Classes of Information Resource Management
Three types of information systems:
Information-Retrieval Systems (IR)
Search large bodies of information which are not specifically formatted as formal data bases. Web search engine Keyword search of a text base Typically read-only Relatively small schema Large body of homogeneous data Minor or no deductive capability Extensive formal update capability Shared use for both read and write Relatively small body of heterogeneous information Significant deductive capability Typical use: support of an intelligent application.
Database Management Systems (DBMS)
Knowledge-Base Systems (KB S)
20061029: slides 1 of 12
Key DBMS issues:
Efficiency issues:
Databases can be very large. Efficient access must be provided despite the size.
Simplicity issues:
Many potential users are not sophisticated programmers, and so simple means of access must be available. Means of more sophisticated access must also be available.
Multi-user issues:
Concurrency Several users may have simultaneous access to the database. Access via views Each user has a limited “window” through which the appropriate part of the database is viewed. Authorization The access privileges of each user will be limited in a specific way.
Robustness issues:
Deadlock must be avoided. A means of recovery from crashes, with minimal loss of data, must be available.
20061029: slides 2 of 12
Data Model Evolution:
Model
File management Navigational models Relational model
Devel.
Use
Properties
Some data independence, but the model invites dependence. Requires procedural queries. Simple, easy to use for non-experts. Strong data independence. Standard nonprocedural query language (SQL). Excellent implementations exist. Limited expressive capability. Powerful expressive capability, but require substantial expertise for use. Popular in niche applications. Standardization not
Information-Retrieval Systems (IR)
Search large bodies of information which are not specifically formatted as formal data bases. Web search engine Keyword search of a text base Typically read-only Relatively small schema Large body of homogeneous data Minor or no deductive capability Extensive formal update capability Shared use for both read and write Relatively small body of heterogeneous information Significant deductive capability Typical use: support of an intelligent application.
Database Management Systems (DBMS)
Knowledge-Base Systems (KB S)
20061029: slides 1 of 12
Key DBMS issues:
Efficiency issues:
Databases can be very large. Efficient access must be provided despite the size.
Simplicity issues:
Many potential users are not sophisticated programmers, and so simple means of access must be available. Means of more sophisticated access must also be available.
Multi-user issues:
Concurrency Several users may have simultaneous access to the database. Access via views Each user has a limited “window” through which the appropriate part of the database is viewed. Authorization The access privileges of each user will be limited in a specific way.
Robustness issues:
Deadlock must be avoided. A means of recovery from crashes, with minimal loss of data, must be available.
20061029: slides 2 of 12
Data Model Evolution:
Model
File management Navigational models Relational model
Devel.
Use
Properties
Some data independence, but the model invites dependence. Requires procedural queries. Simple, easy to use for non-experts. Strong data independence. Standard nonprocedural query language (SQL). Excellent implementations exist. Limited expressive capability. Powerful expressive capability, but require substantial expertise for use. Popular in niche applications. Standardization not