You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Prime_minister

Context:
In parliamentary systems fashioned after the Westminster system, the prime minister is the presiding and actual head of government and head of the executive branch. In such systems, the head of state or the head of state's official representative (i.e. the monarch, president, or governor-general) usually holds a largely ceremonial position, although often with reserve powers.

Question:
What is a parliamentary model on which other systems have been based?

Westminster system