User interface managers, interface components and re-use

User interface managers are separate software components for use in interactive systems. They support executable specifications of the user interface, and perhaps its linkage to the non-interactive core of the underlying application. User interface managers themselves have a component substructure. In closed toolboxes of objects, these components are characterised by style-commitment. Interaction policy and physical appearance are embedded in the implementation mechanism of objects. The author has developed a linked pipelines model, which is a complete model of interactive systems based on information flow analysis. It is formal in both its form and its formation.. Designer effort and re-usability are orthogonal, save for a practical possibility that pre-configured menu objects will be more (re-)used than unconfigured abstractions, because they initially require less effort to use. However, the benefits of programmer productivity need to be balanced against the usability for end-users of pre-configured objects. The proposal is that with good software tools based on powerful style-independent abstract components, the time to configure a required object will be less than the time required for programmers to familiarise themselves with over-configured, idiosyncratic, inflexible toolkit objects. Higher level, style-independent components are, of their very nature, an open architecture, and thus allow flexible responses to user needs. Toolkits generally do not possess these properties. Re-usability for the programmer is nothing if it does not bring usability for the end-user. Flexible, open architectures for user interface managers have the advantage of not ruling this out.<>