The Essential Guide to Technical Specifications for Your Expo-Based Native Mobile App

A clear understanding of a project is paramount, especially in mobile app development. While some industries operate under universally recognized quality standards, if your field lacks such precise norms, a Technical Specification (TS), also known as a Statement of Work (SoW), is the best way to outline your requirements for a mobile application. This article will explain what a TS is, who needs one (and who might not), and what it should contain, particularly when developing native mobile apps with Digital Kitty using the Expo framework.

What is a Technical Specification?

A Technical Specification (TS) is a document detailing all requirements for a mobile application. Developing a TS helps you, the client, to formulate and record precisely how you envision the final app. For our team at Digital Kitty, it allows us to accurately estimate the resources needed for your Expo-based native app and to fully understand your vision.

The term "Technical Specification" can be interpreted broadly. Consider this everyday example: Is "Paint the fence green" a TS? Not really; it's more of a general vision. A proper TS would be: "Paint the fence with 'Pro Paints' brand, shade 'Forest Green,' in two coats, each 3mm thick. Start painting from the gate and finish at the post. Allow at least 4 hours drying time between coats. Work to be completed within 24 hours."

Similarly, for mobile app development, a TS is a document reflecting the app's goals, requirements, the technologies involved (like React Native with Expo), development methods, approval processes for interim and final results, deadlines, and your ultimate vision for the app.

A TS facilitates clear communication between you and Digital Kitty. In case of any disagreements, the TS serves as the reference point to resolve them. Ideally, the TS becomes an annex to the main development contract.

When is a Technical Specification Needed for Your Mobile App?

It largely depends on your project's scope. For very small tasks, if you have full confidence in our team and believe there will be no misinterpretation of your requirements for an Expo app, a less detailed brief might suffice.

However, if you need to develop a technically complex native mobile application with significant investment, a detailed TS outlining all crucial requirements is highly recommended. This is also true for projects with strong creative or design components; for mobile apps, specific UI/UX requirements must be documented to ensure we deliver exactly what you envision.

When Might a Full Technical Specification Not Be Essential?

A TS isn't always the only path to an efficient and timely result. Sometimes, an overly rigid TS can limit creativity or become confusing.

This might happen if:

• You, as the client, are still exploring the app's requirements. In such cases, a more agile approach to the TS is used. The specification is formulated iteratively as the app development progresses and the vision for the final product becomes clearer. At Digital Kitty, we can start with a Product Vision document and build out details.
• You have a long-standing, trusted relationship with Digital Kitty and are confident that there will be no misunderstandings, and the Expo app will be developed to your satisfaction.
• The mobile app project is small with standard functionality that is well understood by both parties.

In some projects, a Product Vision document can be sufficient instead of a full TS initially. A Product Vision is the starting point for any mobile app project built with Expo. It provides an overview of the app, its requirements, goals, and objectives.

However, be aware that working without a detailed TS carries risks. Before deciding against a comprehensive specification, assess the potential impact of work not being completed or being completed incorrectly.

Benefits of a TS for You (The Client)

A Technical Specification is a vital tool in mobile app development. When you prepare a detailed TS for your Expo-based native app (or have Digital Kitty assist you), you achieve several goals:

• Estimate the Budget: Accurately calculating the cost of custom mobile apps is impossible without clear requirements. A TS helps define these requirements, leading to a realistic budget and timeline for your Expo app.
• Structure Information: You come to Digital Kitty with specific needs for your mobile app. These requirements might stem from various departments – technical, marketing, analytics, sales – each with its own objectives. The app must consolidate and meet all these demands. A TS helps organize this information into clear tasks.
• Assess Our Competence: Through the process of creating or reviewing a TS, you can gauge Digital Kitty's expertise with Expo and native app development. Often, clients who engage us for TS preparation plan to continue the development with us. A clear, well-structured TS builds confidence.
• Safeguard Against Misunderstandings: If, for any reason, issues arise during the app's implementation, a well-drafted TS allows any new team members (or even a different agency, though we aim for long-term partnerships!) to quickly understand the task and get up to speed. Furthermore, a TS enables stakeholders without a technical background to verify that the completed Expo app meets the documented requirements.

Who Creates the Technical Specification?

In our experience at Digital Kitty, there are three main approaches:

1. The Client Writes the TS: You come to us with a fully prepared TS detailing your requirements for the Expo app. We review it, estimate the time and cost, and if we agree, development begins.
2. Digital Kitty Writes the TS: You describe the goals of your mobile app and its desired functionality. Our business analysts then study and structure these requirements. They gather necessary information, potentially interview your team members, clarify tasks, propose solutions (leveraging the strengths of Expo), and get your approval.
3. Collaborative TS Development: This is similar to the previous point but with a different distribution of responsibilities. Digital Kitty doesn't gather all information independently; you actively assist. After initial briefings, we conduct a series of interviews to discuss and finalize the nuances of your Expo app development.

The best approach depends on your specific needs and project goals. While Digital Kitty has extensive experience creating TS documents for numerous Expo apps, only you possess the deep internal knowledge of your business and precise requirements.

And one more thing: don't feel obligated to use highly technical jargon in your initial brief. You can describe your desired mobile app in your own words. This is where a Product Vision document, as mentioned earlier, can be very helpful. Simply come to us with a document outlining your core requirements and wishes.

Can You Use a Ready-Made Template from the Internet?

You could try using an online template as a base, but consider these points:

• There are countless templates, and finding one suitable for an Expo-based native mobile app can be challenging. You might spend a lot of time sifting through them and trying to piece something together.
• Every mobile app is created to achieve specific business goals. Using a generic template might lead you to copy someone else's objectives and overlook your own unique needs.
• A template might contain many irrelevant sections for your specific Expo app or lack crucial requirements unique to your project.

At Digital Kitty, when we prepare a TS, we first clarify your objectives and the purpose of your mobile app. Then, we write the TS based on the gathered information and your specific requirements for an Expo-based solution.

What to Look for When Reviewing a TS for Your Expo App

Remember the primary purpose of a TS: both parties must understand each other correctly. Here are a few recommendations:

Unambiguous Wording

A phrase like "Make a beautiful app" can be interpreted differently by you and by our developers. To avoid discrepancies, it's best to avoid subjective adjectives like "beautiful," "good," "high-quality," "fast," or abstract examples like "The app must load quickly." How quickly is "quickly"? Such statements are open to individual interpretation. The more precisely the technical specification is described, the better the outcome.

Instead of ambiguous phrases, use clear, measurable ones:

• Ambiguous: "The app should have a modern design."

• Clear: "The app design should follow Apple's Human Interface Guidelines for iOS and Google's Material Design principles for Android, incorporating the color palette specified in the brand guide (HEX codes: #XXXXXX, #YYYYYY). Key user flows should be benchmarked against [App X] and [App Y] for ease of use."

• Ambiguous: "User data must be secure."

• Clear: "User authentication will be handled via Firebase Authentication. All API communications transmitting sensitive data (e.g., user credentials, payment information) must use HTTPS. Data at rest on the device (if any) should be encrypted using AES-256."

Glossary

The TS is for both you and Digital Kitty. Therefore, there should be no unfamiliar words for anyone. Specific development terms related to Expo or React Native should be explained in a glossary if they are not commonly understood. Use plain language.

This principle also works the other way around. If your business has specific terms that might be unclear to us, please clarify them. Digital Kitty specializes in Expo app development, but the nuances of your business might not be immediately obvious.

Examples and References

Anything that can be demonstrated, should be. When working on the TS, refer to existing mobile apps. Show us apps or specific features you like. Such references (screenshots, links to app store pages) help visually convey what you want. For instance, if an app uses a great font or has an intuitive navigation flow, show it with a screenshot or a short screen recording. The more visually the task is presented, the easier it is to implement.

What Must Be in a Technical Specification for an Expo Mobile App?

Let's outline the key sections of a TS for a native mobile app developed with Expo:

1. Introduction and Project Goals

• About Your Company: Briefly describe your company, its activities, and target audience.
• App Purpose: Clearly state the problem the mobile app solves or the opportunity it addresses. What are the primary goals (e.g., increase sales, improve customer service, streamline operations)?
• Target Audience for the App: Define the primary users of the app, their demographics, needs, and technical proficiency.
• Success Metrics: How will the success of the app be measured? (e.g., number of downloads, active users, conversion rates).

2. General App Requirements

• App Name: The proposed name for the application.
• Platforms: Specify target platforms (iOS, Android). With Expo, this is often both, but confirm.
• App Type: e.g., e-commerce, social networking, utility, enterprise tool.
• Monetization Strategy (if any): e.g., paid app, in-app purchases, subscriptions, ads.
• Core Technology: Specify that the app will be developed using React Native with the Expo framework. Mention any specific reasons for this choice if relevant to functionality.

3. Functional Requirements

This is the heart of the TS, detailing what the app will do.

• User Roles and Permissions: Define different types of users (e.g., admin, registered user, guest) and their respective access rights and capabilities.
• Feature List: A comprehensive list of all features. For each feature:
  • A clear description of its purpose and functionality.
  • User stories (e.g., "As a [user role], I want to [action] so that [benefit]").
  • Acceptance criteria (how to verify the feature is working correctly).
• User Scenarios (Use Cases): Describe how users will interact with the app to achieve their goals. Detail the step-by-step flow for key tasks. For example, for an e-commerce app:
  1. User Action: Taps on a product category.
  2. App Response: Displays a list of products in that category.
  3. User Action: Selects a product.
  4. App Response: Shows detailed product information screen. (And so on for adding to cart, checkout, etc.)

4. Non-Functional Requirements

These define how well the app should perform its functions.

• Performance:
  • Screen load times (e.g., critical screens should load in 2 seconds on a 4G connection).
  • Responsiveness to user input.
  • Data handling capacity (if applicable).
• Usability & Accessibility (UX/UI):
  • Adherence to platform design guidelines (Apple Human Interface Guidelines, Android Material Design) to ensure a native feel, even with Expo.
  • Requirements for accessibility (e.g., WCAG AA compliance, support for screen readers, dynamic font sizes).
  • Overall navigation structure and information architecture.
• Security:
  • Data encryption (in transit and at rest).
  • Authentication and authorization mechanisms.
  • Protection against common mobile vulnerabilities.
  • Privacy policy considerations and data handling (e.g., GDPR compliance for European users).
• Scalability (if applicable): How the app should handle growth in users or data.
• Offline Support: Specify if the app needs to function without an internet connection and how data synchronization should occur.
• Push Notifications: Requirements for using services like Expo Push Notifications.
• Localization/Internationalization: If the app needs to support multiple languages or regions.

5. Design and Branding

• Brand Guidelines: If you have an existing brand book, it should be provided (logo, color palette, typography).
• App Aesthetics: Desired look and feel, mood boards, or references to other apps.
• Screen Wireframes & Prototypes: These are crucial. They should illustrate the layout, navigation, and flow for all key screens. Digital Kitty can help create these.
• UI Kit: A collection of reusable UI components (buttons, forms, cards, etc.) that will be used in the app. This ensures consistency and speeds up development with React Native/Expo.
• Animations & Transitions: Specify any desired animations or screen transitions.

6. Technical Requirements & Architecture

• Expo Specifics:
  • Mention reliance on Expo SDK and its libraries.
  • Use of EAS (Expo Application Services) for builds, updates, and submissions, if planned.
• API Integrations: List all third-party services the app will integrate with (e.g., payment gateways, social media, mapping services, backend APIs). Provide API documentation if available.
• Backend Requirements (if applicable): If Digital Kitty is also developing the backend, or if there are specific requirements for an existing backend.
• Data Storage: Local device storage (e.g., AsyncStorage, SQLite via Expo) and server-side database requirements.
• Analytics: Specify what user activities to track and which analytics platforms to integrate (e.g., Firebase Analytics, Amplitude, or custom solutions via Expo).

7. Content

• Content Sources: Who provides the text, images, videos, and other content for the app?
• Content Format: Specify formats and resolutions for media assets.
• Content Management: How will dynamic content be updated (e.g., via a CMS)?

8. Testing and Quality Assurance

• Testing Scope: Types of testing to be performed (functional, usability, performance, security, compatibility across devices/OS versions).
• Target Devices/OS Versions: Specify the range of devices and OS versions the Expo app must support.
• Beta Testing: Plans for beta testing phases and feedback collection.

9. Deployment and Maintenance

• App Store Submission: Who is responsible for preparing store listings (text, screenshots, keywords) and submitting to Apple App Store and Google Play Store (potentially using EAS Submit).
• Post-Launch Support: Requirements for ongoing maintenance, bug fixes, and potential future updates (e.g., compatibility with new OS versions, updates to Expo SDK).

10. Project Management and Delivery

• Timeline and Milestones: Expected project duration and key deliverables.
• Communication Plan: How often will updates be provided, preferred communication channels.
• Acceptance Criteria for Final Delivery: How the final app will be evaluated and approved.

The Process of Creating a Technical Specification at Digital Kitty

Creating a TS is often the first major step in development. Collaboration between you and our specialists is key. This typically involves iterative discussions and interviews. Our goal at Digital Kitty is to fully understand your expectations for the future Expo-based mobile app.

During meetings, we clarify project requirements: goals, tasks, functionality, and the need for integrations. Once all information is gathered, our team begins preparing the TS. A system analyst designs the app's architecture, and a technical lead (proficient in React Native and Expo) plans the technical implementation. We then present the draft TS to you, discuss it, and iterate until it's approved. Once the TS is ready, we can proceed with the actual development.

The team involved in preparing the TS typically includes an analyst, project manager, UI/UX designer, and a lead developer specializing in Expo. The time to create a comprehensive TS can range from two weeks to two months, depending on the app's complexity and scope.

In Conclusion

Above all, a Technical Specification is a tool that should facilitate the development of your mobile application. If you have a ready TS, Digital Kitty will study it and provide you with an estimate for the timeline and budget for your Expo app. If you only have a vision for your project, we can work with that too, or help you formalize it into a detailed TS.

If a full, upfront TS doesn't suit your needs and you prefer a more agile development approach, we'll discuss this and can develop your Expo app in sprints. This means dividing the work into short intervals, at the end of which we present a concrete result.

Our priority at Digital Kitty is to ensure that your Expo-based native mobile app effectively serves your business goals.