Desired Quality The ability of the system to be fully or partly operational
as and when required and to effectively handle failures
that could affect system availabilityTactics Select fault-tolerant hardware
Use high-availability clustering and load balancing
Log transactions
Apply software availability solutions
Select or create fault-tolerant software
Design for failure
Allow for component replication
Relax transactional consistency
Identify backup and disaster recovery solution
Table 28 Tactics addressing Availability and ResilienceIn this Section design choices are presented that apply most of the tactics listed
in Table 29. The tactics not considered here are given at the end of this Section
with an explanation why they have been omitted. Table 29 presents for each
tactic one or more architectural design choices together with their impact on the
architectural views introduced in Section 4.2.
Tactic
Impact on ViewsFunctional Information Deployment and OperationUse high
availability
clustering
VE Resolution
location-oriented (DC
A.1) [De 2012]Information Model
requires data type for
defining scope for
location of interestVE Resolution instances
for each location clusterVE Resolution
domain-oriented (DC
A.2) [De 2012]Information Model
needs data type for
defining types of
resourcesResolution framework is
organised hierarchicallyVE Resolution
Semantic Web-
oriented (DC A.3)
[De 2012]Information model
needs to be encoded
according to Semantic
Web standardsSearch space of
resolution framework
needs to be indexed by
certain machine-learning
techniqueVE Resolution Peer-
to-Peer-oriented (DC
A.4) [De 2012]No impact No centralised server neededUse load
balancing
Requires function
that monitors load of
components and
triggers load
balancing algorithmComponent
descriptions need
metric to measure
current work load and
defined load limits―Scaling out‖ approach -
additional clones of
components need to be
available (DC A.5)