Endemics have priority over natives and exotics are eradicated :)

Endemics AND Red Data/protected species have priority over the rest.

Value is one of the basic criteria when creating conservation plan. All conservation actions (preventive and interventive) should be based on thorough research. This research would include items history, material and function in society (as well as all other possibilities like previous restoration, damage, etc.). This function, then, can be perceived as value.

Value is not something what item have from the beginning. Value is given by people. By people who created the item and also by "us" - conservers, historians and museum curator. Consequently value is variable in time. It is important to evaluate past and current values and create conservation plan on acquired results. Original values, argumentatively, should have priority, but in some cases contemporary values may be preferred (e.g. if only one or few items survived).

Furthermore, there is something called multiplicity of values. Every object have more values. In the most simple examples there is historical value and esthetic value (examples of other values may be religious, social, scientific etc.). Historical value contains history of the object. Esthetic value contain esthetic and artistic qualities. When talking about working objects (like industrial machinery, trains,...) there is also technological qualities.

If object is important for its age and overall historical value, conservation plan should be very careful and should aim for maximal preservation of the object and its fabric and structure.

If object is important for its aesthetic values, conservation plan should aim at restoring the object to its "formal glory", so it can be perceived by visitors in its artistic totality.

If object is important for its technical qualities, conservation plan should aim not only to restore the object, but (if possible) to restore it to working conditions, because to fully understand these types of object, it is important to se the machine in action. Sounds, smells, vibration, visual effect are integral part of the object and should be presented.