Thanks to the effort of individuals in the End Point management team we have the Single Rule Evaluator and Software Update Agent diagnostics available (see https://kb.altiris.com for details) to help with the core PMS Inventory rules: IsApplicable and IsInstalled.
However lately I have found some problems not related to both rules, but a little upstream from them: namely in the Software Release and Service Pack inventory rules. So what are these rules for? They, much like the IsInstalled (let shorten this to IIR for Installed Inventory Rule) and AIR (Applicable Inventory Rule) are defined in the Inv_Inventory_rule data class table. So they also contain an InventoryRuleXml entry and are handle by the Inventory Rule agent on the managed computers.
What differs though is that both of these rule sets (and resulting data classes) are then used by Patch Management Solution to create the intersect collection, which is like a SQL inner join between the user select collection (content) and the Service Pack or Service Release collection (content, again ;).
Now I suspect this is not very clear, so let's look at this.
This screen shot samples shows us the Software Release and Service Packs requirements for Office 2003 update KB947319. This means that a collection for Office2003-KB947319 exist in the NS and contains all resources that have reported Software Release 'Office 2003 - English' and Service Pack data 'Office 2003 SP3 - English'.
So this is something worth bearing in mine when troubleshooting Patch Management execution error: is the computer targeted correctly by the NS or not?
My fresh experience tells me that this is not always the case, but I'm sure this was just a one off ;).