When you file a patent, you usually don't file a patent because someone else is doing the (paper)work for you. A similar thing can happen with other paperwork or places where you usually have to appear in person. In most cases you can delegate the work and sign a power of attorney (in German "Vollmacht"), i.e., something that grants the person mentioned in that paper the power to act or sign in behalf of you. The person acting can represent multiple other persons and he/she may switch roles during the process.
This reminded me of trusted contexts in DB2. When a trusted context is used that special user can act for others by switching the userid. As with legal matters, there are also some strings attached to trusted contexts and this overview page has gives you an introduction to what to expect.
BTW: This posted was written on behalf of Henrik.