SOA is an architectural style. And building architecture is a Top-Down process and not Bottom-Up. The most compelling reason for saying that Web Services are not SOA is that they are technical stuff, often built with a Bottom-Up APPROACH. Building a Bottom-UP SOA is a wrong approach and might lead to an architecture with a lot of REDUNDANCY or maybe no architecture at all.

However, the result of building SOA only Top-Down could be PERCEPTUAL Architecture building with no run TIME artifacts, so some SOA efforts should be Bottom-Up efforts. To sum up: Initially SOA is a Top-Down approach but pragmatic approach requires mixing Top-Down approach with Bottom-Up approach.

SOA is an architectural style. And building architecture is a Top-Down process and not Bottom-Up. The most compelling reason for saying that Web Services are not SOA is that they are technical stuff, often built with a Bottom-Up approach. Building a Bottom-UP SOA is a wrong approach and might lead to an architecture with a lot of redundancy or maybe no architecture at all.

However, the result of building SOA only Top-Down could be perceptual Architecture building with no run time artifacts, so some SOA efforts should be Bottom-Up efforts. To sum up: Initially SOA is a Top-Down approach but pragmatic approach requires mixing Top-Down approach with Bottom-Up approach.