Application Platform Service Qualities

Principles    Taxonomy

Principles

Besides the platform service categories delineated by functional category, service qualities affect information system architectures. A service quality describes a behavior such as adaptability or manageability. Service qualities have a pervasive effect on the operation of most or all of the functional service categories. 

The discussion of service qualities is consolidated here in a single location in order to provide a coherent perspective.

In general a requirement for a given level of a particular service quality requires one or more functional service categories to co-operate in achieving the objective. Usually this means that the software building blocks that implement the functional services contain software which contributes to the implementation of the quality.

For the quality to be provided properly, all relevant functional services must have been designed to support it. Service qualities may also require support from software in the Application Software entity and the External Environment as well as the Application Platform.

In some cases, a service quality affects each of the service categories in a similar fashion, while in other cases, the service quality has a unique influence on one particular service category. For instance, international operation depends on most of the service categories in the same way, both providing facilities and needing their co-operation for localization of messages, fonts and other features of a locale, but it may have a more profound effect on the software engineering services, where facilities for producing internationalized software may be required.

During the process of architecture development, the architect must be aware of the existence of qualities and the extent of their influence on the choice of software building blocks used in implementing the architecture. The best way of making sure that qualities are not forgotten is to create a quality matrix, describing the relationships between each functional service and the qualities that influence it. 

Taxonomy of Service Qualities

The service qualities presently identified are:

• Availability (the degree to which something is available for use), including:
  • manageability, the ability to gather information about the state of something and to control it
  • serviceability, the ability to identify problems and take corrective action such as to repair or upgrade a component in a running system
  • performance, the ability of a component to perform its tasks in an appropriate time
  • reliability, or resistance to failure
  • recoverability, or the ability to restore a system to a working state after an interruption
  • locatability, the ability of a system to be found when needed

• Assurance, including:
  • security, or the protection of information from unauthorized access
  • integrity, or the assurance that data has not been corrupted
  • credibility, or the level of trust in the integrity of the system and its data

• Usability, or ease of operation by users, including:
  • International operation, including multilingual and multicultural abilities

• Adaptability, including:
  • interoperability, whether within or outside the organization (for instance interoperability of calendaring or scheduling functions may be key to the usefulness of a system)
  • scalability, the ability of a component to grow or shrink its performance or capacity appropriately to the demands of the environment in which it operates
  • portability, of data, people, applications, and components
  • extensibility, or the ability to accept new functionality
  • the ability to offer access to services in new paradigms such as object orientation.

Copyright © The Open Group, 1998