Is Product Owner participating as a member of Scrum Team in Nexus??

In Nexus, there is a single Product Owner for the entire Nexus. The person with the role of Product Owner is primarily aligned with the Nexus Integration Team. In the Nexus Guide's section on the Nexus Integration Team Members, it states that members of the Nexus Integration Team work across the Scrum Teams that form the Nexus to ensure they are able to detect dependencies, integrate the artifacts, and adhere to any standards that help develop the Integrated Increments. Just because the Product Owner is on the Nexus Integration Team doesn't mean that the Product Owner can't support all of the Scrum Teams in the Nexus.

Also consider that, in Nexus, Refinement is elevated to an event. As an event, there is a time and a place for the Refinement to occur. The Nexus Guide does state that the people who attend the Refinement are based on dependencies and uncertainty in the Product Backlog. If the team members of the Nexus performing further refinement have insufficient information about the Product Backlog Items that must come from the Product Owner, then the Product Owner would be an attendee at the Refinement event. Eventually, there would be enough of a shared understanding at the highest levels of granularity that the Scrum Teams would be able to break down items into work that one of the Scrum Teams can understand and deliver within a Sprint timebox.

The Nexus Guide can probably be a bit more clear about this relationship and how the Product Owner interacts with various Scrum Teams. However, the way I envision it is that the members of the Nexus Integration Team are on all of the Scrum Teams.

I am little bit confused about the Scrum Teams in Nexus in which there are no Product Owner, because the Product owner in include in a Nexus Integration Team. Is it necessary to describe this difference in Nexus Guide? OR may be change the name of the Scrum Team in Nexus as “Nexus Scrum Team”!!!

So I can see why you're a little confused but I believe it is because you're missing a very key point in the Nexus Guide:

Nexus roles, events, and artifacts inherit the purpose and intent attributes of the corresponding Scrum roles, events, and artifacts, as documented in the Scrum Guide (www.scrumguides.org).

This means that all roles, events, and artifacts apply in Nexus. The PO puts more emphasis in working closely with the Nexus Integration Team because if you've got 9 teams in the Nexus, it just isn't possible to be shared across 9 teams. Instead, the PO works directly with the NIT and the NIT's responsibility is to coach the scrum teams on the development, infrastructure, and architectural standards. The PO can still be available to any and all of the teams, but in order to put the focus on the backlog and product management, it makes more sense to work with the NIT and have the NIT radiate the information to the teams. 

Thomas' explanation hits the nail on the head, I just wanted to add a little extra. I've been using Nexus for the last 6 months and it's challenging to get it right but it works well.

As Curtis rightly pointed out, PO works in close collaboration with the Nexus Integration Team which consists of SM and one or more Nexus integration team members. 

According to Nexus guide,

Members of the Nexus Integration Team are often also members of the individual Scrum Teams in that Nexus. If this is the case, they must give priority to their work on the Nexus Integration Team; membership in the Nexus Integration Team takes precedence over individual Scrum Team membership.

and 

Coomon activities Nexus Integration Team might perform include coaching, consulting, and highlighting awareness of dependencies and cross-team issues. It might also perform work from the Product Backlog.

However, it is intended that Nexus team members are dedicated to integration than working in the teams that are developing independent product backlog items. Since there are multiple teams working on fairly independent refined product backlog items, the Nexus Integration Team becomes the primary information source for PO regarding the individual PBI. However, nowhere in the Nexus guide, it is mentioned and neither it is intended that the PO cannot or should not interact with individual scrum teams in Nexus. 

One bad practice I have observed during the formation of the Nexus Integration team is that people assume the Nexus Integration Team is the team of Team Leads. IT IS NOT. It is usually seen when the Integration Team Members are members of individual scrum teams. 

During Nexus Sprint Planning, appropriate representatives from each Scrum Team validate and make adjustments to the ordering of the work as created during Refinement events.

The statement above is also misconstrued and assumed that these team members (who are also part of the integration team) are the only ones that should be involved in the validation and prioritizing of PBIs. Over the period, this becomes a hierarchical structure, and the PO seems too distant for members of individual team members.

I am little bit confused about the Scrum Teams in Nexus in which there are no Product Owner, because the Product owner in include in a Nexus Integration Team.

The Scrum Teams in a Nexus have the same Product Owner, because they are working on the same product.

One product, one Product Backlog, one Product Owner, and many teams with a shared integration challenge.

I am little bit confused about the Scrum Teams in Nexus in which there are no Product Owner, because the Product owner in include in a Nexus Integration Team.

The Scrum Teams in a Nexus have the same Product Owner, because they are working on the same product.

One product, one Product Backlog, one Product Owner, and many teams with a shared integration challenge.

Ian is correct in what he states here.  The way I look at this is as follows: 

• Yes, a single scrum team includes the PO 
• A Nexus contains between 3 and 9 scrum teams
• A Nexus has a NIT
• Once the Nexus is formed (smallest amount of teams first, and then scale out further once Nexus is running smoothly) the PO & SM leave their location of a single scrum team to become members of the NIT
• The PO & SM collaborate with all scrum teams within their Nexus

As the PO & SM are now located within the NIT, their original scrum team could acquire two additional developers as a single scrum team typically has 10 or fewer people in it, which means a Nexus could have up to 92 people in it.

As a Nexus is not required for only 2 scrum teams because they are expected to easily work cohesively together, I assume that the second scrum team simply does not have their own PO & SM and share those roles with the first scrum team, meaning that the second team could have 10 developers compared with the first teams 8, or do the PO & SM move out of the first team allowing both teams to have 10 developers each?

@Scott Anthony Keatinge Being part of NIT does not mean that NIT members are outside the Scrum Teams. NIT Accountability can be imagined as a badge on your arm, if you have one, you have extra accountability towards the whole Nexus. However, that does not mean that you are removed from your Scrum Team and open a spot for an extra member.



Speaking about that, there is no max limit for Developers in Scrum Team, in the Scrum Guide there is only a hint, guidance, but not restriction:

The Scrum Team is small enough to remain nimble and large enough to complete significant work within a Sprint, typically 10 or fewer people. In general, we have found that smaller teams communicate better and are more productive. (...)

If in your context a Scrum Team with 15 Developers works fine, that is OK if you don't want to change this. However, based on experience, it is likely that smaller teams will work better together.

The only limitation within Scrum Team is connected to the SM and to the PO:

The Scrum Team consists of one Scrum Master, one Product Owner, and Developers.

In the context of Nexus, the limitation of one PO is elevated to the whole Nexus:

A Nexus has a single Product Owner who manages a single Product Backlog from which the Scrum Teams work.

Also, Nexus Guide put a constraint on Scrum Teams limit:

A Nexus is a group of approximately three to nine Scrum Teams that work together to deliver a single product.

If we summarize the above pieces of information, then a Nexus can consist of:

• One Product Owner
• 3-9 Scrum Masters (it is possible to defend also 1-10 limit, more below)
• 3-9 Scrum Teams

Within the Nexus, some people are also part of NIT. Because we have only one PO, he is part of NIT by design, and also a member of all Scrum Teams within a Nexus, therefore he or she should be involved in each Scrum event of each Scrum Team as a member of that team.

Regarding the Scrum Master accountability, Nexus does not introduce any new constraint, therefore it may be possible to have:

NIT SM: "(...) This Scrum Master may also be a Scrum Master in one or more of the Scrum Teams in the Nexus."

• one SM for the whole Nexus (one person that is "shared" for all Scrum Teams and the NIT)
• 9 SMs for the whole Nexus (one SM per each Scrum Team, one of those SMs take an SM accountability also in NIT)
• 10 SMs (one SM per each Scrum Team, and one developer or an extra person who take the accountability of SM within an NIT)

And any other mix within the above limits may be possible, depending on your individual context.

IMHO Scrum does not take a strong position about individual membership per se, it is possible to have a situation where one person is a Developer in one Scrum Team, and at the same time, he or she may be an SM in another Scrum Team and PO for other product and other Scrum Team(s). It may be not wise to do that, it is rather highly unsustainable. Nevertheless, it is possible, from each local Scrum Team perspective they have one SM, and one PO.