Data Design

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In this step, you will reap the benefit of the work you did in the planning phase. This is where you put to use the information you have painstakingly gathered.

What you have now is a list of data that you will put into your directory. The data has one or more data sources and one or more applications using the data. Because the most important job of the directory is to service applications, it is important to know which applications need what data and where the data comes from. A useful approach is to produce a matrix for each application. The matrix should hold the data name, the data type, the information source, and the data source that has to be considered authoritative. The data type is meant as a human-language description — such as password, e-mail, phone number — and not a C-style type declaration such as int, char, etc. Exhibit 4 shows an example of such a matrix.

Application: Phone Book Administration
Row	Data	Type	Source	Source Owner
1	SurName	String	Admin Software	HR
13	NT Password	Password	NT SysAdmin	IT Sysadmin
21	Phone Number	Phone Number	TELCO SW	Engineering

Exhibit 4: Matrix for Data-Design Process

A mapping between the application and application owner as shown in Exhibit 5 is also very useful. You will then know who owns the data and who owns the application using this data. Both are partners who should be involved in the data design process.

Row	Application	App Owner
1	NT SysAdmin	IT Sysadmin
1	HP System Admin	IT Sysadmin
1	SUN System Admin	IT Sysadmin
1	Phone Admin	Engineering
Row	Application	App Owner
31	Web Pages HR	WEB TEAM
31	Phone Accounting	Engineering
Row	Application	App Owner
21	PhoneBook	WEB TEAM
21	Phone Accounting	Engineering

Exhibit 5: Mapping between Applications and Application Owner

Once you have documented all applications in this way, you can put this information together in another matrix describing what data the directory should hold. In this matrix, you will list the data name and data type along with the following information:

• Applications that put the data in

• Owner of the data, i.e., the entity that is responsible for maintaining the data

• Whether the data is publicly readable

• Whether a human user can modify personal data (e.g., password, "yes"; salary, "no")

• Who can update the data

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