Namespaces

cs3353

Namespace Domain

• A computer system namespace domain is created and maintained to:– standardize the policy for names– prevent name collisions (same names with

different meanings)

Namespace

• The namespace is used to create names for– User IDs– Individual computer systems– Other hardware– Other categories?

• Passwords

Namespace Policy

• Formula• Theme

– All names fit a theme like planet names, cartoon characters, star trek characters, etc.

• Function– The name describes the function: disk_server,

main_printer, etc.

Namespace Policy

• Theme names for hardware are ok when there are only a few systems:– Server = hal9000– Clients = uhura, checkov, sulu, spock, etcManaging a large number of systems this way is

not advised.

Namespace Policy

• Function names: disk_server01, disk_server02, etc.

• Function names have their own maintenance problems: consider what happens when the disk_server is reassigned its role in the computing system to handle e-mail.

Namespace Policy: Formula

• Formula names are not interesting or personal, but are practical for large namespaces.

• Divide the name into fields. Fixed length fields make the names easier to learn.

• Keep the name to a reasonable length.

Namespace Policy: Formula

• Formula names can be used to obscure the function of named entities in the domain.

• Keep the names to a reasonable length unless long names serve a specific purpose.– Longer names tend to be used less frequently

Formula Policy

• User IDs, Passwords• Machine names: clients & servers• Miscellaneous hardware:

– Printers, Fax-machine, etc• Other?

Namespace Formula Policy

• Use any combination of:– Prefix: – Infix:– PostfixTo construct a namespace.

Example: User ID Formula (Prefix)

• Prefix (one letter field)– Regular employee (e)– Consultant/Contractor (c)– Temp (t)– Vendor/Supplier (s | v)– Visitor/Guest (g)– Helpful for identification and access control

Example: User ID Formula (Infix,Postfix)

• Infix (three character field)– Three letters using name initials

• Postfix (two character field)– 00 through 99 if two entities have the same first

four characters.

Example: Namespace Policy (Hardware)

• Computer systems (6 to 8 characters)– Postfix– Infix– Prefix

Example: Namespace Policy (Hardware)

• Postfix– Server (s)– Client (c)– Experimental (e)– Printer (p)– Backup device (b)– Etc.

Example: Formula Namespace (Hardware)

• Infix – 3 character base-36 number: 000-zzz• Postfix – 2 digits Year of purchase (09).

Most hardware is retired within 10 years.

User ID name space

• Possible choices– Full name– Initials and digits– Anonymity of user IDs may be required.– Limit to 8 characters if possible.

User ID name space

• A centralized data base for User ID names is needed.

• A single authentication data base can be used to keep track of User ID name space.

Other Namespace Considerations

• Scope – what is the scope for your namespace. – What is the impact of growth or a merger?

• Security – do the names need to be obscure?

• Reuse – When is it appropriate to re-use a name, if ever?

Changes in the Namespace

• A name change policy is needed.• A central database with a record of all

names in the namespace is required for managing the namespace.

Class Exercise

• Create a formula policy for:– Hardware– User IDs– The formula method can be applied to

passwords