I am a Maximo expert with over 10 yrs of experience , have worked on many integration ,one of them was integrating Maximo with Caterpillar Integrated Procurement System (CAT IP ). You may check my profile on Linkedin which would have a relevant experience rather than this website.
As far I understand , you are a supplier and would like to get your purchase orders out of Maximo and may would like to submit your invoices, am I right ?
Frankly speaking , your project is missing much information, such , will Maximo push the data to your system ( DB ) ,or you will be pulling them our of your client's Maximo. The scope of work is not clear and hence bid might not be accurate. Let us have more insight about your requirements.
Best Regards
Amir