Faq			N:1		1:N
Question	N:1			N:1		1:N
Answer	N:1				N:1		1:N
Attachment	N:1					N:1

Note: To resolve the many-to-many relationship between the FaqUser and Project entities, we create an intermediate (i.e., associative) entity called the UserProject. See the E-R Diagram below.

The E-R Diagram for Ajaqs

In this diagram, we follow conventions outlined in the article at http://www.utexas.edu/cc/database/datamodeling/index.html. The image of the diagram was produced by dia-0.90, a free software package that you can download from http://freshmeat.net.

Size Limits for Entity Fields

The following table shows what size limitations exist for certain entity fields, depending on the database vendor:

Entity	Field	MySQL	PostgreSQL
FaqUser	logon	32 chars	32 chars
FaqUser	password	32 chars	32 chars
FaqUser	email	128 chars	128 chars
Role	role	32 chars	32 chars
Project	name	64 chars	64 chars
Faq	name	64 chars	64 chars
Question	question	64 Kb	Unknown
Answer	answer	64 Kb	Unknown
Attachment	attachment	16 Mb	Unknown
Attachment	fileName	128 chars	128 chars
Attachment	fileType	64 chars	64 chars