Software Confederations and the Maintenance of Global Software Systems Jaroslav Král, Michal Žemlička Charles University, Prague

Large Organizations (LO) Examples: –International enterprises –State and municipal administrative Features: –Autonomous subunits with autonomous IS –Lots of different activities –Possible reorganizations –Distributed over large area –Changing set of partners (business partners, state authorities)

What is Software Confederation (SWC) Peer-to-peer network of independent cooperating applications (autonomous components) The only feasible solution for implementation of information systems of large organizations A powerful but not completely new software paradigm Powered by the progress of information technology

Software Engineering Advantages of Software Confederations Robust Easy to maintain (modify, enhance) Composed from rather autonomous parts from various sources Open Good for incremental development Support specific development techniques

Autonomous Components From system point of view peers (permanently active processes – applications) providing some permanent service(s) Can be developed or provided by third parties Can be legacy systems Tend to have complex interfaces based on rather complex problem-oriented messages/commands

Straightforward Structure of SWC Not satisfactory, user must know the structure of SWC G G G G – primary component gate

Structure of SWC (2) The user interface is transparent UI G G G User interface UI should be an autonomous component

Implementation Dependency of Gates If a gate G provides the full functionality of its component C, G must disclose at least the implementation philosophy if not implementation details (OO one or SQL oriented one) of C. Consequence: If the implementation philosophy of C is changed all the components communicating with C (partners) must be modified. But the set of partners can vary and unknown new partners can occur. Consequence: The modification of partners is a very difficult (if not unsolvable) task

Front-End Gates (FEG) Make an alternate access to the assigned application component May hide the implementation details and philosophy of given component Serve also as a wrapper to legacy or third party systems They must be message transducers  they can be based on the same tools and paradigms as UI. They can redirect messages, so they serve as Communication switches.

Structure of SWC (3) UI FEG G G

Autonomous Components Application Components (ApC) “Black boxes” Autonomous, partially independent May be also information systems; sometimes even software confederations Process messages/commands Communication Switch Components (CSwC) “White boxes” Easily configurable Cooperate with one or more ApC’s Translate messages/commands to another set of messages/commands

Opportunities for Maintenance Effort Reduction Reduction of the size of the newly written code –Making it smaller –Reuse or purchasing of the existing code (application, components, libraries, etc.) –Making most useful things first Simplifying of the newly written code –Software prototyping (also new techniques enabled by SWC’s) –Coarse grain decomposition

Reduction of the Size of the Newly Written Code Incremental development may lead to the smaller result – during the development process some of the functions may be recognized as useless

Reusing and Purchasing Existing software can often be integrated (and the staff is already familiar with it) Third party SW can be integrated quite easily (in many situations there already is some SW solving the problem)

Software Prototyping Allows to find the mistakes in the requirements specification faster – it is easier to rewrite a prototype than a full-featured application In SWC there is an opportunity to make new prototypes easier –Redirecting messages to a simulator –Using programmable user interfaces (CSS, XSLT)

Monitoring of Message Traffic Communication switches can: –Redirect the messages –Filter the messages –On request also store the messages with some system data into a db (log) for a later analysis Specific terms can be used for real-time SW (simulation with simulation time containing intervals of real time)

Domain Oriented Interface If the interface is problem domain oriented (instead of implementation oriented as it is now rather common), it is possible to make changes in the implementation of the components (also to exchange or update them) without the need to update all cooperating components.

SWC and Maintenance Confederations seem to be the only feasible solution for large and/or complex information systems for large organizations: –They allow to reduce substantially the maintenance effort and cost –The component maintenance activities tend to be local, i.e. the responsibility is let on the people having the best knowledge of the component