next up previous contents
Next: Acronym Key Up: A Distributed Architecture Definition Previous: COM


Abstraction: A description of a family of systems that is independent of the details of any one particular system. [#!Webster:1992!#]

Abstract Syntax: A description of a data structure that is independent of machine-oriented structures and encodings. [#!RFC:1208!#]

Abstract Syntax Notation One (ASN.1): The language used by the OSI protocols for describing abstract syntax. This language is also used to encode SNMP packets. ASN.1 is defined in ISO documents 8824.2 and 8825.2. [#!RFC:1392!#]

Access Control List (ACL): Most network security systems operate by allowing selective use of services. An Access Control List is the usual means by which access to, and denial of, services is controlled. It is simply a list of the services available, each with a list of the hosts permitted to use the service. [#!RFC:1392!#]

Advanced Research Projects Agency Network (ARPANET): A pioneering long haul network funded by ARPA (now DARPA). It served as the basis for early networking research, as well as a central backbone during the development of the Internet. The ARPANET consisted of individual packet switching computers interconnected by leased lines.

Agent: In the client-server model, the part of the system that performs information preparation and exchange on behalf of a client or server application. [#!RFC:1208!#]

American National Standards Institute (ANSI): This organization is responsible for approving U.S. standards in many areas, including computers and communications. Standards approved by this organization are often called ANSI standards. ANSI is a member of ISO. [#!RFC:1392!#]

American Standard Code for Information Interchange (ASCII): A standard character-to-number encoding widely used in the computer industry. [#!RFC:1392!#]

Application: A program that performs a function directly for a user. [#!RFC:1392!#]

Application Program Interface (API): A set of calling conventions which define how a service is invoked through a software package. [#!RFC:1208!#]

Architecture: The components of a system and their interface behavior.

Atomicity: An action either happens or it does not in total, there is no partial completion.

Authentication: The verification of the identity of a person or process. [#!RFC:1392!#]

Bandwidth: The amount of data that can be sent through a given communications circuit. [#!RFC:1392!#]

Behavior: The responses of the components in a system to each other and other stimulation from the environment.

Big-endian: A format for storage or transmission of binary data in which the most significant bit (or byte) comes first. The term comes from "Gulliver's Travels" by Jonathan Swift. The Lilliputians, being very small, had correspondingly small political problems. The Big-Endian and Little-Endian parties debated over whether soft-boiled eggs should be opened at the big end or the little end. [#!RFC:1208!#]

Binding: The mapping of an abstract name to more detailed representation. The IP address of a computer given the name of the computer is an example of a binding. The port of an application is another example.

Channel: A communication path that guarantees delivery and correct order of data.

Checkpoint: A particular point in a computation where state is written to stable storage. At some later time, the computation may be initialized to this saved state.

Class: The meta structure of an object defining the inheritance of methods and data structures.

Client: A computer system or process that requests a service of another computer system or process. A workstation requesting the contents of a file from a file server is a client of the file server. [#!RFC:1392!#]

Communication: An exchange of information.

Compliance: An implementation is in compliance with a specification when all conditions and expectations hold.

Composition: A technique used to combine smaller components into large components to solve more complex problems.

Connection-oriented: The data communication method in which communication proceeds through three well-defined phases: connection establishment, data transfer, connection release. TCP is a connection-oriented protocol. [#!RFC:1392!#]

Connectionless: The data communication method in which communication occurs between hosts with no previous setup. Packets between two hosts may take different routes, as each is independent of the other. UDP is a connectionless protocol. [#!RFC:1392!#]

Contract: An agreement between two components in a system determining their behavior.

Data: Bases level measurement of uninterrupted information. Example could include integers, floating point numbers, and dates. Data is consumed by analysis techniques which generate information.

Decomposition: A technique used in modeling where more complex systems are separated into smaller less complex systems. This process continues until a system is reached where a know solution exists.

Distributed Computing Environment (DCE): An architecture of standard programming interfaces, conventions, and server functionalities (e.g., naming, distributed file system, remote procedure call) for distributing applications transparently across networks of heterogeneous computers. Promoted and controlled by the Open Software Foundation (OSF), a consortium led by Digital, IBM and Hewlett Packard. [#!RFC:1208!#]

Domain Name System (DNS): The DNS is a general purpose distributed, replicated, data query service. The principal use is the lookup of host IP addresses based on host names. The style of host names now used in the Internet is called "domain name", because they are the style of names used to look up anything in the DNS. [#!RFC:1392!#]

Encapsulation: The technique used by layered protocols in which a layer adds header information to the protocol data from the layer above. [#!RFC:1208!#]

Encryption: Encryption is the manipulation of data in order to prevent any but the intended recipient from reading that data. There are many types of data encryption, and they are the basis of security. [#!RFC:1392!#]

Environment: The underlying system assumptions, resources, contracts, and behaviors as viewed by a component.

Error: A state in computation which leads to unexpected conditions. This is also called a failure or a fault.

Extended Binary Coded Decimal Interchange Code (EBCDIC): A standard character-to-number encoding used primarily by IBM computer systems. [#!RFC:1392!#]

Federation: An organizational technique of a system where many decisions are decentralized and distributed, yet individual members benefit from each others contributions.

Information: Low content data is analyzed generating higher content information.

Interface: The layer between two components in a system.

Invariant: A quantity that does not change during a computation.

International Organization for Standardization (ISO): A voluntary, non-treaty organization founded in 1946 which is responsible for creating international standards in many areas, including computers and communications. Its members are the national standards organizations of the 89 member countries, including ANSI for the U.S. [#!RFC:1392!#]

Kerberos: Kerberos is the security system of MIT's Project Athena. It is based on symmetric key cryptography. See also: encryption. [#!RFC:1392!#]

Little-endian: A format for storage or transmission of binary data in which the least significant byte (bit) comes first. See also: big-endian. [#!RFC:1208!#]

Migration: The moving of one process in a system from one physical location to another.

Name: An identifier, most often unique, to a component in a system.

Name Resolution: The process of using the name to obtain more information.

Name Space: A collection of unique names.

Notification: Awareness of a state change regardless of location.

Object: A component of a system that logically contains both data and methods.

Permission: In security terms, this is the granting of authorization.

Persistence: An component that survives for a long period of time usually associated with data stored on a file system.

Policy: A high-level guideline governing behavior.

Port: A port is a transport layer de-multiplexing value. With Each application is a unique port number. Network packets are first routed to the computer using the IP and then routed to the application using the port number. [#!RFC:1392!#]

Prohibition: An action that is not permitted to happen.

Protocol: A formal description of message formats and the rules two computers must follow to exchange those messages. Protocols can describe low-level details of machine-to-machine interfaces (e.g., the order in which bits and bytes are sent across a wire) or high-level exchanges between allocation programs (e.g., the way in which two programs transfer a file across the Internet). [#!RFC:1392!#]

Quality of Service (QoS): A collection of measurements indicating how well a system is behaving. These might include response time, bandwidth, latency, error rates, recovery time, down time, round-trip-time, and many more.

Refinement: An analysis process which takes one level of a design into a more detailed level.

Remote Procedure Call (RPC): An easy and popular paradigm for implementing the client-server model of distributed computing. In general, a request is sent to a remote system to execute a designated procedure, using arguments supplied, and the result returned to the caller. There are many variations and subtleties in various implementations, resulting in a variety of different RPC protocols. [#!RFC:1208!#]

Request For Comments (RFC): The document series, begun in 1969, which describes the Internet suite of protocols and related experiments. Not all (in fact very few) RFCs describe Internet standards, but all Internet standards are written up as RFCs. The RFC series of documents is unusual in that the proposed protocols are forwarded by the Internet research and development community, acting on their own behalf, as opposed to the formally reviewed and standardized protocols that are promoted by organizations such as CCITT and ANSI. [#!RFC:1392!#]

Security Authority: One component of a system that provides the services of authentication, authorization, integrity, confidentiality, and non-repudiation. This is accomplished using audit trails, encryption, and private and public keys. The four basic behaviors of a security system is to protect, detect, confine, and to mitigate.

Server: The component in a distributed system that provides services.

Signal: A state change that is handled out-of-bounds usually using the mechanism of an interrupt.

State: The items that define a component at a particular time.

Stream: A type of transport service that allows its client to send data in a continuous stream. The transport service will guarantee that all data will be delivered to the other end in the same order as sent and without duplicates. [#!RFC:1392!#]

System: The sum total of all the components, their interfaces and behavior.

Thread: An execution path of computer instructions usually at the control of an application sharing one address space.

Transparency: A component exhibits transparency to a change, if no measurable difference exists before and after the change. Examples of transparency might be different locations, different operating systems, or different protocols.

Type: The class of which the object belongs.

next up previous contents
Next: Acronym Key Up: A Distributed Architecture Definition Previous: COM
Ronald LeRoi Burback