Download full-size image from Pinterest. Must/mustn't Use must + infinitive without to. Must is a modal verb, and modal verbs are followed by an infinitive without to.. I must go to the doctor. (NOT I must to go to the doctor.; No -s. Modal verbs don't add -s after he/she/it.. He must come with us. (NOT He must comes with us.; Use must/mustn't in negatives and questions In the bool query, we have the following fields: must. must_not. should. filter. Must is analogous to the boolean AND, must_not is analogous to the boolean NOT, and should is roughly equivalent to the boolean OR. Note that should isn't exactly like a boolean OR, but we can use it to that effect. And we'll take a look at filter later on. In your examples, "should" represents a suggestion for action, while "must" represents a command where you want the listener to obey you. Often "should" is used instead of a direct request. "Please pick up your clothes from off of the floor." "You should pick up your clothes from off of the floor." Must is not really a verb, but it is a necessity which can be expressed as a verb as have to. Therefore, putting "must" into the past tense would be expressed as had to. For instance, I must go to the store today. It would be, I had to go to the store yesterday. it does express the necessity of going to the store. 1. To talk about obligations/necessit ies. The most common usages of must and have to is to talk about obligations or necessities (situations/things that are quintessential).. MUST. Use MUST to talk about an obligation that is internal. (When an obligation is internal (you understand the importance of something and know it is not the right thing to avoid it), use MUST to talk about it. Further, the word 'must' remain the same in all the three tenses, whereas have to becomes 'had to' and 'will have to', in the past tense and future tense respectively. The main difference between must and have to, is that while must is a modal verb, have to is a semi-modal verb, in the sense that as a modal verb it is used along Must. 'Must' is the basic and most direct way of saying something is compulsory. It means you have no choice but to do (or not do) an action. We can only use 'must' in the present form to describe a general or permanent obligation, or an obligation in the near future. Use 'must' to express something that you or a person feels is necessary. This form is used only in the present and future. You don't have to arrive before 8. They didn't have to work so hard. The negative form of 'have to' expresses the idea that something is not required. It is, however, possible if so desired. She mustn't use such horrible RFC 2119 gives the following definitions: MUST This word, or the terms " REQUIRED " or " SHALL ", mean that the definition is an absolute requirement of the specification. MUST NOT This phrase, or the phrase " SHALL NOT ", mean that the definition is an absolute prohibition of the specification. SHOULD This word, or the adjective " RECOMMENDED It should (but does not) work liek that: bool combine via OR must and filter parts; first must select by query; filter uses bool which combines by OR must andmust_not` But this behaves like must combined with must_not via AND clause. E.g. when I removed "must" or "must_not" query works. How change query to combine "must" with "must_not" via OR 72wxn.