Glossary

For a proper and gradual introduction of the concepts behind AppLogic, please see the AppLogic Overview and the User Manual? documents.

This Glossary is currently under construction. It only lists the terms, but we haven't gotten around to explaining them in a short form appropriate for glossaries. See AppLogic Overview, Application Model, ADL Language Reference or the Infrastructure Editor topics for more information until the Glossary is filled in (feel free to try your hand at defining some of the terms here).

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A

ADL

Application Description Language. A structure description language used to capture the design of distributed applications in AppLogic. ADL is used to represent application infrastructure in text form. It is semantically equivalent to XML, but is significantly more suitable for humans. See ADL Language Reference for details.

appliance

See also simple appliance and assembly. A self-contained virtual environment that provides a particular function inside an application. Appliances can be simple or assemblies. The term appliance can be used to denote either the appliance class or an instance of it.

application

A unit of execution on the grid. An application consists of one or more appliances and contains its full infrastructure, configuration and user data. An application can be a template or an instance. Templates can be used to provision multiple instances.

application boundary

the class boundary of the application as an appliance class (the predefined singleton class main). See also class boundary and interior.

application instance

A particular copy of an application that is fully configured and can be run on the grid.

application template

A partially configured application that is used as a template for provisioning application instances.

application volume

A named virtual volume attached directly to an application. Application volumes are most often used to deploy HTML files, static content, scripts, code and databases that are specific to the particular application. An application volume is typically used in conjunction with a virtual appliance, which is configured with the name of the volume and a directory path on that volume from which the appliance should access the content it requires.

assembly

An assembly is an appliance that is composed out of other appliances.. See also appliance. Contrast with simple appliance.

attribute (in appliances)

A value that affects the way the system schedules and runs the appliance. Contrast with property.

attribute (in ADL)

x. See also ADL Language Reference.

B

boundary

The boundary includes everything necessary to configure the appliance, bind it to data on external storage volumes and connect it to other appliances.. See also class boundary and application boundary. Contrast with interior.

boundary property

a property defined on the boundary of a class or assembly.

boundary volume

a placeholder volume defined on the boundary of a class or assembly.

C

catalog

A library package that contains one or more appliance classes. See also global catalog, local catalog.

catalog class

A class within a global or local catalog that can be used to create appliance instances. Contrast with singleton class.

class

A class is a definition of an appliance, consisting of boundary and volumes, that can be used to create appliance instances. See also catalog class and singleton class. Contrast with instance.

class boundary

all attributes of a class visible from outside. The class boundary of AppLogic appliances includes the class name, terminals, volumes, resources and properties. Both simple appliances and assemblies have boundaries. See also application boundary. Contrast with interior.

class volume

A volume that is provided as part of the class definition of an appliance and instantiated whenever an instance of the appliance is created. See also virtual volume, instantiable volume, common volume, null volume. Contrast with placeholder volume.

common volume

A volume that is provided as part of the class definition of an appliance, but is not instantiated when an instance of the appliance is created. See also class volume. Contrast with instantiable volume and null volume.

component

A running instance of an appliance class.

D

default interface

A network interface which gives you the ability to log onto the appliance, install software and troubleshoot it, the same way you would do with any remote server. See also external interface. Contrast with terminal.

deploy

Create an application template or application instance on a grid, by deploying the application's code, content and data onto the grid infrastructure.

E

external interface

A network interface that provides access to the running appliance from the outside world. See also default interface. Contrast with terminal.

F

failover group

An identifier that prevents components within the same failover group from being scheduled on the same physical server device(so that in case of hardware failure, some of them remain alive).

field engineering code

Enables diagnostic or special features of AppLogic. See Field Engineering Codes for details.

G

global catalog

A library package containing one or more appliance classes that may be used in one or more applications. Contrast with local catalog.

H

I

input

Terminal for accepting network connections. See also terminal and interface. Contrast with output.

instance

Instance of an appliance class that is used in a particular application. See also appliance. Contrast with class.

instantiable volume

A class volume that is instantiated (i.e., copied) when an instance of the appliance class is created. See also class volume. Contrast with common volume and null volume.

interface

A unique connection point within the AppLogic system. See also terminal, external interface, default interface.

interior

A structure of virtual appliances defined within an assembly. Contrast with boundary.

J

K

L

local catalog

A library package containing one or more appliance classes that may be used within the application where the local catalog resides. Contrast with global catalog.

M

migration

The process of moving an entity from one physical server device to another.

N

null volume

A class volume where no volume image is provided. See also class volume. Contrast with instantiable volume and common volume.

O

output

Terminal for originating network connections. See also terminal and interface. Contrast with input.

P

placeholder volume

A predefined slot for a storage volume. The slot is filled by configuring the appliance with the name of a volume to mount. Contrast with class volume.

property

A configuration parameter of a class that is specific for each instance of an appliance class that is created.

provision (application)

Create an instance of an application from a template. A provisioned application can be assigned resources, configured, and run on the grid.

provision (grid)

Create a new grid from a set of physical servers.

Q

R

resources

Physical computing resources, like CPU, memory, storage, etc., that can be provided to an appliance or application for its execution.

S

server

x

singleton, singleton class

A class that are limited to a single instance at a time. Contrast with catalog class.

simple appliance

A simple appliance consists of a single virtual environment. It comprises a virtual machine, virtual volumes and virtual network interfaces. It runs its own copy of an operating system (e.g., Linux) and appliance-specific software. See also appliance. Contrast with assembly.

standby

An appliance attribute specifying that an appliance is not to be started automatically when the application is started.

start order

A subordinate attribute which defines the order of starting this subordinate, relative to the other subordinates in the same assembly. Lower numbers are started first and those with a higher number are not started until all those with lower numbers have started successfully.

subordinate

A component within an assembly. See also instance.

T

terminal

A connection point for logical interactions between appliances. See also input and output. Contrast with external interface and default interface.

U

V

virtual volume

A logical disk exposed by one of the servers in the grid and accessible from virtual machines running on any server.

volume

See also virtual volume, class volume, placeholder volume, as well as boundary volume and application volume.

W

X

Y

Z

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-- BeckyH - 26 May 2006