docs: add motivation part

README.md

@@ -66,11 +66,11 @@ In many organizations, legacy systems still rely on hundreds of cron jobs runnin
 
 ## **A Lightweight and Self-Contained Solution**
 
-While Cron is lightweight and suitable for simple scheduling, it doesn't scale well for complex workflows or provide features like retries, dependencies, or observability out of the box. On the other hand, tools like Airflow or other workflow engines can be overly complex for smaller projects or legacy environments, with steep learning curves and burdensome to maintain. Dagu is designed to be easy to use, self-contained, and require no coding, making it ideal for smaller projects.
+While Cron is lightweight and suitable for simple scheduling, it doesn't scale well for complex workflows or provide features like retries, dependencies, or observability out of the box. On the other hand, tools like Airflow or other workflow engines can be overly complex for smaller projects or legacy environments, with steep learning curves and burdensome to maintain. Dagu strikes a balance: it's easy to use, self-contained, and require no coding, making it ideal for smaller projects.
 
-## **A Tool for Developers of Small Projects**
+## **Built By and For In-House Developers**
 
-Dagu's design philosophy stems from the real-world experience in managing complex jobs across diverse environments, from small startups to enterprise companies. By focusing on simplicity, transparency, and minimal setup overhead, Dagu aims to make life easier for developers who need a robust workflow engine without the heavy lift of a more complex tool.
+Dagu's design philosophy stems from the real-world experience in managing complex jobs across diverse environments, from small startups to enterprise companies. By focusing on simplicity, transparency, and minimal setup overhead, Dagu aims to make life easier for in-house developers who need a robust workflow engine without the heavy lift of a more complex tool.
 
 ## **Community**
 
@@ -330,19 +330,51 @@ steps:
     depends: step1
 ```
 
-### JSON processing
+### Conditional DAG
 
-You can reference the nested JSON data using the syntax `${INPUT.key}`:
+You can add conditional logic to a DAG:
 
 ```yaml
-params:
-  - INPUT: '{ "name": "John", "age": 30 }'
 steps:
-  - name: John's age
-    command: echo ${INPUT.name} is ${INPUT.age} years old
+  - name: monthly task
+    command: monthly.sh
+    preconditions:
+      - condition: "`date '+%d'`"
+        expected: "re:0[1-9]" # Run only if the day is between 01 and 09
+```
+
+### Scheduling
+
+You can specify the schedule with cron expression:
+
+```yaml
+schedule: "5 4 * * *" # Run at 04:05.
+steps:
+  - name: scheduled job
+    command: job.sh
+```
+
+Or you can set multiple schedules.
+
+```yaml
+schedule:
+  - "30 7 * * *" # Run at 7:30
+  - "0 20 * * *" # Also run at 20:00
+steps:
+  - name: scheduled job
+    command: job.sh
 ```
 
-It will write `John is 30 years old` to the log (stdout).
+If you want to start and stop a long-running process on a fixed schedule, you can define ``start`` and ``stop`` times:
+
+```yaml
+schedule:
+  start: "0 8 * * *" # starts at 8:00
+  stop: "0 13 * * *" # stops at 13:00
+steps:
+  - name: scheduled job
+    command: job.sh
+```
 
 ### Calling a sub-DAG
 
@@ -370,9 +402,22 @@ steps:
 THe parent DAG will call the sub-DAG and write the output to the log (stdout).
 The output will be `Hello from sub-dag`.
 
-More examples can be found in the [documentation](https://dagu.readthedocs.io/en/latest/yaml_format.html).
+#### Running a docker image
+
+You can run a docker image as a step:
 
-### Complex examples
+```yaml
+steps:
+  - name: hello
+    executor:
+      type: docker
+      config:
+        image: alpine
+        autoRemove: true
+    command: echo "hello"
+```
+
+### A bigger example
 
 A typical data pipeline for DevOps/Data Engineering scenarios:
 
@@ -450,6 +495,8 @@ steps:
       - send_report
 ```
 
+More examples can be found in the [documentation](https://dagu.readthedocs.io/en/latest/yaml_format.html).
+
 ## **Running as a daemon**
 
 The easiest way to make sure the process is always running on your system is to create the script below and execute it every minute using cron (you don't need `root` account in this way):

docs/source/index.rst

@@ -23,6 +23,9 @@ A powerful, self-contained Cron alternative with a clean Web UI and a `declarati
 Quick Start
 ------------
 
+:doc:`motivation`
+   The motivation behind Dagu.
+
 :doc:`installation`
    How to install Dagu.
 
@@ -48,6 +51,12 @@ Quick Start
 :ref:`changelog`
    History of changes.
 
+.. toctree::
+   :caption: Motivation
+   :hidden:
+
+   motivation
+
 .. toctree::
    :caption: Installation
    :hidden:

docs/source/motivation.rst

@@ -0,0 +1,19 @@
+.. _MOTIVATION:
+
+Motivation
+==========
+
+Why we built Dagu
+------------------
+
+In many organizations, legacy systems still rely on hundreds of cron jobs running across multiple servers. These jobs are often written in various languages like Perl or Shell scripts, with implicit interdependencies. When one job fails, troubleshooting requires manually logging into servers via SSH and checking individual logs. To perform recovery, one must understand these implicit dependencies, which often rely on tribal knowledge. Dagu was developed to eliminate this complexity by providing a clear and understandable tool for workflow definition and dependency management.
+
+A Lightweight and Self-Contained Solution
+------------------------------------------
+
+While Cron is lightweight and suitable for simple scheduling, it doesn't scale well for complex workflows or provide features like retries, dependencies, or observability out of the box. On the other hand, tools like Airflow or other workflow engines can be overly complex for smaller projects or legacy environments, with steep learning curves and burdensome to maintain. Dagu strikes a balance: it's easy to use, self-contained, and require no coding, making it ideal for smaller projects.
+
+Built By and For In-House Developers
+-------------------------------------
+
+Dagu's design philosophy stems from the real-world experience in managing complex jobs across diverse environments, from small startups to enterprise companies. By focusing on simplicity, transparency, and minimal setup overhead, Dagu aims to make life easier for developers who need a robust workflow engine without the heavy lift of a more complex tool.