The analysis of an existing can be carried out in a number of ways, each with particular advantages and disadvantages:

Interviews - a face-to-face meeting between the users of the existing system and the person analysing the present system.

• Advantages: much more flexible than a questionnaire as the responses to questions can lead to new questions as the interview takes place and it is much easier to clarify any difficult points.
• Disadvantages: the interview can take time to set up and may involve travelling (although a telephone or video-conferencing could be used).  The person carrying out the interview will need to record the answers through the interview unless it is recorded.

Questionnaires - a series of questions which are answered by the users of the existing system.  They can be paper based or electronic.

• Advantages: quick to distribute to a number of users, either by post or email.  A range of closed and open questions can easily be asked.
• Disadvantages: some questions and/or answers my not be clear, particularly if the person who created the questionnaire is totally unfamiliar with the existing system.

Observation and inspection - the existing system is observed during it's normal operation and the recording system looked at.

• Advantages: the existing system can be observed throughout the whole input, processing and output cycle.  The recording system will show clearly what data is collected and what the information output is.
• Disadvantages: can be very time consuming. The observer may not full understand what they are observing without asking further questions.  It can be difficult to record the observations in a useful way.