wehub-resource-sync
80 lines
4.4 KiB
Markdown
80 lines
4.4 KiB
Markdown
# Big Picture EventStorming
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We started the domain exploration with sticky notes and a pen. What turned out to be the first discovery,
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was the **close-ended book holding** process:
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Let's briefly walk through it:
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- A **Regular Patron** can **place a book on a close-ended hold**
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- A **Regular Patron** might **reach a maximum holds number** after a **hold is placed**
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- A **Regular Patron** can either **cancel the hold** or **check out the book**
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- While the book is **checked out** the **hold is completed** and so the **returning process** starts
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- Whenever a new day starts, we check the **daily sheet** if a hold is not hanging for too long. If so,
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the **book hold is expired**
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On the high level, the process looks clear now, but it does not work the way, that all of us
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interpreted each word written no the sticky note similarly. That's why we established some definitions:
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Similar discoveries were made around **open-ened book holding** process:
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- A **Researcher Patron** can **place a book on an open-ended hold**
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- A **Researcher Patron** can either **cancel the hold** or **checkout a book**
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- While the book is **checkedout** the **hold is completed** and so the **returning process** starts
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- Within the **open-ended holding** a **hold** cannot **expire** (mind the lack of **hold expired** event)
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All right. These two processes are very similar. The part that they have in common, and we know nothing about
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it yet is called the **book returning process**:
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Here's what you see there described with words:
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- **Any Patron** can **return a book**
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- If the **checkout is overdue**, it is being unregistered as soon as the **book is returned**
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- In the moment of **returning a book** we start the process of **Fees application**
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- From the moment of **book checkout**, a patron might not return the book on time. Whenever a **new day starts**
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we check the **daily sheet** find and **register overdue checkouts**
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Wait, but what is this **checkout**?
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_- OK, now tell me what is this fee application process_
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_- Nope, it is not relevant by now, will get back to it later_
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_- But wait, why? Shouldn't you get the full picture from the storming?_
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_- Yes, but remember, the time has its cost. You always need to focus on the most relevant (at this moment) business part.
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I promise to get back to this at the next workshop._
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_- Fair enough!_
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Fundamental question that raises now is _where do these books come from?_ Looking again at the domain description,
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we have a notion of a **catalogue**. We modelled it accordingly:
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Here's what happens:
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- A **library employee** can add a book into a catalogue
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- A specific **book instance** can be **added** as well, thanks to which it can be made **available** under some not
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defined yet policy
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- Both **Book removed from catalogue** and **Book instance removed from catalogue** are marked with **hot spots**,
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as they became problematic. We left answering those problems for the future.
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There is one interesting thing we can spot in this simple **catalogue** flow. **A book** is not the same **book** that
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we had in previous processes. To make things clear, let's have a look at new definitions:
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Spotting such differences helps us in drawing linguistic boundaries, that are one of the heuristics for defining
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**bounded contexts**. From this moment on, we can assume that we have at least two **bounded contexts**:
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* **lending** - context containing all business processes logically connected with book lending, including holding,
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checkout, and return
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* **catalogue** - contexts for cataloguing books and their instances
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__More information on bounded contexts' defining will be added soon__
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This is more or less where the first iteration of _Big Picture EventStorming_ finished. After this phase
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we had a good understanding of how library processes work on high level, and, what is an invaluable outcome,
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we got the **ubiquitous language** including well described definitions, and initial **bounded contexts**. |