Enterprise Software (ES):
It seems to me that you need to delimit and define the scope of the ES for your specific analysis. Often this is done by exclusion, like:
* IT solution developed to support processes of a large business domain, like an area of human/social administration (employee, customer / taxation, security, environment) or product manufacturing and control (purchase, stocks).
* typically you want to excludes general office and infrastructure products (text processing, DB etc) and exclude tools to develop IT solutions (languages, libraries, IDEs etc).
* often you also want to exclude "shrink wrapped" ES solutions (like commercial CRM, ERP)
* when focusing on custom developed ES systems and the specific problems of these related to large scale project administration and SW design, construction, deployment, operation & maintenance