| In Chapter 18, Maintaining Data, we discussed the importance of managing directory data to keep it accurate and up-to-date. The reasons to do so are simple, and they all boil down to increasing the usefulness of the directory service. The arguments for directory coexistence are similar, but they are motivated by the fact that you may have many data sources that contain useful, related data. Chances are that many directories, databases, and other data sources are already deployed in your organization. Here is a list of common data sources: -
Network operating system ( NOS ) directories . These include most deployments of Novell eDirectory, Microsoft Active Directory, and Unix's Network Information Service (NIS). These directories typically contain minimal information about users (such as name , login ID, and password) and information about devices and services related to operating systems (such as printers and file servers). The main job of these directories is to serve the needs of the network operating system in which they are embedded. Although quite adept at that task, most of these directories make poor general-purpose directories because of their lack of flexibility and specialized feature set; certainly it is difficult to use a single deployment of these directories as an enterprisewide directory and as the operating system directory. However, NOS directories often do contain information that might be useful in an enterprise or extranet directory, such as people's names and login IDs. -
Application-specific directories . These include the Lotus Notes name and address book, Microsoft's Exchange directory, Novell's GroupWise directory, the built-in authentication databases provided with most network services, and other directories that are designed to meet the needs of a single application. These directories sometimes are accessible only via proprietary protocols or application programming interfaces (APIs), seldom are extensible, and like NOS directories, typically make poor general-purpose directories. However, also like NOS directories, application-specific directories may contain information you would like to make available in an enterprise or extranet directory. -
Corporate databases . This broad category refers to databases that hold information about people (human resources), telephone operations, customers, payroll, and so on. These databases often contain a lot of interesting and useful information that should be made available through your general-purpose, enterprise directory service. Corporate databases are also usually integrated with existing business processes, from hiring and termination of employees to procurement and financial processes. -
External databases . External databases are not maintained within or by your organization; they live outside your corporate firewall (literally or figuratively) and are maintained by another organization. Like corporate databases, these data sources may hold useful information about people and resources ”for example, from some of your corporate partners . However, it is rare (but not unheard of) to integrate data sources across corporate boundaries. -
Homegrown databases . As the name suggests, this category refers to the inevitable collection of ad hoc databases present in all organizations. Homegrown databases might be maintained by departmental secretaries or local administrators, or they might have been created for projects that have since been abandoned . For example, in many companies a secretary or an administrative assistant maintains a spreadsheet that contains up-to-date information about all employees that work in his department. You will need to determine how many of these databases exist in your organization and whether any of them contain information that should be included in your directory service. -
The directory service itself . Some data may be maintained only in your directory service, either by administrators or by end users. If so, new data will flow from various LDAP clients back to your directory servers. For example, you might allow users to update their own contact information, such as home address and telephone number, directly in the directory, or you might ask administrative assistants to maintain departmental information such as fax phone numbers . It might be useful to allow this data not only to be published in the directory, but also to flow back to your human resources database. All the data sources in your organization serve a purpose (or did at one time). Some of them may be in the process of being phased out; others are there to stay. Why should you be concerned about making your directory service coexist with these other data sources? Here are several reasons: -
Jump-starting your directory . One of the problems you face, as discussed in Chapter 7, Data Design, is how to populate your directory with useful data. The best and easiest way to do this is to find another data source that already contains the data you want. Importing data from an existing source can save you substantial time and money in getting your directory populated with data. -
Ease of data maintenance . As discussed in Chapter 18, Maintaining Data, it is important to keep the data in your directory accurate and up-to-date. Feeding your directory periodically from existing data sources can help achieve this goal. This arrangement can save you from having to institute complicated update procedures yourself. Instead, you can simply track changes made to the data in the source database. -
Avoiding duplicated data . Maintaining data in multiple locations leads to inconsistencies, duplicated effort, increased costs, and a variety of other problems. Using directory coexistence to maintain data in a single location but make that data available everywhere it is needed helps reduce costs and problems. -
Avoiding user confusion . Duplicated data often leads to confusion among users. Users often assume (reasonably so) that if they change a piece of information about themselves in one place, the same change will be made in all other locations. Your users will be confused and unhappy if they find that a change of address made in the human resources database needs to be made again in your enterprise directory. As you can see, directory coexistence is a large, complex area. Developing a good coexistence strategy is not an easy task, but it can pay big dividends . |
