Systems integration (SI), or enterprise application integration (EAI), consumes the lion's share of SI maintenance and development budgets. It is estimated that between 20% and 67% of the annual SI budget is devoted to building and maintaining integration, with the consensus seeming to be in the 30% to 40% range. ^{[78] [79] [80]} This is value-added work in only the most limited sense of the term. It is worth doing, and it provides some value; otherwise people wouldn't do it. However, the amount of effort it consumes is far out of proportion to what it could and should cost.

More important for the topic at hand, it has been estimated that 95% of this cost is attributable to semantics. ^[81] That number seems a bit high, even to a semantic fanatic like myself, but my experience would suggest that at least half the cost of integrating systems comes down to resolving semantic issues. In this chapter we cover the mechanics of systems integration; we will look at integration within your enterprise and integration with your trading partners. Then we'll look at two approaches that help with the semantic issues in integration: enterprise message modeling and semantic brokers.