More on Component Services

Component Services

discovery issue with naming

naming only works when you know who you want, not what you want

property

a named value that relates to some feature of a component

satisfaction problem

find a component that meets a client’s constraints expressed in terms of properties

possible approach to finding components from requested properties 1

provide a list of all appropriate components to each possible client in a file

possible approach to finding components from requested properties 2

broadcast to all components asking whether they meet the requirement, choose from the set that say yes

possible approach to finding components from requested properties 3

convert each request into a name and use a naming service to find the best component

possible approach to finding components from requested properties 4

use a specialised service that’s designed to match properties on components

intentional naming

take a set of properties and turn them into a name that can be looked up

comment on intentional naming 1

need a canonical ordering in which to search for properties

comment on intentional naming 2

doesn’t handle ranges well

comment on intentional naming 3

hard to see exactly which components are actually available

comment on intentional naming 4

hard to maintain especially if a component’s properties change

trading service

service that allows clients to request a component with a particular set of properties

benefit of trading service 1

single point of control and evolution

benefit of trading service 2

can make the query language richer more easily

benefit of trading service 3

collects together equivalent components for subsitution