You can subscribe to that resource calendar and see how many bookings currently exists.

Regarding the maximum number of resources available, I guess you can document it somewhere else (internal documentation). This really depends of the resource purpose.

this is not the point, users have to see how many ressources are available in a visible error and in process of booking.

just to subscribe to a resource would be helpfull, but its only the half-way. There must be another solution, directly from booking window.

Could you please give an example of such resource usage?

I can imagine some cases, but I think that in most cases, such approach is not the right way to manage that particular resource.

Also think about the cases, in which at the start time of booking, number of available resources might be bigger then at the end of the planned "event" i.e. booking. At which point in time the number should be counted? Not to mention that it could be quite complicated with various scenarios of booking overlapping.

I will give you you one example:
If you have a lot of laptops that you treat them as one resource, that might be the wrong approach. Instead, you can create separate resources per laptop.

Why not? what else is this counting good for?

Example: Students have to make a film/report. There are 20 Cameras of the same type. One class has 12 Students the other 14. There are 2 lecturers, who want to use the same Resource at the same time. As you can see its impossible. But if a lecturer has information about spare cameras, he can plan his lecture with less.

The same procedure with tablets/notebooks or anything else (resource is everytime the same type/kind)

SOGo is really good, but it might not be good solution for inventory/resource management (example with cameras).

Imagine the following:

• Student1 has booked camera from 02/02/2014 - 03/02/2014 (i.e. 2 days)
• Student2 has booked second camera from 03/02/2014 - 04/02/2014 (i.e. 2 days)
• Student3 wants to book camera from 01/02/2014-05/02/2014 (i.e. 5 days with overlap with Student1 and Student2)

Question: What number of camera booking you would expect from SOGo when Student3 attempts to book it: 0 or 1 or 2?

So, I would say that you have 2 options:

• try to manage cameras as independent resources (e.g. camera1, camera2, etc)
• either try to use another solution (different product)

Although we don't use SOGo as a ressource planning system, displaying the number of available resources of a kind at some point in time is mandatory in order to make sense at all.

Application of some basic set theory yields the following answer: n-1 (with n being the total number of cameras in the pool). If you want to make it bullet-proof, include the hours.

The iterative approach would be obviously to build a set of numbers of cameras available per day over the requested period and return the smallest number of the set as the number of available cameras (that cover the entire period) for the applicant.